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Linux_Administrator_Daily_Tasks
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| ------------------------------------------------------------------------------------------ | |
| #CLI shortcut keystrokes(linux&MAC) | |
| Ctrl+L: Clear the screen. This is similar to running the “clear” command. | |
| Ctrl+C: Interrupt (kill) the current foreground process running in in the terminal. This sends the SIGINT signal to the process | |
| Ctrl+Z: Suspend the current foreground process running in bash. This sends the SIGTSTP signal to the process. To return the process to the foreground later, use the fg process_name command. | |
| Ctrl+D: Close the bash shell.This is similar to running the exit command | |
| Ctrl+L: Clear the screen. This is similar to running the “clear” command. | |
| Ctrl+S: Stop all output to the screen. This is particularly useful when running commands with a lot of long, verbose output, but you don’t want to stop the command itself with Ctrl+C. | |
| Ctrl+Q: Resume output to the screen after stopping it with Ctrl+S. | |
| Ctrl+A or Home: Go to the beginning of the line. | |
| Ctrl+E or End: Go to the end of the line. | |
| Alt+B: Go left (back) one word. | |
| Alt+F: Go right (forward) one word. | |
| Ctrl + U to clear up to the beginning | |
| #multiple virtual consoles | |
| CTRL + ALT + F1-F8 | |
| ------------------------------------------------------------------------------------------------------------------------------------------------- | |
| $ bash --version | |
| ------------------------------------------------------------------------------------------ | |
| /etc #configuration files on the system | |
| /etc/hosts #maps hostnames to IP addresses | |
| /etc/skel #files copied to each user's home | |
| /usr #user by user and supersuser accounts.Stores application programs | |
| /usr/bin #executables used by users, in user's PATH statement | |
| /usr/sbin #executables used by superusers | |
| /usr/local #applications which are not part of linux | |
| #applications installed after initial linux installation,in user's PATH statement | |
| #administrative applications installed after initial linux installation | |
| /usr/local/bin | |
| /usr/doc #the default location for application documentation is in a directory named for the application | |
| /var #stores log files, mails and other data | |
| /var/spool #mail & printing files | |
| /var/tmp #data that should persist across reboot | |
| /var/log #log files | |
| /var/log/anaconda.log - While installing Linux, all installation related messages are stored in this log file | |
| /var/log/audit/ - This subdirectory contains logs information stored by the Linux audit daemon (auditd) | |
| /var/log/auth.log - user logins,such as password prompts | |
| /var/log/boot.log - Contains information that are logged when the system boots | |
| /var/log/cron - Whenever cron daemon (or anacron) starts a cron job, it logs the information about the cron job in this file | |
| /var/log/debug #debugging information from the Ubuntu system and applications | |
| /var/log/daemon.log - display server, SSH sessions, printing services, bluetooth | |
| /var/log/dmesg - Contains kernel ring buffer. This file is overwritten when the system is rebooted. | |
| /var/log/faillog -failed user login attempts. ssh(used for remote login), su(to switch users), at, cron (both used for scheduling tasks) use PAM modules for authentication | |
| /var/log/kern.log - Contains information logged by the kernel. Helpful to troubleshoot a custom-built kernel. | |
| /var/log/lastlog #last logins | |
| /var/log/messages #the main system log,the messages that are logged during system startup | |
| /var/log/sa/ - Contains the daily sar files that are collected by the sysstat package. | |
| /var/log/samba/ - Contains log information stored by samba, which is used to connect Windows to Linux. | |
| /var/log/setroubleshoot/ - SELinux uses setroubleshootd (SE Trouble Shoot Daemon) to notify about issues in the security context of files and logs those information in this log file. | |
| /var/log/secure #failed login attempts, failed SSH login attempts, successful SSH logins | |
| /var/log/syslog | |
| /var/log/user.log - Contains information about all user level logs. | |
| /var/log/Xorg.x.log - Log messages from the X server to this file. | |
| /var/log/Xorg.0.log | |
| /var/log/yum.log - Contains information that are logged when a package is installed using yum | |
| #binary log files,cannot be read with a normal text editor,special command-line tools are used to display the relevant information in human-readable format | |
| /var/log/btmp - This file contains information about failed login attempts | |
| /var/log/utmp - The utmp file allows one to discover information about who is currently using the system. | |
| /var/log/wtmp - The wtmp file records all logins and logouts. | |
| #This subdirectory contains additional logs from the mail server. | |
| #For example, sendmail stores the collected mail statistics in /var/log/mail/statistics file | |
| /var/log/mail/ | |
| /var/log/maillog - Logs information from the mail server that is running on the system. | |
| /var/log/mail.log - Logs information from the mail server that is running on the system. | |
| #- Contains the apache web server access_log and error_log and related virtual hosts logs if set up to log here. | |
| /var/log/httpd/ | |
| /var/log/apache2 | |
| /var/log/apache2/error.log | |
| /var/log/mysql.log | |
| #All printer and printing related log messages | |
| /var/log/cups | |
| /var/log/spooler | |
| /bin #binaries run during system startup | |
| /sbin #administrative binaries run by superusers | |
| /root #home for superuser | |
| /home #user home dirs | |
| /boot #files run by boot loader and kernel | |
| /dev #peripheral access files | |
| /proc #virtual dir contains system info | |
| /tmp #stores temporary files | |
| /etc/grub.conf or /boot/grub/grub.conf #customize the behavior and appearance of the boot menu | |
| /dev/shm,/dev/shmfs #also known as tmpfs,df -h,file system which keeps all files in virtual memory,no files created on hard drive | |
| /etc/passwd #UID/GID stored, UID/GUID zero(0) for root, all UID/GID <1000 privileged access, all other users UID/GID>1000 | |
| #list group members | |
| /etc/group #secondary group memberships, | |
| awk -F':' '/sudo/{print $4}' /etc/group | |
| grep '^sudo' /etc/group | |
| grep -w sudo /etc/group | |
| ------------------------------------------------------------------------------------------ | |
| "&&" | |
| #where the second command is executed only if the exit status of the preceding command is 0 (zero exit code) | |
| #The right side of && is evaluated if the exit status of the left side is zero (i.e. true) | |
| "||" | |
| #If the exit status of the first command is not 0 (non-zero exit code), then execute the second command | |
| #The right side of || is evaluated if the left side exit status is non-zero (i.e. false) | |
| #Opposite to &&, the statement after the || operator will only be executed if the exit status of the test command is false | |
| [ -f /etc/resolv.conf ] && echo "$FILE exist." || echo "$FILE does not exist." | |
| ------------------------------------------------------------------------------------------ | |
| #Syntax for Command Substitution | |
| #The old-style uses backticks (also called backquotes) to wrap the command being substituted | |
| #The new style begins with a dollar sign and wraps the rest of the command in parenthesis | |
| $ rpm -ql $(rpm -qa | grep httpd) | |
| $(command) #Command Substitution | |
| (list) #Group commands in a subshell: ( ) | |
| { list; } #Group commands in the current shell: { } | |
| [[ expression ]] #Test - return the binary result of an expression: [[ ]] | |
| command substitution; output from pwd works as the argument for echo command | |
| $ echo `pwd` | |
| Command Substitution | |
| # `backquotes` also known as `backticks` | |
| KERNEL_VERSION=`uname -r` | |
| #(parentheses) | |
| KERNEL_VERSION=$( uname -r ) | |
| $ echo $KERNEL_VERSION | |
| 4.15.0-29-generic | |
| #Command substitution in Bash | |
| #execute a command and substitute it with its standard output,command executes within a subshell | |
| $ var_date=$(date) && echo $var_date | |
| $ due_date="01-01" | |
| $ echo "Status as of $(date +%m-%d-%Y) : The delivery is due on ${due_date}-2022" | |
| echo "${myvar:-bash}" #check the variable, $myvar is set or unset. If $myvar is unset, then the string ‘bash’ will print | |
| echo "${myvar:=bash}" #set the value, ‘bash’ to $myvar and print ‘bash’ to the terminal if $myvar is unset | |
| echo "${myvar:+python}" #print, ‘python’ to the terminal if $myvar is set before | |
| $ mystr="Bangladesh" | |
| $ echo "${mystr:0:6}" #six characters from $mystr starting from position 0 to 6 | |
| $ echo "${mystr:6}" #all characters from $mystr, starting from position 6 to the end | |
| $ echo "${#mystr}" #count and print the total number of characters of $mystr | |
| The process substitution >(command) will be replaced by a file name. | |
| ------------------------------------------------------------------------------------------ | |
| { Commands; } : Commands execute in current shell | |
| ( Commands ) : Commands will execute in a subshell | |
| $ VAR="1"; { VAR="2"; echo "Inside group: VAR=$VAR"; }; echo "Outside: VAR=$VAR" | |
| Inside group: VAR=2 | |
| Outside: VAR=2 | |
| #the variable is changed in a subshell. Therefore, the changes will not affect the outer shell | |
| $ VAR="1"; ( VAR="2"; echo "Inside group: VAR=$VAR" ); echo "Outside: VAR=$VAR" | |
| Inside group: VAR=2 | |
| Outside: VAR=1 | |
| $ pwd; { cd /etc; pwd; }; pwd #current shell | |
| $ pwd; ( cd /etc; pwd ); pwd #subshell | |
| ------------------------------------------------------------------------------------------ | |
| #Placing a list of commands between curly braces causes the list to be executed in the current shell context. | |
| #No subshell is created. | |
| $ { ls && v=3; } > tmp | |
| $ echo "$v" | |
| 3 | |
| #pipe creates a new subshell | |
| $ { ls a* && v=3; } | grep my | |
| $ echo "$v" #does not print variable v | |
| touch abc{1,2,3,4} | |
| echo ${month[3]} | |
| echo {10..0} | |
| mkdir /some/dir/{a,b,c,d} | |
| ------------------------------------------------------------------------------------------ | |
| #Parameter Expansion | |
| #specify a variable within {} to protect it against expansion. | |
| #useful when the characters immediately following it can be interpreted as part of the variable name. | |
| $ price=5 | |
| $ echo "${price}USD" | |
| ------------------------------------------------------------------------------------------ | |
| # avoid dot slash "./" when running executable scripts, binary file | |
| #OPTION 1 | |
| export PATH=$PATH:/path/to/directory | |
| #OPTION 2 | |
| ln -s /path_to_script/myscript /usr/bin/myscript | |
| #OPTION 3 | |
| bash -c /Users/you/myscript.sh | |
| #OPTION 4 , add the line below into "~/.bashrc." | |
| export PATH=/path_to_folder_containing_executable/:$PATH | |
| ------------------------------------------------------------------------------------------ | |
| #Hosts File | |
| Windows 10 - "C:\Windows\System32\drivers\etc\hosts" | |
| Linux - "/etc/hosts" | |
| Mac OS X - "/private/etc/hosts" | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #Reading file content from command line | |
| $ while read line; do echo $line; done < company.txt | |
| -------------------------------------------------------------------------------------------------------------------- | |
| mount -t tmpfs tmpfs /mnt/tmp #in-memory filesystem,tmpfs is a temporary filesystem that only exists in RAM | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #which is an external binary, located at /usr/bin/which which steps through the $PATH environment variable and checks for the existence of a file | |
| which modprobe | |
| #command is built in to shell, with the -v option how shell invokes the command specified as its option | |
| command -v modprobe | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #ls -ai command | |
| $ ls .. # double dot(..) represents the parent directory | |
| $ sudo rm .. | |
| rm: cannot remove '..': Is a directory | |
| $ sudo rm -rf .. | |
| rm: refusing to remove '.' or '..' directory: skipping '..' | |
| $ ls . #single dot(.) represents the current directory | |
| $ sudo rm . | |
| rm: cannot remove '.': Is a directory | |
| $ sudo rm -rf . | |
| rm: refusing to remove '.' or '..' directory: skipping '.' | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #list all failed SSH logins | |
| grep "Failed password" /var/log/auth.log | |
| egrep "Failed|Failure" /var/log/auth.log | |
| cat /var/log/auth.log | grep "Failed password" | |
| grep "Failed password" /var/log/auth.log | awk '{print $11}' | uniq -c | sort -nr # the number of failed attempts of each IP address, | |
| -------------------------------------------------------------------------------------------------------------------- | |
| tar -czf - ./Documents/ | (pv -p --timer --rate --bytes > backup.tgz) #Monitor tar progress | |
| pv -p history.log | wc #Count number of lines, words, bytes | |
| pv -p /etc/hosts | wc | |
| pv history.log | zip>$HOME/Documents/history.zip #history.log and show progress | |
| pv origin-cdn.cyberciti.org_access.log > /tmp/origin-cdn-access.log #copy a file and show progress | |
| pv origin-cdn.cyberciti.org_access.log > /dev/null #show progress | |
| pv -cN rawlogfile origin-cdn.cyberciti.org_access.log | gzip | pv -cN gziplogfile > access.log.gz #see progress of both pipes | |
| (pv -n backup.tar.gz | tar xzf - -C path/to/data ) 2>&1 | dialog --gauge "Running tar, please wait..." 10 70 0 #extract tar ball and show progress using the dialog command | |
| tar -czf - ./Documents/ | (pv -n > backup.tgz) 2>&1 | dialog --gauge "Progress" 10 70 | |
| nc -l -v -w 30 -p 2000 > /tmp/data.bin #create a network port 2000 | |
| nc -l -v -w 30 -p 2000 > /tmp/data.bin #Open another terminal | |
| -------------------------------------------------------------------------------------------------------------------- | |
| timeout 10s tail -f /var/log/pacman.log #terminate after 10 seconds | |
| timeout 3.2s dmesg -w #display all messages from the kernel ring buffer, only 3.2 seconds | |
| timeout 3m ping 127.0.0.1 #ping command after 3 minutes | |
| timeout 2d ping 127.0.0.1 #ping command after 2 days | |
| timeout --foreground 2m test.sh #By default runs in background, run it foreground | |
| timeout -k 20 10 tail -f /var/log/pacman.log #if the command is still running even after the time out, send a kill signal | |
| timeout -s 9 3s ping 127.0.0.1 #use 9 as SIGKILL | |
| kill -l #list all acceptable signal | |
| timeout -k 5s 3m sh test.sh #let the script run for 3 minutes, if it does not exit, kill after 5 seconds | |
| -------------------------------------------------------------------------------------------------------------------- | |
| /home/user01/test.file can also be denoted by ~/test.file #The tilde (~) is a Linux "shortcut" to denote a user's home directory. | |
| cd ~ #change into user's home directory | |
| -------------------------------------------------------------------------------------------------------------------- | |
| w #show who is logged on and what they are doing. | |
| w user #print info for a specific user | |
| w -i #display IP address instead of hostname for from field. | |
| w -o #print blank space for idle times less than one minute | |
| -------------------------------------------------------------------------------------------------------------------- | |
| # stops after 50secs, stdout seen | |
| skaffold dev & sleep 50s; kill $! | |
| -------------------------------------------------------------------------------------------------------------------- | |
| $ ssh [email protected] 'bash -s' < script.sh #Execute the local script.sh on the remote server ssh | |
| $ ssh [email protected] 'uptime; df -h' | |
| $ ssh [email protected] 'free -m | cat /proc/loadavg' | |
| $ ssh [email protected] << EOF | |
| uname -a | |
| lscpu | grep "^CPU(s)" | |
| grep -i memtotal /proc/meminfo | |
| EOF | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #setting system locale to en_US.utf8 | |
| localectl set-locale LC_CTYPE=en_US.utf8 | |
| localectl status | |
| ---------------------------------------------------------------------------------------------------- | |
| ip -o -4 addr list enp0s8 | awk '{print $4}' | cut -d/ -f1 # print IP with a given interface | |
| ip -o -6 addr list enp0s8 | awk '{print $4}' | cut -d/ -f1 | |
| ifconfig | awk '/192.168.18.84/ {print $1}' RS="\n\n" # print interface with a given IP | |
| ---------------------------------------------------------------------------------------------------- | |
| #-n do not output the trailing newline | |
| echo -n $PASSWORD | faas-cli login --username admin --password-stdin | |
| ---------------------------------------------------------------------------------------------------- | |
| cat verifyURL.sh | |
| #!/bin/bash | |
| url="https://gist.github.com/githubfoam/d313d580a92d84123b841ebbd4f255a6" | |
| if wget $url >/dev/null 2>&1 ; then | |
| echo "Url : $url ...is online" | |
| else | |
| echo "Url : $url ...is not online" | |
| fi | |
| #if link exists | |
| #--head avoid downloading the file contents | |
| #--fail make the exit status nonzero on a failed request | |
| #--silent avoid status or errors | |
| url="https://www.katacoda.com/courses/kubernetes/launch-single-node-cluster" | |
| if curl --output /dev/null --silent --head --fail "$url"; then | |
| echo "URL exists: $url" | |
| else | |
| echo "URL does not exist: $url" | |
| fi | |
| time curl -I http://mydomain.com | grep HTTP # get the header for the page, and time the process | |
| curl -I "www.google.com" 2>&1 | awk '/HTTP\// {print $2}' # see only the HTTP status code | |
| curl -I "https://www.google.com" 2>&1 | grep -w "200\|301" # see if a given website is up or down | |
| curl -w "\n" http://localhost:8080/hello # avoid your terminal printing a '%' or put both result and next command prompt on the same line | |
| lynx -head -dump http://www.google.com #Check Whether a Website is up or down | |
| lynx -head -dump http://www.google.com 2>&1 | awk '/HTTP\// {print $2}' # see only the HTTP status code | |
| #SSL certificate problem | |
| curl -kfsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg | |
| curl https://curl.se/ca/cacert.pem -o /etc/pki/ca-trust/source/anchors/curl-cacert-updated.pem && update-ca-trust | |
| wget --no-check-certificate http://curl.haxx.se/ca/cacert.pem | |
| ---------------------------------------------------------------------------------------------------- | |
| $ time ./a.out | |
| <output from code> | |
| real 0m5.279s #real is the wall-clock time,Elapsed real time, real time, wall-clock time, or wall time is the actual time taken from the start of a computer program to the end. In other words, it is the difference between the time at which a task finishes and the time at which the task started. | |
| user 0m1.915s #user is the time spent executing the user’s program, | |
| sys 0m0.006s #sys is the time spent on system tasks required by the program | |
| ---------------------------------------------------------------------------------------------------- | |
| #linux benchmark | |
| sysbench --test=cpu run | |
| sysbench --test=cpu help | |
| sysbench --test=cpu --cpu-max-prime=20000 run | |
| sysbench --test=memory run | |
| sysbench --test=memory help | |
| sysbench --test=fileio help | |
| sysbench --test=fileio --file-test-mode=seqwr run | |
| sysbench --test=fileio --file-total-size=100G cleanup | |
| ---------------------------------------------------------------------------------------------------- | |
| # generate load | |
| $ yes > /dev/null & | |
| # maximum number of processes available to a single user. | |
| $ ulimit -u | |
| # The limit is set with the -S option | |
| $ ulimit -S -u 500 | |
| #inspect the load figures on the server before and after the stress test | |
| uptime | |
| sudo stress --cpu 100 --timeout 300 | |
| uptime | |
| $ sudo (yum/apt-get) install stress | |
| ## Stress using CPU-bound task | |
| stress -c 4 | |
| ## Stress using IO-bound task | |
| stress -i 2 | |
| # a load average of four is imposed on the system by specifying two CPU-bound processes, one I/O-bound process, and one memory allocator process | |
| stress -c 2 -i 1 -m 1 --vm-bytes 128M -t 10s | |
| $ sudo apt-get install stress-ng | |
| stress-ng --cpu 4 --io 4 --vm 1 --vm-bytes 1G --timeout 60s --metrics-brief | |
| stress-ng --hdd 5 --hdd-ops 100000 | |
| stress --cpu 4 --io 3 --vm 2 --vm-bytes 256M --timeout 35s | |
| # The restriction can be made permanent by configuring the nproc value | |
| /etc/security/limits.conf | |
| # initiate a fork bomb | |
| ":(){ :|:& };:" | |
| # run ./$0& twice | |
| #!/bin/sh | |
| ./$0& | |
| ./$0& | |
| ---------------------------------------------------------------------------------------------------- | |
| # Listing all currently known events: | |
| perf list | |
| # CPU counter statistics for the specified command: | |
| perf stat command | |
| # CPU counter statistics for the specified PID, until Ctrl-C: | |
| perf stat -p PID | |
| # Sample on-CPU functions for the specified command, at 99 Hertz: | |
| perf record -F 99 command | |
| # Trace all block device (disk I/O) requests with stack traces, until Ctrl-C: | |
| perf record -e block:block_rq_insert -ag | |
| # Add a tracepoint for the kernel tcp_sendmsg() function entry ("--add" is optional): | |
| perf probe --add tcp_sendmsg | |
| # Trace system calls by process, showing a summary refreshing every 2 seconds: | |
| perf top -e raw_syscalls:sys_enter -ns comm | |
| # Show perf.data with a column for sample count: | |
| perf report -n | |
| ---------------------------------------------------------------------------------------------------- | |
| #ls command | |
| ltrace -c ls | |
| ltrace -p <PID> | |
| ltrace -l /lib/libselinux.so.1 id -Z #execute the id -Z command and show the calls made to the libselinux.so module | |
| ltrace -o foobar.log ./foobar #edirect output of ltrace to a file | |
| ltrace -e malloc ./foobar #filter and display only calls to a certain library function | |
| #ls command | |
| strace ls | |
| strace -v #-v verbose option that can provide additional information on each system call | |
| strace -s 80 -f ./program #print the first 80 characters of every string | |
| strace -i ls # print instruction pointer at the time of system call | |
| strace -r ls # display a relative timestamp upon entry to each system call | |
| strace -t ls #each line in strace output to start with clock time | |
| strace -T ls #show time spent in system calls | |
| strace -c ls #print a summary | |
| strace -p 3569 #If a process is already running, you can trace it by simply passing its PID | |
| strace -p `pidof rsyslogd` | |
| strace -p $(pgrep rsyslogd) #monitor process without knowing its PID, but name | |
| #if there are multiple processes to be traced at once (e.g. all instances of an running apache httpd) | |
| strace $( pgrep httpd | sed 's/^/-p/' ) | |
| strace -c -p 3569 Summary of Linux Process | |
| strace -c ls Counting number of sys calls | |
| strace -o output.txt ls | |
| strace -e trace=network -o OUTFILE php -q test2.php # write the output of strace to a file or redirect the output | |
| strace -e trace=network php -q test2.php 2> test2debug #redirect the output | |
| strace -e trace=open,stat,read,write ls | |
| strace -e trace=mprotect,brk ifconfig eth0 # trace mprotect or brk system calls | |
| strace -e trace=network ifconfig eth0 #Trace all the network related system calls | |
| strace -e trace=network #Monitoring the network | |
| strace -e trace=memory Monitoring memory calls | |
| strace -e open ls display only a specific system call, use the strace -e option | |
| strace -f -eopen /usr/sbin/sshd 2>&1 | grep ssh shows the three config files that OpenSSH’s sshd reads as it starts,strace sends its output to STDERR by default | |
| strace -e trace=file -p 1234 #See all file activity,Monitoring file activity | |
| strace -e trace=desc -p 1234 | |
| strace -P /etc/cups -p 2261 #track specific paths, use 1 or more times the -P parameter, following by the path | |
| strace -f -o strace_acroread.txt acroread #follow system calls if a process fork | |
| strace -q -e trace=process df -h trace all system calls involving process management. | |
| strace -q -e trace=file df -h trace all system calls that take a filename as an argument | |
| strace -f -e execve ./script.sh #check what commands are exactly being executed by a script by using strace | |
| strace -f -e execve bash x.sh | |
| $ strace e execve bash -c true | |
| $ strace -ve execve bash -c true | |
| $ strace -e execve bash -c /bin/true | |
| $ strace -o OUT -ff -e execve bash -c "/bin/true ; /bin/false" | |
| $ grep execve OUT* | |
| OUT.29328:execve("/usr/bin/bash", ["bash", "-c", "/bin/true"], 0x7ffc75ace798 /* 25 vars */) = 0 | |
| OUT.29328:execve("/bin/true", ["/bin/true"], 0x55bf673522c0 /* 25 vars */) = 0 | |
| OUT.29336:execve("/usr/bin/bash", ["bash", "-c", "/bin/true ; /bin/false"], 0x7ffe1b316638 /* 25 vars */) = 0 | |
| OUT.29337:execve("/bin/true", ["/bin/true"], 0x55aba17c92c0 /* 25 vars */) = 0 | |
| OUT.29338:execve("/bin/false", ["/bin/false"], 0x55aba17c92c0 /* 25 vars */) = 0 | |
| # Under Linux, fork is a special case of the more general clone system call, which you observed in the strace log. | |
| #The child runs a part of the shell script. The child process is called a subshell. | |
| strace -f -o bash-mystery-1.strace bash -c 'v=15; (echo $v)' | |
| strace -f -o bash-mystery-2.strace bash -c 'v=15; bash x.sh' | |
| man 2 clone #create a child process | |
| grep clone bash-mystery-2.strace # filter child process | |
| strace -e open,read,write cat /etc/HOSTNAME | |
| strace -e open,read,write cat /etc/HOSTNAME > /dev/null | |
| strace -e file cat /etc/HOSTNAME | |
| #Execute Strace on a Running Linux Process Using Option -p | |
| ps -C firefox-bin #PID 126 | |
| sudo strace -p 126 -o firefox_trace.txt #display the following error when your user id does not match the user id of the given process. | |
| pidof sshd #PID 126 | |
| strace -p 126 | |
| #sleep.sh, endless loop | |
| #! /bin/bash | |
| while : | |
| do | |
| sleep 10 & | |
| echo "Sleeping for 4 seconds.." | |
| sleep 4 | |
| done | |
| $ sh sleep.sh & # run in the background | |
| $ pstree -p #see sleep.sh child/parent processes | |
| $ pgrep sleep | sed 's/^/-p/' | |
| $ pidof sleep | |
| $ sudo strace -c -fp PID # attach to parent process of the sleep.sh | |
| $ strace -c -fp $( pgrep sleep | sed 's/^/-p/' ) # another terminal, monitor multipe=le child processes of sleep.sh | |
| $ strace $( pgrep sleep | sed 's/^/-p/' ) # another terminal, monitor multipe=le child processes of sleep.sh | |
| man 3 stat #access the documentation. stat is the system call that gets a file's status | |
| man 2 execve | |
| $ grep openat trace.log | |
| ---------------------------------------------------------------------------------------------------- | |
| PATH=/data/myscripts:$PATH #add directory /data/myscripts to the beginning of the $PATH environment variable | |
| PATH=$PATH:/data/myscripts #add that directory to the end of the path | |
| echo 'export PATH=$PATH:/new/directory' >> ~/.zshrc | |
| source ~/.zshr | |
| ---------------------------------------------------------------------------------------------------- | |
| echo "$(pwd)" | |
| #interpret backslash escapes | |
| echo -e "Tecmint \nis \na \ncommunity \nof \nLinux \nNerds" | |
| echo -e "Tecmint \bis \ba \bcommunity \bof \bLinux \bNerds" | |
| echo -e "Tecmint \tis \ta \tcommunity \tof \tLinux \tNerds" | |
| echo -e "\vTecmint \vis \va \vcommunity \vof \vLinux \vNerds" | |
| echo -e "\n\vTecmint \n\vis \n\va \n\vcommunity \n\vof \n\vLinux \n\vNerds" | |
| echo -e "Geeks \bfor \bGeeks" -e here enables the interpretation of backslash escapes,\b : it removes all the spaces in between the text | |
| echo -e "Geeks \cfor Geeks" \c : suppress trailing new line with backspace interpretor ‘-e‘ to continue without emitting new line. | |
| echo -e "Geeks \nfor \nGeeks" \n : this option creates new line from where it is used. | |
| echo -e "Geeks \tfor \tGeeks" \t : this option is used to create horizontal tab spaces. | |
| echo -e "Geeks \vfor \vGeeks \v : this option is used to create vertical tab spaces. | |
| echo -e "# SNMP version 2c community\nrocommunity monsvronly 192.168.58.8" >> /etc/snmp/snmpd.conf | |
| echo * #print all files/folders, similar to ls command | |
| ---------------------------------------------------------------------------------------------------- | |
| #sh calls the program sh as interpreter and the -c flag means execute the following command as interpreted by this program | |
| #sh -c spawns a non-login, non-interactive session of sh (dash in Ubuntu). | |
| $ sudo sh -c "echo 0" #In Ubuntu, sh is usually symlinked to /bin/dash, meaning that if you execute a command with sh -c the dash shell will be used to execute the command instead of bash | |
| $ readlink -e $(which sh) | |
| /usr/bin/dash | |
| sudo sh -c 'ls -hal /root/ > /root/test.out' #The redirection of the output is performed by sudo. | |
| sudo sh -c "echo foo > ~root/out.txt" | |
| sudo echo "foo" | sudo dd of=/root/test2.out | |
| sudo su -c 'echo "foo" > ~root/test4.out' | |
| sudo su -c 'echo "foobarr" | tee ~root/test5.out' | |
| sudo su -c 'echo "append foobarr " | tee -a ~root/test5.out' | |
| sudo ls /root/out.txt | |
| $ sudo bash -c "echo 0" | |
| $ readlink -e $(which bash) | |
| /usr/bin/bash | |
| #the features that are specific to interactive shells only (by default), e.g. history expansion, source-ing of ~/.bashrc and /etc/bash.bashrc etc will not be available in this session as it is non-interactive | |
| #simulate an interactive sessions behavior (almost), by using the -i option | |
| sh -ic 'ls -hal /root/ > /root/test.out' | |
| #the features that are specific to login shells only (by default) e.g. source-ing of ~/.profile (given ~/.bash_profile and ~/.bash_login do not exist) and /etc/profile will not be done as the shell is a non-login shell | |
| #simulate login-shells behavior using the -l option | |
| sh -lc 'ls -hal /root/ > /root/test.out' | |
| #simulate both login and interactive sessions | |
| sh -lic 'ls -hal /root/ > /root/test.out' | |
| ---------------------------------------------------------------------------------------------------- | |
| brew install <formula> #install a package (or Formula in Homebrew vocabulary) | |
| brew uninstall <formula> | |
| brew upgrade <formula> | |
| brew update | |
| brew list --versions | |
| brew search <formula> | |
| brew info <formula> | |
| brew cleanup --dry-run #see what formulas Homebrew would delete without actually deleting | |
| #Homebrew-Cask extends Homebrew and allows you to install large binary files via a command-line tool | |
| brew tap caskroom/cask #make Cask available by adding it as a tap | |
| #https://brew.sh/ | |
| /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)" #Install Homebrew | |
| ---------------------------------------------------------------------------------------------------- | |
| bash -c "$(curl -sL https://raw.githubusercontent.com/ilikenwf/apt-fast/master/quick-install.sh)" #remote script install | |
| curl https://raw.githubusercontent.com/golang/dep/v0.5.1/install.sh | sh #remote script install | |
| ---------------------------------------------------------------------------------------------------- | |
| ln -s $PWD/istioctl /usr/local/bin/istioctl #create symbolic link | |
| ---------------------------------------------------------------------------------------------------- | |
| hwclock --utc --systohc # set the hardware clock to match system (software) clock on a Linux-only computer, The --utc option tells it to use UTC, which is appropriate for a Linux-only system, --systohc sets the hardware clock based on the current value of the software clock | |
| ---------------------------------------------------------------------------------------------------- | |
| logger shutting down to add network card #create a log file entry noting that you’re manually shutting down the system to add a new network card prior to using shutdown, The logger utility can be used to create a one-time log fle entry that you specify | |
| ---------------------------------------------------------------------------------------------------- | |
| username must contain fewer than 32 characters and start with a letter | |
| may consist of letters, numbers, and certain symbols | |
| ---------------------------------------------------------------------------------------------------- | |
| Deleting a group does not delete all the accounts associated with the group | |
| Groups may have passwords, these are not account login passwords | |
| ---------------------------------------------------------------------------------------------------- | |
| /etc/modprobe.d #all the modules and other files, except for the optional configuration files | |
| stat /lib/modules/`uname -r` #modprobe searches the module directory | |
| more /proc/modules #a text list of the modules that the system has loaded | |
| lsmod #list of currently loaded device drivers | |
| lsmod | wc -l #total loaded Linux kernel modules | |
| lsmod | grep nvidia #see if Linux kernel drivers (modules) named nvidia loaded or not | |
| lsmod | egrep -i 'nvidia|e1000e|kvm_intel' #Search for multiple Linux device driver modules | |
| modinfo e1000 # information about specific driver | |
| ---------------------------------------------------------------------------------------------------- | |
| #KVM | |
| $ egrep -c '(vmx|svm)' /proc/cpuinfo | echo "virtualization is supported" | echo "virtualization is not supported" | |
| $ egrep -c '(vmx|svm)' /proc/cpuinfo && echo "virtualization is supported" || echo "virtualization is not supported" | |
| grep -i vmx /proc/cpuinfo #check if the CPU supports virtualization | |
| lsmod | grep kvm #check if the kvm kernel module is loaded | |
| $ grep -c ^processor /proc/cpuinfo #check that your server has (at least) 8 CPU cores | |
| To run KVM, you need a processor that supports hardware virtualization. | |
| Intel and AMD both have developed extensions for their processors, deemed respectively Intel VT-x (code name Vanderpool) and AMD-V (code name Pacifica) | |
| #If 0 it means that your CPU doesn't support hardware virtualization. | |
| #If 1 or more it does - but you still need to make sure that virtualization is enabled in the BIOS. | |
| $egrep -c '(vmx|svm)' /proc/cpuinfo | |
| $egrep -q 'vmx|svm' /proc/cpuinfo && echo yes || echo no #To use VM drivers, verify that your system has virtualization support enabled | |
| #If the above command outputs “no” | |
| #If you are running within a VM, your hypervisor does not allow nested virtualization. You will need to use the None (bare-metal) driver | |
| #If you are running on a physical machine, ensure that your BIOS has hardware virtualization enabled | |
| $cat /sys/hypervisor/properties/capabilities #if it is enabled or not from xen | |
| $kvm-ok #If you see You can still run virtual machines, but it'll be much slower without the KVM extensions | |
| INFO: Your CPU does not support KVM extensions | |
| KVM acceleration can NOT be used | |
| $egrep -c ' lm ' /proc/cpuinfo #If 0 is printed, it means that your CPU is not 64-bit. If 1 or higher it is 64-bit | |
| $ uname -m | |
| x86_64 | |
| #By default dhcpd based network bridge configured by libvirtd | |
| $ brctl show | |
| $ virsh net-list | |
| #All VMs (guest machine) only have network access to other VMs on the same server. | |
| #A private network 192.168.122.0/24 created | |
| $ virsh net-dumpxml default | |
| virt-install --name=linuxconfig-vm \ | |
| --vcpus=1 \ | |
| --memory=2048 \ | |
| --cdrom=/media/sanchez/KARNAK/linux_distributions/CentOS-Stream-8-x86_64-20210617-dvd1.iso \ | |
| --disk size=5 \ | |
| --os-variant=centos-stream8 | |
| ---------------------------------------------------------------------------------------------------- | |
| wc -mlw file1.txt file2.txt #Count words, characters, and lines in multiple files | |
| ls -l *.pdf | wc -l #Count a Certain Type of Files in a Directory | |
| wc -m yourTextFile # count the total number of characters | |
| wc -w yourTextFile #count the number of words | |
| $ wc -c file1.txt #the number of characters in a file | |
| $ wc -l file1.txt #the number of lines in a file | |
| $ head -5 .bash_history | wc -w # the number of words in the first 5 lines of the file | |
| # filecount=$(ls | wc -l) | |
| # echo $filecount | |
| ---------------------------------------------------------------------------------------------------- | |
| # terminal1 | |
| $ ls > pipe2 | |
| $ mkfifo pipe5 -m700 | |
| $ ls -l > pipe5 | |
| $ rm pipe5 | |
| $rm dir1 #remove a non-empty directory | |
| # terminal2 | |
| $ ls -lart pipe2 # list hidden files in the current directory | |
| prw-rw-r-- 1 vagrant vagrant 0 Feb 25 15:33 pipe2 | |
| $ ls -lart pipe5 | |
| prwx------ 1 vagrant vagrant 0 Feb 25 20:52 pipe5 | |
| $ cat < pipe5 | |
| total 15828 | |
| prw-rw-r-- 1 vagrant vagrant 0 Feb 25 15:33 pipe2 | |
| prw-rw-r-- 1 vagrant vagrant 0 Feb 25 20:51 pipe4 | |
| prwx------ 1 vagrant vagrant 0 Feb 25 20:52 pipe5 | |
| -rw-rw-r-- 1 vagrant vagrant 16207833 Jan 22 22:02 terraform_0.12.20_linux_amd64.zip | |
| ---------------------------------------------------------------------------------------------------- | |
| pushd #stores a directory path in the directory stack,adds directory paths onto a directory stack (history), allows you to navigate back to any directory in history | |
| pushd +2 #use the directory index in the form pushd +# or pushd -# to add directories to the stack and move into | |
| popd #removes the top directory path from the same stack | |
| popd +1 #remove a directory from the directory stack inded use popd +# or popd -# | |
| dirs #display directories in the directory stack (or history) | |
| dirs -v | |
| pushd $(pwd) && cd /opt | |
| popd | |
| ---------------------------------------------------------------------------------------------------- | |
| #from windows to linux copy problem fix | |
| $ make | |
| Makefile:21: *** missing separator. Stop. | |
| $ perl -pi -e 's/^ */\t/' Makefile | |
| # unix/windows file editing | |
| "/bin/bash^M: bad interpreter: No such file or directory" | |
| fix: sed -i -e 's/\r$//' build_all.sh | |
| ---------------------------------------------------------------------------------------------------- | |
| # ls do not provide creation time but change time | |
| $ type ll | |
| ll is aliased to `ls -alF' | |
| # -a option shows all hidden files and directories (Those who start with .") | |
| #the -F classify the results in files and folders,makes it more visual when a lot of files and directories with different extensions exist | |
| ls -alF | |
| ls -i About-TecMint #inode | |
| The Bash shell feature that is used for matching or expanding specific types of patterns is called globbing | |
| $ ls -l ????.txt #files whose names are four characters long | |
| $ ls -l foot????.doc # files whose names are 8 characters long, first 4 characters are f, o, o and t and extension is doc | |
| $ ls -l best.??? #all files with the name ‘test’ having any extension of three characters long | |
| $ ls –lt #lists files in long listing format, and sorts files based on modification time, newest first | |
| $ ls –lth | |
| $ ls –ltr #list down files /folders sorted with modified time, -r reverse order | |
| $ ls -ltr | grep "`date | awk '{print $2" "$3}'`" #todays date | |
| $ ls -ltr | grep "$(date +"%b %e")" | |
| $ ls -ltr | grep "Feb 18" #current date "Mar 22" # list files on specific dates | |
| $ ls -ltr | awk '$6 == "Feb" && $7 >=15 && $7 <= 31 {print $6,$7,$8,$9}' # list files after Feb 15t | |
| $ ls -ltr . | awk '$6 == "Feb" && $7 >=15 && $7 <= 31 {print $6,$7,$8,$9}' # list files after Feb 15t on specific directory | |
| $ ls -lrt /var/log | awk '{ total += $5 }; END { print total }' # sum of file sizes | |
| $ ls -FaGl /var/log/apt | printf "%'d\n" $(awk '{SUM+=$4}END{print SUM}') #total size | |
| $ ls -FaGl /var/log/apt | sudo tee /dev/stderr | printf "%'d\n" $(awk '{SUM+=$4}END{print SUM}') #list directory contents and total size | |
| $ ls -laUR /var/log/apt | grep -e "^\-" | tr -s " " | cut -d " " -f5 | awk '{sum+=$1} END {print sum}' #only sum up file sizes not the directory itself | |
| # total size, sum of files listed | |
| $ sumcol() | |
| > { | |
| > awk "{sum+=\$$1} END {print sum}" | |
| > } | |
| $ ls -lrt /var/log/apt/ | sumcol 5 | |
| $ ls -l | grep 'Mar 22 12:27' | tr -s ' ' | cut -d ' ' -f9 | xargs rm -rf #delete files on specific date | |
| #Listing of files in directory based on last modification time of file’s status information, or the 'ctime' | |
| #list that file first whose any status information like: owner, group, permissions, size etc has been recently changed. | |
| $ ls –lct #List Files Based on Last Modification Time | |
| $ ls –ltu #Listing of files in directory based on last access time, i.e. based on time the file was last accessed, not modified. | |
| #Sorting Ouptut of ls -l based on Date | |
| #based on 6th field month wise, then based on 7th field which is date, numerically | |
| ls -l | sort -k6M -k7n | |
| ls -l | head -n 10 | sort -k6 | |
| ls -l | head -n 10| sort -k6M -k7n #based on 6th field month wise, then based on 7th field which is date | |
| ls -lt --time=birth #sorted by creation/birth date time | |
| ls -l --time=creation #sorted by creation/birth date time | |
| $ ls -l *.pl #all files of ‘pl’ extension | |
| $ ls -l [p-s]* #all files and folders whose name contains p or q or r or s | |
| $ ls -l [1-5]* #all files and folders whose name starts with any digit from 1 to 5 | |
| $ ls -l {?????.sh,*st.txt} #files whose names are 5 characters long and the extension is ‘sh’ or the last two characters of the files are ‘st’ and the extension is ‘txt’ | |
| $ rm {*.doc,*.docx} #delete all files whose extensions are ‘doc’ or ‘docx’ | |
| $ ls a*+(.bash|.sh) #filenames which are starting with character ‘a’ and has the extension ‘bash’ or ‘sh’ | |
| ls -alt #list files in last modifed date order use the -t flag which is for 'time last modified'. | |
| ls -altr #list files in last modifed date order use the -t flag which is for 'time last modified', reverse order | |
| ---------------------------------------------------------------------------------------------------- | |
| echo test > >(cat) #the output of echo would be redirected to the file that serves as the input to cat, and cat would produce the contents of that file on standard output | |
| echo foo | cat -n | |
| echo foo > >(cat -n) # emulate pipe above | |
| The process substitution >(command) will be replaced by a file name. | |
| This file name corresponds to a file that is connected to the standard input of the "command" inside the substitution | |
| $ cat .profile | while read line; do ((counter1++)); done | |
| $ echo $counter1 | |
| $ while read line; do ((count++)); done < <(cat ~/.profile) | |
| $ echo $count | |
| 101 | |
| ---------------------------------------------------------------------------------------------------- | |
| #Network Troubleshooting | |
| Step 1: Check if your interface is configured | |
| $ ifconfig | |
| sudo resolvconf -u | |
| Step 2: Setting up your interface | |
| check if the drivers are loaded | |
| $ dmesg | grep -3 -i eth | |
| configure the interface | |
| ifconfig eth0 128.42.14.176 netmask 255.255.255.0 up | |
| Assign a Broadcast to Network Interface | |
| ifconfig eth0 netmask 255.255.255.224 | |
| If the loopback interface is not up | |
| ifconfig lo up | |
| now be able to ping your own machine | |
| $ ping -c 3 127.0.0.1 | |
| Step 3: Check if you can ping the gateway | |
| ping the DNS server | |
| Step 6: Setting up routing | |
| # route add -net <naddr> netmask <maddr> eth0 | |
| # route add default gw <gaddr> eth0 | |
| setup the loopback route if it's missing | |
| # route add -host 127.0.0.1 lo | |
| #Adding and removing routes | |
| ip ro add 10.0.0.0/16 via 192.0.2.253 | |
| ip ro del 10.0.0.0/16 via 192.0.2.253 | |
| ip ro | |
| ip -6 ro #IPv6 | |
| ip route get 8.8.8.8 | sed -n '/src/{s/.*src *\([^ ]*\).*/\1/p;q}' # IP reaching the public internet, multiple IPs interfaces | |
| ip ro get $dst_ip from $src_ip #Check routing path | |
| ip ro get 192.0.0.0 | |
| $ ip route show | |
| default via 10.0.2.2 dev eth0 proto dhcp metric 100 | |
| 10.0.2.0/24 dev eth0 proto kernel scope link src 10.0.2.15 metric 100 | |
| 192.168.18.0/24 dev eth1 proto kernel scope link src 192.168.18.9 metric 101 | |
| traffic to anywhere else should be forwarded through eth0 to the gateway at 10.0.2.2 | |
| traffic to 10.0.2.2 (the gateway to the public Internet) should be forwarded directly to its destination through eth0 | |
| traffic to anywhere within 192.168.18.0/24 (the local area network) should be forwarded directly to its destination through eth1 | |
| $ ip route get to 192.168.18.12 from 192.168.18.9 iif eth1 | |
| $ ip route get to 192.168.18.9 from 192.168.18.12 iif eth1 | |
| $ route -n | |
| route add dest_ip_address gateway_address #Add a route to a destination through a gateway | |
| route add subnet_ip_address/24 gateway_address #Add a route to a /24 subnet through a gateway | |
| route -t add dest_ip_address/24 gateway_address #Run in test mode (does not do anything, just print) | |
| route flush #Remove all routes | |
| route delete dest_ip_address/24 #Delete a specific route | |
| Step 7: Name resolution | |
| 3 files: /etc/host.conf, /etc/hosts, /etc/resolv.conf | |
| /etc/host.conf: | |
| order hosts,bind | |
| multi on | |
| /etc/hosts: | |
| 127.0.0.1 localhost loopback | |
| <IPaddr> this.host.name | |
| /etc/resolv.conf: | |
| domain yourdept.yourcompany.com | |
| search yourdept.yourcompany.com yourcompany.com | |
| nameserver <domainaddr> | |
| ---------------------------------------------------------------------------------------------------- | |
| # ping a host | |
| ping 192.168.0.2 | |
| #show routing table without resolving domain names | |
| netstat -nr | |
| netstat -r -n # The flag U indicates that route is up and G indicates that it is gateway | |
| netstat -alun | grep 161 | |
| # show informations about errors/collisions | |
| netstat -ni | |
| # show statistics about your network card | |
| netstat -i -I em0 | |
| netstat -a | |
| netstat -at | |
| netstat -s | |
| netstat -au | |
| netstat -l | |
| netstat -lu | |
| netstat -lt | |
| netstat -tulpn | |
| netstat -plan | |
| netstat -plan | grep ":80" | |
| netstat -lntp | grep ':8080.*java' > /dev/null && command | |
| netstat -pan -A inet,inet6 | grep -v ESTABLISHED #determine which ports are listening for connections from the network | |
| netstat -tlnw #Use the -l option of the netstat command to display only listening server sockets: | |
| netstat -plnS #Scan for Open SCTP Ports | |
| netstat -nl -A inet,inet6 | grep 2500 #Scan for Open SCTP Ports | |
| netstat -pant | grep -Ei 'apache|:80|:443' | |
| netstat -tunlp | grep ":80 " | |
| List all TCP sockets and related PIDs | |
| netstat -antp | |
| netstat -anp | |
| List all UDP sockets and related PIDs | |
| netstat -anup | |
| # find out on which port a program is running | |
| netstat -ap | grep ssh | |
| #If there is an IP address instead, then the port is open only on that specific interface | |
| #For listening ports, if the source address is 0.0.0.0, it is listening on all available interfaces | |
| #The Recv-Q and Send-Q fields show the number of bytes pending acknowledgment in either direction | |
| #the PID/Program name field shows the process ID and the name of the process responsible for the listening port or connection | |
| netstat -anptu | |
| #number of established connection | |
| netstat -an|grep ESTABLISHED|awk '{print $5}'|awk -F: '{print $1}'|sort|uniq -c|awk '{ printf("%s\t%s\t",$2,$1); for (i = 0; i < $1; i++) {printf("*")}; print ""}' | |
| #see that the Nessus server is up and running | |
| netstat -n | grep tcp | |
| netstat -tap | grep LISTEN | |
| netstat -pltn | grep 8834 | |
| ---------------------------------------------------------------------------------------------------- | |
| #ss is the socket statistics command that replaces netstat | |
| ss -tr #netstat -t | |
| ss -ntr #see port numbers | |
| ss -an |grep LISTEN #netstat -an |grep LISTEN | |
| ss -an | grep 2500 #show SCTP open ports | |
| ss -tlw # list open ports in the listening state | |
| ss -plno -A tcp,udp,sctp #The UNCONN state shows the ports in UDP listening mode | |
| ---------------------------------------------------------------------------------------------------- | |
| # find route to example.com | |
| traceroute www.example.com | |
| #find route to example.com using tcptraceroute (which uses tcp to discover path) | |
| tcpdraceroute www.example.com | |
| # The maximum number of hops can be adjusted with the -m flag. | |
| traceroute -m 255 obiwan.scrye.net | |
| # adjust the size of the packet that is sent to each hop by giving the integer after the hostname | |
| traceroute google.com 70 | |
| Specify Gateway | |
| sudo traceroute -g 10.0.2.2 yahoo.com | |
| traceroute -g 192.5.146.4 -g 10.3.0.5 35.0.0.0 | |
| #shows the path of a packet that goes from istanbul to sanfrancisco through the hosts cairo and paris | |
| #The -I option makes traceroute send ICMP ECHO probes to the host sanfrancisco | |
| #The -i options sets the source address to the IP address configured on the interface qe0 | |
| traceroute -g cairo -g paris -i qe0 -q 1 -I sanfrancisco | |
| ip r / ip route #gateway / router | |
| ip r | grep default #default gateway | |
| route -n # The flag U indicates that route is up and G indicates that it is gateway | |
| route -nee | |
| netstat -r -n # The flag U indicates that route is up and G indicates that it is gateway | |
| routel #list routes | |
| routel | grep default #default gateway | |
| Specify Source Interface | |
| sudo traceroute -i eth0 yahoo.com | |
| Autonomous Systems | |
| traceroute -A yahoo.com | |
| tracepath yahoo.com | |
| tracepath -n yahoo.com | |
| tracepath -b yahoo.com | |
| sets the initial packet length | |
| tracepath -l 28 yahoo.com | |
| set maximum hops (or maximum TTLs) to max_hops | |
| tracepath -m 5 yahoo.com | |
| set the initial destination port to use | |
| tracepath -p 8081 yahoo.com | |
| hostname -f #show fully qualified domain name (FQDN) | |
| hostname #shortname | |
| hostname -I #the primary/first IP address | |
| hostname -I | awk '{print $1}' # get primary/first IP IP address of server | |
| hostname -I | awk '{print $2}' # get second IP IP address of server | |
| real-time view of the current state of your system | |
| $ htop | |
| $ timedatectl | |
| $ timedatectl list-timezones | |
| $ sudo timedatectl set-timezone 'Africa/Lubumbashi' | |
| # Enable NTP synchronization | |
| timedatectl set-ntp true | |
| timedatectl status | |
| # show connected sockets | |
| sockstat -c | |
| # show listening sockets and processes | |
| sockstat -l | |
| # show arp table | |
| arp -a #Show current arp tabl | |
| arp -na | |
| ip neighbour #Show neighbors (ARP table) | |
| arp -d 192.168.0.2 # delete a record from arp table | |
| sudo arp -a -d #Clear the entire cach | |
| arp -s 192.168.0.2 00:10:b5:99:bf:c4 #add a static record in arp table | |
| # listen on em0 network interface and sniff packets that pass via em0 | |
| $ sudo arp -i eth0 | |
| find out reachability of an IP on the local Ethernet with arping i.e send ARP request 192.168.1.1: | |
| $ sudo arping -I eth0 -c 3 192.168.18.12 | |
| $ sudo arping -I eth1 -c 3 192.168.18.12 | |
| Find duplicate IP | |
| $ sudo arping -D -I eth1 -c 3 192.168.18.12 | |
| ping -I eth0 8.8.8.8 #ping 8.8.8.8 using eth0 as a source interface | |
| ping google.com | |
| ping -6 hostname/IPv6 #request IPv6 or IPv4 address | |
| ping -4 hostname/IPv4 | |
| #The default interval between each ping request is set to one second. You can increase or decrease that time using the –i switch | |
| #decrease the ping interval, use values lower than 1 | |
| ping -i 0.5 google.com | |
| ping -s 1000 google.com #use -s to increase the packet size from the default value of 56 (84) bytes. | |
| ping -f hostname-IP #use ping flood to test your network performance under heavy load | |
| ping -c 2 google.com #Limit Number of Ping Packets | |
| ping -w 25 google.com #stop printing ping results after 25 seconds | |
| ping -c 10 -q google.com #The letter “q” in this command stands for “quiet” output. | |
| ping -D google.com #Add Timestamp Before Each Line in ping Output | |
| $ file * | |
| 20:30: empty | |
| file1: ASCII text | |
| file2: ASCII text | |
| $ file raw_file.txt #if a text file contains ASCII or Unicode | |
| $ file -b symbolic_test1.txt | |
| symbolic link to test1.txt | |
| ----------------------------------------------------------------------------------------------------- | |
| # parse html with curl | |
| curl -s https://miloserdov.org/ | grep -E -o '<h3 class=ftitle>.*</h3>' | sed 's/<h3 class=ftitle>//' | sed 's/<\/h3>//' | |
| curl http://test.com | sed -rn 's@(^.*<dd>)(.*)(</dd>)@\2@p' | |
| cat - > file.html << EOF | |
| <div class="tracklistInfo"> | |
| <p class="artist">Diplo - Justin Bieber - Skrillex</p> | |
| <p>Where Are U Now</p> | |
| </div><div class="tracklistInfo"> | |
| <p class="artist">toto</p> | |
| <p>tata</p> | |
| </div> | |
| EOF | |
| cat file.html | tr -d '\n' | sed -e "s/<\/div>/<\/div>\n/g" | sed -n 's/^.*class="artist">\([^<]*\)<\/p> *<p>\([^<]*\)<.*$/artist : \1\ntitle : \2\n/p' | |
| cat file.html | grep -A2 -E -m 1 '<div class="tracklistInfo">' | |
| cat file.html | grep -A2 -E -m 1 '<div class="tracklistInfo">' | tail -n1 | |
| cat file.html | grep -A2 -E -m 1 '<div class="tracklistInfo">' | tail -n2 | head -n1 | |
| cat file.html | grep -A2 -E -m 1 '<div class="tracklistInfo">' | tail -n2 | head -n1 | sed 's/<[^>]*>//g' | |
| ----------------------------------------------------------------------------------------------------- | |
| Check what ethernet devices exist currently | |
| # ls -al /sys/class/net | |
| # ls -Rl | |
| list hidden files and the contents of all subdirectories | |
| ls -aR /home/username | |
| # ls -pu | |
| see eth* devices | |
| # ls -al /sys/class/net | |
| Get the PCI address of the NIC | |
| # lspci | grep Mellanox | |
| # lspci | grep Eth | |
| iw distinguishes between wireless LAN hardware devices (the physical layer, referred to as phy) and the network interface configured to use that hardware (e.g. wlan0, | |
| similar to an Ethernet eth0 interface). To see the list of devices, and interfaces for each device | |
| #iw dev | |
| **MAC_ADDRESS 08:00:27:e3:b0:01 | |
| $ ip link show eth1 | |
| 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000 | |
| link/ether 08:00:27:e3:b0:01 brd ff:ff:ff:ff:ff:ff | |
| $ ip addr show eth1 | |
| 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 | |
| link/ether 08:00:27:e3:b0:01 brd ff:ff:ff:ff:ff:ff | |
| inet 192.168.1.253/24 brd 192.168.1.255 scope global noprefixroute eth1 | |
| valid_lft forever preferred_lft forever | |
| inet6 fe80::a00:27ff:fee3:b001/64 scope link | |
| valid_lft forever preferred_lft forever | |
| #temporarily set the IP address | |
| ifconfig eth0 192.168.8.185 | |
| ifconfig eth0 192.168.8.185 netmask 255.255.255.0 up | |
| #temporarily change the MAC address | |
| ifconfig eth0 down hw ether AA:BB:CC:DD:EE:FF && ifconfig eth0 up | |
| ifconfig eth0 netmask 255.255.255.0 | |
| ifconfig eth0 broadcast 192.168.70.255 | |
| ip addr show -> List IP address of the server | |
| ip addr show eth0 | |
| ip addr | grep inet6 #check that your server supports IPV6 | |
| ip addr show eth1 | grep "inet " | |
| ip addr add 10.132.1.1/24 dev eth1 -> Add a new IP4 address | |
| ip addr show eth1 -> confrm that the new address is available on the interface | |
| ip link set eth2 down -> bring an interface down | |
| ip link set eth2 up | |
| ip -s link->view basic network statistics on all interfaces | |
| ip -s link ls eth0 ->see the statistics for the eth0 interface | |
| ip -s -s link ls eth0 ->see additional info | |
| ss -t ->show established TCP connections | |
| ss -u ->show established UDP connections | |
| ss -A tcp | |
| ss -x | |
| ss -ltn ->see which ports are listening for connections | |
| ss -nt | |
| ss -ltn | |
| ss -ua | |
| ss -a -A udp | |
| ss -lun ->udp | |
| ss -s->prints out the statistics | |
| #Install sysstat package | |
| # /etc/default/sysstat ENABLED="true" | |
| #sudo service sysstat restar | |
| vmstat 1 99999 ->the system statistics every second, for the number of times specifed (99999 in this instance) | |
| vmstat –a 1 99 ->show memory usage information | |
| vmstat -a -S M 1 9 -> reformat in Mega Bytes | |
| vmstat 1 99999 ->gather information for disks and other block devices | |
| vmstat -d -w | |
| iostat 1 9 ->CPU information and disk information for all devices | |
| iostat -d -p sda 1 9-> show information for device sda with disk statistics | |
| sar -u 1 30 -> display CPU statistics every second for 30 seconds | |
| sar -r 1 30 -> display memoru statistics every second for 30 seconds | |
| sar -b 1 30 -> display block device statistics every second for 30 seconds | |
| #===================================================================== | |
| # curl the binay version info from latest download and later wget the file with | |
| $curl -s https://api.github.com/repos/prometheus/prometheus/releases/latest \ | |
| | grep browser_download_url \ | |
| | grep linux-amd64 \ | |
| | cut -d '"' -f 4 \ | |
| | wget -qi - | |
| $ ls | |
| prometheus-2.37.0.linux-amd64.tar.gz | |
| $tar xvf prometheus*.tar.gz | |
| $cd prometheus*/ | |
| #specify directory and rename the file | |
| wget --output-document="/home/my_new_file_name" http://someurl | |
| #add the appropriate BeeGFS repositories | |
| wget -o /etc/yum.repos.d/beegfs-rhel7.repo http://www.beegfs.com/release/beegfs_2015.03/dists/beegfs-rhel7.repo | |
| wget -q https://www.virtualbox.org/download/oracle_vbox.asc -O- | apt-key add - | |
| wget example.com/big.file.iso #start download and stop download ctrl+c key pair | |
| wget -c example.com/big.file.iso #resume download | |
| wget ‐‐continue example.com/big.file.iso #Resume an interrupted download previously started by wget itself | |
| wget ‐‐continue ‐‐timestamping wordpress.org/latest.zip #Download a file but only if the version on server is newer than your local copy | |
| wget ‐‐page-requisites ‐‐span-hosts ‐‐convert-links ‐‐adjust-extension http://example.com/dir/file #Download a web page with all assets - like stylesheets and inline images - that are required to properly display the web page offline. | |
| wget -q http://somesite.com/TheFile.jpeg #-q: Turn off wget's output | |
| wget http://example.com/images/{1..20}.jpg # Download a list of sequentially numbered files from a server | |
| wget -m -r -linf -k -p -q -E -e robots=off http://127.0.0.1 # Download a complete website | |
| wget ‐‐mirror ‐‐domains=abc.com,files.abc.com,docs.abc.com ‐‐accept=pdf http://abc.com/ #Download the PDF documents from a website through recursion but stay within specific domains. | |
| wget ‐‐execute robots=off ‐‐recursive ‐‐no-parent ‐‐continue ‐‐no-clobber http://example.com/ #Download an entire website including all the linked pages and files | |
| wget ‐‐level=1 ‐‐recursive ‐‐no-parent ‐‐accept mp3,MP3 http://example.com/mp3/ #Download all the MP3 files from a sub-directory | |
| wget --recursive --no-clobber --page-requisites --html-extension --convert-links --restrict-file-names=windows --domains some-site.com --no-parent www.some-site.com #Download Entire Website | |
| wget ‐‐recursive ‐‐no-clobber ‐‐no-parent ‐‐exclude-directories /forums,/support http://example.com #Download all files from a website but exclude a few directories | |
| wget --reject=png www.some-site.com #Reject file types while downloading | |
| wget -r -A .pdf http://some-site.com/ #Download all PDF files from a website | |
| wget -r -H --convert-links --level=NUMBER --user-agent=AGENT URL #Download With Wget Recursively,declare a user agent such as Mozilla (wget –user-agent=AGENT) | |
| wget -e https_proxy=xx.xx.xx.xx:8080 https://example.com/ #use proxy server with wget | |
| wget -S --spider http://www.uniqlo.com/ #Only Header Information | |
| ##if link exists | |
| url="https://www.katacoda.com/courses/kubernetes/launch-single-node-cluster" | |
| if wget --spider "$url" 2>/dev/null; then #2> /dev/null silences wget's stderr output | |
| echo "URL exists: $url" | |
| else | |
| echo echo "URL does not exist: $url" | |
| fi | |
| #connect to a remote server,start download on the remote server,disconnect from the remote server,let it run on the background | |
| $ nohup wget -q url & | |
| wget -i file.txt #Read download URLs from a file,useful in a shell script. | |
| #one liner if condition | |
| wget --spider http://192.168.50.15/${distribution}_${codename}_oscap_report.html 2>/dev/null && echo "link exists" || echo "link does not exist" | |
| wget --spider -S "www.magesh.co.in" 2>&1 | awk '/HTTP\// {print $2}' #see only the HTTP status code | |
| wget --spider -o wget.log -e robots=off --wait 1 -r -p http://www.mysite.com/ #crawl a website and generate a log file of any broken links | |
| wget --spider https://example.com/filename.zip 2>&1 | grep Length #file download size without downloading the actual file | |
| wget ‐‐spider ‐‐server-response http://example.com/file.iso #Find the size of a file without downloading it (look for ContentLength in the response, the size is in bytes) | |
| wget ‐‐output-document - ‐‐quiet google.com/humans.txt #Download a file and display the content on the screen without saving it locally | |
| wget ‐‐server-response ‐‐spider http://www.labnol.org/ #the last modified date of a web page (check the LastModified tag in the HTTP header) | |
| wget ‐‐output-file=logfile.txt ‐‐recursive ‐‐spider http://example.com #Check the links on your website to ensure that they are working. The spider option will not save the pages locally. | |
| wget ‐‐limit-rate=20k ‐‐wait=60 ‐‐random-wait ‐‐mirror example.com # limited the download bandwidth rate to 20 KB/s and the wget utility will wait anywhere between 30s and 90 seconds before retrieving the next resource. | |
| wget -O index.html --certificate=OK.crt --private-key=OK.key https://example.com/ #Client SSL Certificate | |
| wget -q -O - --header="Content-Type:application/json" --post-file=foo.json http://127.0.0.1 # POST a JSON file and redirect output to stdout | |
| wget -O wget.zip http://ftp.gnu.org/gnu/wget/wget-1.15.tar.gz #Download file with different name | |
| wget -o download.log http://ftp.gnu.org/gnu/wget/wget-1.15.tar.gz #redirect the wget command logs to a log file using ‘-o‘ switch. | |
| wget ‐‐output-document=filename.html example.com #Download a file but save it locally under a different name | |
| wget ‐‐directory-prefix=folder/subfolder example.com #Download a file and save it in a specific folder | |
| wget -r -l inf -A .png,.jpg,.jpeg,.gif -nd https://jekyllrb.com # Download all images of a website | |
| wget -r --level=1 -H --timeout=1 -nd -N -np --accept=mp3 -e robots=off -i musicblogs.txt #take a text file of your favourite music blogs and download any new MP3 files | |
| wget --ftp-user=User --ftp-password=Mir URL # FTP download | |
| wget http://ftp.gnu.org/gnu/wget/wget-1.15.tar.gz ftp://ftp.gnu.org/gnu/wget/wget-1.14.tar.gz.sig #Download multiple file with http and ftp protocol | |
| wget -i /wget/urls.txt #Read URL’s from a file | |
| wget -Q10m -i download-list.txt #Setting Download Quota | |
| wget -c http://ftp.gnu.org/gnu/wget/wget-1.15.tar.gz #Resume download | |
| wget -b /wget/log.txt http://ftp.gnu.org/gnu/wget/wget-1.15.tar.gz #Download files in background | |
| wget -b -c --tries=NUMBER URL #number of tries (wget –tries=NUMBER), continue partial download (wget -c) | |
| wget -b --limit-rate=SPEED -np -N -m -nd --accept=mp3 --wait=SECONDS http://www.uniqlo.com/ #no parent to ensure you only download a sub-directory (wget -np),update only changed files (wget -N), mirror a site (wget -m), ensure no new directories are created (wget -nd), accept only certain extensions (wget –accept=LIST) | |
| wget -c --limit-rate=100k /wget/log.txt http://ftp.gnu.org/gnu/wget/wget-1.15.tar.gz #Limit download speed | |
| wget --http-user=username --http-password=password http://some-network.net/some-file.txt #Options –http-user=username, –http-password=password | |
| wget --ftp-user=username --ftp-password=password ftp://some-network.net/some-file.txt #–ftp-user=username, –ftp-password=password | |
| wget --tries=75 http://ftp.gnu.org/gnu/wget/wget-1.15.tar.gz #Increase Retry Attempts. | |
| wget ‐‐refer=http://google.com ‐‐user-agent="Mozilla/5.0 Firefox/4.0.1" http://nytimes.com #Wget can be used for downloading content from sites that are behind a login screen or ones that check for the HTTP referer and the User-Agent strings of the bot to prevent screen scraping. | |
| wget ‐‐cookies=on ‐‐save-cookies cookies.txt ‐‐keep-session-cookies ‐‐post-data 'user=labnol&password=123' http://example.com/login.php_ _wget ‐‐cookies=on ‐‐load-cookies cookies.txt ‐‐keep-session-cookies http://example.com/paywall #Fetch pages that are behind a login page. You need to replace user and password with the actual form fields while the URL should point to the Form Submit (action) page. | |
| wget ‐‐span-hosts ‐‐level=inf ‐‐recursive dmoz.org # | |
| wget -r --level=inf -p -k -E --span-hosts --domains=domainA,domainB http://www.domainA #download an entire site (domain A) when its resources are on another domain, (domain B) | |
| wget --page-requisites --convert-links --adjust-extension --span-hosts --domains domainA,domainB domainA # | |
| wget --recursive --level=inf --page-requisites --convert-links --html-extension -rH -DdomainA,domainB domainA # | |
| wget --recursive --level=inf --page-requisites --convert-links --adjust-extension --span-hosts --domains=domainA,domainB domainA # | |
| #===================================================================== | |
| sudo permission denied | |
| The redirection to a file is handled by bash. It does therefore not inherit permissions granted by sudo. | |
| "sudo tee" for writing to a file as root. | |
| lsblk -f -> when used with the -f option, it prints file system type on partitions | |
| sudo file -sL /dev/sdb1 -> file system type on partitions | |
| lsblk -f | |
| lsblk -l | |
| lsblk --scsi | |
| lsblk -o name,type,fstype,label,partlabel,model,mountpoint,size | |
| #/etc/fstab explained, Each field can be separated by another either by spaces or tabs | |
| First field – The block device,reference a block device is by using its LABEL or UUID (Universal Unique IDentifier) | |
| $ lsblk -d -fs /dev/sdb1 # get UUID | |
| Second field – The mountpoint | |
| Third field – The filesystem type | |
| Fourth field – Mount options, use the default set of mount options we specify default as a value | |
| Fifth field – Should the filesystem be dumped?, either 0 or 1,used by the dump backup program (if installed) | |
| Sixth field – Fsck order;fsck utility, should check filesystems on boot; | |
| value of 1 must always be used for the root filesystem | |
| if not root filesystem,for all the others, value of 2 | |
| If not provided it defaults to 0 | |
| # generate traces of the i/o traffic on block devices | |
| "sudo blktrace -d /dev/sda -o - | blkparse -i -" | |
| #writing ISO usb bootable | |
| sudo umount /dev/sdX | |
| sudo dd if=/path/to/ubuntu.iso of=/dev/sdX bs=4M && sync | |
| sdx-> lslbk command | |
| sync-> sync bit is important as dd can return before the write operation finishes. | |
| # mount all file systems on /etc/fstab | |
| mount -a | |
| mount -fav | |
| cat /proc/mounts | |
| # format linux swap partition | |
| mkswap | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #search man pages | |
| man -K date -> display a list of all manual pages containing the keyword "date" | |
| man -wK word ->list out all manual files with some word. | |
| $ man yum | less +/"install @" #search "install @" pattern in man yum page | |
| $ man -P 'less -p install ' yum #search "install" pattern in man yum page | |
| -------------------------------------------------------------------------------------------------------------------- | |
| # Clone / Compile specific kernel | |
| sudo git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git linux -> latest stable kernel to "linux" directory | |
| git tag -l | grep v4.9.1 -> find specific kernel version | |
| git checkout -b kernel490 v4.9.1 -> switch to kernel with custom name "kernel490" | |
| #tail -f vs less +F | |
| #tail -f only reads the end of the file | |
| #tail -f doesn't keep the whole file in memory. | |
| tail -f /var/log/syslog | |
| #less +F reads the whole file | |
| #less +F impractical for very large files. | |
| #less +F can highlight, search, navigate through file | |
| #hit Ctrl-c to go to “normal” less mode (as if you had opened the file without the +F flag) | |
| #the search with /foo,next or previous occurrence with n or N, up and down with j and k,, create marks with m | |
| #hit F to go back to watching mode | |
| less +F /var/log/syslog | |
| less -n +F #read only the end of the file | |
| tail -100f /var/log/messages | grep -V ACPI | grep -i ata #real-time monitoring,tailing 100 lines from the end | |
| tail -f /var/log/nginx/access.log /var/log/nginx/access.log #watching multiple files | |
| multitail /var/log/auth.log /var/log/kern.log #shows the contents of log files horizontally | |
| multitail -s 2 /var/log/auth.log /var/log/kern.log #view the contents of log files vertically in two columns | |
| multitail -s 2 /var/log/syslog, /var/log/kern.log, /var/log/daemon.log and var/log/messages | |
| multitail -s 2 -ci green /var/log/auth.log -ci blue /var/log/kern.log | |
| lnav /var/log/syslog /var/log/messages | |
| lnav a.zip b.zip | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #crontab | |
| Display scheduled jobs for the specified user | |
| crontab -l -u vagrant | |
| crontab -l | |
| # Display Cron Table | |
| ls -la /etc/cron* | |
| sudo crontab -u user -e # | |
| crontab -e #when running as a non-root user | |
| sudo crontab -e #the root user's crontab | |
| #If the /etc/cron.allow file exists, then users must be listed in it in order to be allowed to run the crontab command | |
| #If the /etc/cron.allow file does not exist but the /etc/cron.deny file does, | |
| #then users must not be listed in the /etc/cron.deny file in order to run crontab | |
| #If the /etc/cron.allow file exists, then users must be listed in it in order to be allowed to run the crontab command | |
| /etc/cron.deny # If a blank cron.deny file has been created, cron only available to root or users in cron.allow. | |
| # Delete All Cron Jobs | |
| crontab -r | |
| crontab -r -i #the command prompt to confirm | |
| # All scripts in each directory are run as root | |
| #Cron jobs may not run with the environment, in particular the PATH, that you expect. Try using full paths to files and programs | |
| #The "%" character is used as newline delimiter in cron commands. If you need to pass that character into a script, you need to escape it as "\%". | |
| #anacron uses the run‑parts command and /etc/cron.hourly, /etc/cron.weekly, and /etc/cron.monthly directories. | |
| #anacron itself is invoked from the /etc/crontab file | |
| #user crontabs | |
| /etc/cron.hourly/, /etc/cron.daily/, /etc/cron.weekly/, and /etc/cron.monthly/ | |
| ls -la /etc/cron.daily/ #View daily cron jobs | |
| crontab -l > backup_cron.txt #Backup All Cron Jobs | |
| /etc/crontab #not recommended that you add anything,this could cause a problem if the /etc/crontab file is affected by updates | |
| /etc/cron.d #not be affected by updates, several people might look after a server, then the directory /etc/cron.d is probably the best place to install crontabs | |
| /etc/cron.d #These files also have username fields | |
| #the files inside /etc/cron.d | |
| chown root:root /etc/cron.d/* | |
| chmod go-wx /etc/cron.d/* | |
| chmod -x /etc/cron.d/* | |
| $ cat /etc/cron.allow | |
| barak | |
| $ sudo systemctl restart cron | |
| $ cat /etc/cron.d/barak_job | |
| */1 * * * * barak echo "Nightly Backup Successful: $(date) " > /tmp/test1_job.log | |
| */1 * * * * /usr/bin/free -m | awk '{ if($1 == "Mem:" ) print $3}' | awk '{ if ( $1 > 140 ) print $0; else print "less" }' >> /tmp/memo.log | |
| #troubleshooting cron | |
| $ cat /etc/cron.d/barak_job | |
| */1 * * * * barak echo "Nightly Backup Successful: $(date) " &> /tmp/test1_job.log #redirect stdout and stderr to a file. | |
| */1 * * * * barak echo "Nightly Backup Successful: $(date) " > /tmp/test1_job.log2 2>&1 #redirect stdout and stderr to a file. | |
| #php specific | |
| php /bla/bla/something.php >> /var/logs/somelog-for-stdout.log | |
| #the only difference from the syntax of the user crontabs is that the line specifies the user to run the job as | |
| 00 01 * * * rusty /home/rusty/rusty-list-files.sh #run Rusty's command script as user rusty from his home directory. | |
| /usr/bin/php /home/username/public_html/cron.php #Execute PHP script: | |
| mysqldump -u root -pPASSWORD database > /root/db.sql #MySQL dump: | |
| /usr/bin/wget --spider "http://www.domain.com/cron.php" #Access URL: | |
| $ cat /etc/cron.allow | |
| barak | |
| $ sudo systemctl restart cron/crond | |
| $ cat /etc/cron.d/barak_job | |
| */1 * * * * barak echo "Nightly Backup Successful: $(date)" >> /tmp/mybackup.log | |
| $ crontab -u barak -l | |
| #*/1 * * * * barak echo "Nightly Backup Successful: $(date) runs" >> /tmp/barak_job.log | |
| $ sudo tail -f /var/log/syslog | grep --color=auto CRON | |
| crontab -e | |
| @hourly echo "Nightly Backup Successful: $(date)" >> /tmp/mybackup.log | |
| #"-u borg" is used take the identity of the borg user | |
| # cat /etc/cron.daily/borgbackup_check | |
| #!/bin/bash | |
| sudo -u borg borg check /borgbackup >> /var/log/borgbackup.log | |
| #once every 5 minutes | |
| cat | sudo tee /etc/cron.d/cron-mrtg << EOF | |
| */5 * * * * env LANG=C /usr/bin/mrtg /etc/mrtg.cfg | |
| EOF | |
| #verify | |
| cat /etc/cron.d/cron-mrtg | |
| crontab -l | |
| cat | sudo tee /etc/cron.d/sysinfo << EOF | |
| #once every 5 minutes | |
| */5 * * * * /bin/bash /home/vagrant/sysinfo_func.sh | |
| EOF | |
| #verify | |
| cat /etc/cron.d/cron-mrtg | |
| * * * * * /bin/date >> /tmp/cron_output #This will append the current date to a log file every minute. | |
| * * * * * /usr/bin/php /var/www/domain.com/backup.php > /dev/null 2>&1 #run a script but keep it running in the background | |
| at specific time | |
| 00 15 * * 4 sh /root/test.sh | |
| 35 21 * * 7 /bin/date >> /tmp/cron_output | |
| every 5 minutes | |
| */5 * * * * mycommand | |
| an hourly cron job but run at minute 15 instead (i.e. 00:15, 01:15, 02:15 etc.): | |
| 15 * * * * [command] | |
| once a day, at 2:30am: | |
| 30 2 * * * [command] | |
| once a month, on the second day of the month at midnight (i.e. January 2nd 12:00am, February 2nd 12:00am etc.): | |
| 0 0 2 * * [command] | |
| on Mondays, every hour (i.e. 24 times in one day, but only on Mondays): | |
| 0 * * * 1 [command] | |
| three times every hour, at minutes 0, 10 and 20: | |
| 0,10,20 * * * * [command] | |
| # Stop download Mon-Fri, 6am | |
| 0 6 * * 1,2,3,4,5 root virsh shutdown download | |
| */5 * * * * /path/to/some-script.sh #every 5 minutes | |
| @reboot /scripts/script.sh #tasks to execute on system reboot | |
| @hourly /scripts/script.sh #execute on an hourly. | |
| 0 * * * */scripts/script.sh #execute on an hourly. | |
| @daily /scripts/script.sh # execute on a daily basis. | |
| 0 2 * * * /scripts/script.sh # executes the task in the second minute of every day.# | |
| @weekly /bin/script.sh #execute on a weekly basis | |
| 0 0 4 * sun /bin/script.sh #execute on a weekly basis | |
| @monthly /scripts/script.sh #execute on a monthly basis | |
| 0 0 1 * * /scripts/script.sh #execution of a task in the first minute of the month | |
| @yearly /scripts/script.sh #schedule tasks on a yearly basis. | |
| @yearly /scripts/script.sh #executes the task in the fifth minute of every year. | |
| * * * * * sleep 15; /scripts/script.sh #schedule a cron to execute after every 15 Seconds | |
| 0 4,17 * * mon,tue /scripts/script.sh #execute twice on Monday and Tuesday | |
| 0 17 * * mon,wed /script/script.sh #run each Monday and Wednesday at 5 PM | |
| 0 7,17 * * * /scripts/script.sh #execute at 7 AM and 5 PM daily | |
| 0 5 * * mon /scripts/script.sh #execute the task on every Monday at 5 AM | |
| 0 */6 * * * /scripts/script.sh #run a script for 6 hours interval | |
| 0 8-10 * * * /scripts/script.sh # run every hour between 08-10AM | |
| 0 2 * * sat [ $(date +%d) -le 06 ] && /script/script.sh #execute on first Saturday of every month | |
| 0 12 1-7 * * [ "$(date '+\%a')" = "Mon" ] && echo "It's Monday" #on the first Monday of every month | |
| * * * feb,jun,sep * /script/script.sh #run tasks in Feb, June and September months | |
| -------------------------------------------------------------------------------------------------------------------- | |
| tail -n 1 /usr/share/dict/words #limit the number of lines to show | |
| tail -c 24 /usr/share/dict/words #limit the number of bytes to show | |
| tail /usr/share/dict/words /usr/share/dict/french #show the last ten lines of multiple files | |
| tail -n 5 file_1 file_2 | |
| tail -n +N <filename> #the lines starting from line number N | |
| tailf -F /var/log/syslog #monitoring the log file even at its rotation | |
| tail -q /usr/share/dict/words /usr/share/dict/french #suppress the header line pass the -q option | |
| ls -t /etc | tail -n 5 #show the five files or folders modified the longest time ago | |
| #brctl show -> Bridge connections | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #LVM | |
| pvdisplay | |
| pvck | |
| pvs | |
| lvscan | |
| lvdisplay | |
| lvmdiskscan | |
| vgchange | |
| vgscan -a y | |
| e4defrag -cv /path/to/myfiles (defrag folder ) | |
| $ sudo pvcreate /dev/sdb | |
| $ sudo pvs | |
| PV VG Fmt Attr PSize PFree | |
| /dev/sda2 centos lvm2 a-- <63.00g 4.00m | |
| /dev/sdb vg_iscsi lvm2 a-- <30.00g 0 | |
| $ sudo pvdisplay | |
| --- Physical volume --- | |
| PV Name /dev/sdb | |
| VG Name vg_iscsi | |
| PV Size 30.00 GiB / not usable 4.00 MiB | |
| Allocatable yes (but full) | |
| PE Size 4.00 MiB | |
| Total PE 7679 | |
| Free PE 0 | |
| Allocated PE 7679 | |
| PV UUID hG93NW-gvRB-njUP-pgj8-omRF-YzFe-rTMWOz | |
| --- Physical volume --- | |
| PV Name /dev/sda2 | |
| VG Name centos | |
| PV Size <63.00 GiB / not usable 3.00 MiB | |
| Allocatable yes | |
| PE Size 4.00 MiB | |
| Total PE 16127 | |
| Free PE 1 | |
| Allocated PE 16126 | |
| PV UUID rFHI2D-fvZw-Mf2P-gKTC-ZTwt-vdiY-TEQc14 | |
| $ sudo vgcreate vg_iscsi /dev/sdb | |
| $ sudo vgdisplay | |
| --- Volume group --- | |
| VG Name vg_iscsi | |
| System ID | |
| Format lvm2 | |
| Metadata Areas 1 | |
| Metadata Sequence No 2 | |
| VG Access read/write | |
| VG Status resizable | |
| MAX LV 0 | |
| Cur LV 1 | |
| Open LV 0 | |
| Max PV 0 | |
| Cur PV 1 | |
| Act PV 1 | |
| VG Size <30.00 GiB | |
| PE Size 4.00 MiB | |
| Total PE 7679 | |
| Alloc PE / Size 7679 / <30.00 GiB | |
| Free PE / Size 0 / 0 | |
| VG UUID j63noX-S9I0-5Gp0-3FPg-IZ23-oZNK-6qpb7X | |
| $ sudo lvcreate -l 100%FREE -n lv_iscsi vg_iscsi | |
| [vagrant@vg-suricata-30 ~]$ sudo lvscan | |
| ACTIVE '/dev/vg_iscsi/lv_iscsi' [<30.00 GiB] inherit | |
| ACTIVE '/dev/centos/swap' [2.00 GiB] inherit | |
| ACTIVE '/dev/centos/home' [<20.01 GiB] inherit | |
| ACTIVE '/dev/centos/root' [40.98 GiB] inherit | |
| $ sudo lvdisplay | |
| --- Logical volume --- | |
| LV Path /dev/vg_iscsi/lv_iscsi | |
| LV Name lv_iscsi | |
| VG Name vg_iscsi | |
| LV UUID exEdIG-s2bK-vFEa-fD3X-dplu-q2W3-1rTXsE | |
| LV Write Access read/write | |
| LV Creation host, time vg-suricata-30, 2019-12-18 12:35:56 +0000 | |
| LV Status available | |
| # open 0 | |
| LV Size <30.00 GiB | |
| Current LE 7679 | |
| Segments 1 | |
| Allocation inherit | |
| Read ahead sectors auto | |
| - currently set to 8192 | |
| Block device 253:3 | |
| $ sudo vgremove vg_iscsi | |
| $ sudo pvremove /dev/sdb | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #troubleshooting prometheus | |
| #Shutting down Prometheus | |
| lsof -n -i4TCP:9090 #find a process (Prometheus) listening on port 9090 | |
| pgrep -f prometheus | |
| curl -X POST :9090/-/quit | |
| curl -X POST http://localhost:9090/-/quit # (when the --web.enable-lifecycle flag is enabled) | |
| #Prometheus Reload | |
| curl -i -XPOST localhost:9090/-/reload | |
| killall -HUP prometheus | |
| ./promtool check config prometheus.yml #check if prometheus.yml is valid | |
| journalctl --boot | grep prometheus | |
| #reload Prometheus config file | |
| kill -HUP 9783 | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #list open files | |
| lsof | |
| #list open files owned by user1 | |
| lsof -u user1 | |
| #list open file via tcp | |
| lsof -i TCP:1-1024 | |
| lsof -i TCP:80 | |
| PID 27808 | |
| lsof -Pan -p 27808 -i | |
| lsof -p 2 | |
| # troubleshooting #1 | |
| find all the opened files and processes along with the one who opened them | |
| # lsof –p PID | |
| Count number of files & processes | |
| # lsof -p 4271 | wc -l | |
| Check the currently opened log file | |
| lsof –p | grep log | |
| Find out port number used by daemon | |
| # lsof -i -P |grep 4271 | |
| # find out what running processes are associated with each open port on Linux | |
| netstat -nlp|grep 9000 | |
| sudo ss -lptn 'sport = :80' | |
| sudo netstat -nlp | grep :80 | |
| sudo lsof -n -i :80 | grep LISTEN | |
| fuser 3306/tcp | |
| fuser 80/tcp | |
| ss -tanp | grep 6379 | |
| fuser -v -n tcp 22 | |
| sudo netstat -ltnp | grep -w ':80' | |
| netstat -tulpn | grep :80 | |
| netstat -tulpn | |
| ls -l /proc/1138/exe | |
| sudo ss -tulpn | |
| sudo ss -tulpn | grep :3306 | |
| fuser 7000/tcp | |
| ls -l /proc/3813/exe | |
| man transmission | |
| whatis transmission | |
| # find out current working directory of a process pid 3813 | |
| ls -l /proc/3813/cwd | |
| pwdx 3813 | |
| # Find Out Owner Of a Process on Linux | |
| cat /proc/3813/environ | |
| grep --color -w -a USER /proc/3813/environ | |
| lsof -i :80 | grep LISTEN | |
| # The file /etc/services is used to map port numbers and protocols to service names | |
| grep port /etc/services | |
| grep 443 /etc/services | |
| #Start a Linux Process or Command in Background | |
| $ tar -czf home.tar.gz . | |
| $ tar -tvf home.tar.gz # list the contents of a .tar file | |
| $ bg | |
| $ jobs | |
| OR | |
| $ tar -czf home.tar.gz . & | |
| $ jobs | |
| #Keep Linux Processes Running After Exiting Terminal | |
| $ sudo rsync Templates/* /var/www/html/files/ & | |
| $ jobs | |
| $ disown -h %1 | |
| $ jobs | |
| OR | |
| $ nohup tar -czf iso.tar.gz Templates/* & | |
| $ jobs | |
| #Detach a Linux Processes From Controlling Terminal | |
| firefox </dev/null &>/dev/null & | |
| count & | |
| jobs | |
| fg | |
| bg | |
| fg %# #Replace the # with serial number of the job,bring any job in foreground | |
| jobs -l | |
| count 2> /dev/null & | |
| ----------------------------------------------------------------------------------------------------- | |
| 2 is the file descriptor of stderr | |
| the integer file descriptors associated with the streams stdin, stdout, and stderr are 0, 1, and 2, respectively. | |
| a number 0 = standard out (i.e. STDIN) | |
| a number 1 = standard out (i.e. STDOUT) | |
| a number 2 = standard error (i.e. STDERR) | |
| if a number isn't explicitly given, then number 1 is assumed by the shell (bash) | |
| ">" send to as a whole completed file, overwriting target if exists | |
| "echo test > file.txt" is equivalent to "echo test 1> file.txt" | |
| echo test 2> file.txt #redirect stderr to file.txt | |
| "/dev/null" is the null device it takes any input you want and throws it away. | |
| It can be used to suppress any output | |
| "2>/dev/null" | |
| Redirect STDERR to /dev/null (nothing shows up on console) | |
| The general form of this one is "M>/dev/null", where "M" is a file descriptor number. | |
| This will redirect the file descriptor, "M", to "/dev/null". | |
| ">&" is the syntax to redirect a stream to another file descriptor | |
| "echo test 1>&2" equivalent to "echo test >&2" | |
| "2>&1" | |
| The general form of this one is "M>&N", where "M" & "N" are file descriptor numbers. | |
| It combines the output of file descriptors "M" and "N" into a single stream. | |
| "&" indicates that what follows and precedes is a file descriptor, and not a filename. | |
| "2>&-" | |
| closing a file descriptor used with redirection | |
| The general form of this one is "M>&-", where "M" is a file descriptor number. | |
| This will close output for whichever file descriptor is referenced, i.e. "M" | |
| "|&" | |
| Redirect STDERR and STDOUT to STDIN | |
| This is just an abbreviation for "2>&1 |" | |
| "&>/dev/null" | |
| Redirect both STDERR & STDOUT to /dev/null (nothing shows up on console) | |
| This is just an abbreviation for >/dev/null 2>&1. | |
| It redirects file descriptor 2 (STDERR) and descriptor 1 (STDOUT) to /dev/null | |
| ">/dev/null" | |
| Redirect STDOUT to /dev/null (only STDERR shows on console) | |
| This is just an abbreviation for 1>/dev/null. | |
| It redirects file descriptor 1 (STDOUT) to /dev/null. | |
| "command > /dev/null 2>&1 &" #Run command in the background, discard stdout and stderr | |
| "command >> /path/to/log 2>&1 &" #Run command and append stdout and stderr to a log file | |
| ./command >/dev/null 2>&1 #Hide standard and error outputs | |
| Hide standard output | |
| ./command >/dev/null | |
| sends 2 (stderr) into 1 (stdout), and sends stdout to file.log | |
| command > file.log 2>&1 | |
| Hide standard and error outputs and release terminal (run the command in background) | |
| ./command >/dev/null 2>&1 & | |
| prevent standard output and error output, redirecting them both to /dev/null | |
| script > /dev/null 2>&1 | |
| ----------------------------------------------------------------------------------------------------- | |
| #Identify processes using files, directories, or sockets.Who is Using a File or Directory | |
| $ fuser . | |
| $ fuser -v ./ | |
| Check Processes Using TCP/UDP Sockets | |
| fuser -v -n tcp 5000 | |
| the processes that are using my 'home' directory | |
| $ fuser ~ | |
| $ fuser ~ -v | |
| check for the root directory | |
| $ fuser / | |
| $ fuser / -v | |
| $ fuser -v /home/ismail | |
| $ fuser -v -m /home/ismail/.bashrc | |
| $ fuser -v -n tcp 8080 | |
| $ fuser -v -n udp 53 | |
| kill this TCP listener, you can use option -k | |
| $ fuser -i -k 8080/tcp | |
| shows all processes at the (local) TELNET port | |
| $ fuser telnet/tcp | |
| list signals | |
| $ fuser -l | |
| STOP a process | |
| $ fuser -i -k STOP [FILE/DIRECTORY] | |
| kills all processes accessing the file system /home | |
| $ fuser -km /home | |
| $ who #logged-in users,List Connected Users | |
| #all the currently logged in users, the time of login and their host machine's IP address. | |
| #review the contents of the /var/log/utmp file | |
| $ who -H | |
| $ who -r | |
| run-level 5 2018-07-14 17:16 | |
| $ runlevel ->‘N’ indicates that the runlevel has not been changed since the system was booted. And, "number" is the current runlevel | |
| The last run level, and the current run level. | |
| $ runlevel | |
| md5sum ubuntu-6.10-desktop-i386.iso | |
| sha256sum ubuntu-9.10-dvd-i386.iso | |
| echo "$(cat kubectl.sha256) kubectl" | sha256sum --check # Validate the kubectl binary against the checksum file | |
| sha1sum filename #view the SHA-1 of a file | |
| sha1sum -c DNi70074.bio.sha1 #read SHA1 sums from the FILEs and check | |
| sha1sum --check --ignore-missing DNi70074.bio.sha1 # Do not fail or report status for missing files | |
| $ wget https://github.com/coreruleset/coreruleset/archive/refs/tags/v3.3.2.zip | |
| $ echo -n '88f336ba32a89922cade11a4b8e986f2e46a97cf v3.3.2.zip' | sha1sum -c - | |
| v3.3.2.zip: OK | |
| $ sha1sum v3.3.2.zip | |
| 88f336ba32a89922cade11a4b8e986f2e46a97cf v3.3.2.zip | |
| #watch is used to run any designated command at regular intervals. | |
| watch -n 5 "ls -l | wc l" | |
| -------------------------------------------------------------------------------------------------------------------- | |
| # detect driver hardware problems | |
| dmesg | more | |
| The output of dmesg is maintained in the log file | |
| /var/log/dmesg | |
| cat /var/log/dmesg | less | |
| data from /dev/kmsg | |
| use syslog | |
| # dmesg -S | |
| # limit the output to only error and warnings | |
| dmesg --level=err,warn | |
| # dmesg produce timestamps | |
| dmesg --level=err -T | |
| dmesg -T | grep -i eth0 | |
| dmesg --level=err,warn -T | grep -i eth0 | |
| # limit dmesg's output only to userspace messages | |
| dmesg -u | |
| # timestmaps along with decode facility and levels in dmesg command output | |
| dmesg -Tx | |
| Supported log levels (priorities): | |
| emerg - system is unusable | |
| alert - action must be taken immediately | |
| crit - critical conditions | |
| err - error conditions | |
| warn - warning conditions | |
| notice - normal but significant condition | |
| info - informational | |
| debug - debug-level messages | |
| dmesg -TL -f kern | |
| dmesg -TL -f daemon | |
| Supported log facilities: | |
| kern - kernel messages | |
| user - random user-level messages | |
| mail - mail system | |
| daemon - system daemons | |
| auth - security/authorization messages | |
| syslog - messages generated internally by syslogd | |
| lpr - line printer subsystem | |
| news - network news subsystem | |
| # verify vt-d is ON | |
| "dmesg | grep Virtualization" | |
| # dmesg | grep -i memory | |
| # dmesg | grep -i dma | |
| # dmesg | grep -i usb | |
| # dmesg | grep -E "memory|dma|usb|tty" | |
| # dmesg | grep -E "sda|dma" | |
| Clear dmesg logs | |
| # dmesg -C | |
| # dmesg -c | |
| Display colored messages | |
| # dmesg -L | |
| Monitor real time dmesg logs | |
| # dmesg --follow | |
| # dmesg -Tx --follow | |
| # watch "dmesg | tail 7-20" | |
| Display raw message buffer | |
| # dmesg -r | |
| #virtual machine check | |
| $ dmesg |grep -i hypervisor | |
| -------------------------------------------------------------------------------------------------------------------- | |
| $ dmidecode -s system-manufacturer | |
| -------------------------------------------------------------------------------------------------------------------- | |
| #32x 64x query | |
| uname –m | |
| arch | |
| #linux version | |
| lsb_release -a | |
| cat /etc/issue | |
| cat /etc/os-release | |
| cat /etc/lsb-release | |
| cat /etc/*-release | |
| cat /proc/version | |
| hostnamectl set-hostname server1 | |
| hostnamectl set-hostname --pretty "Web dev test environment" | |
| hostnamectl set-hostname --static webdev-test-env | |
| $ hostname --ip-address | |
| $ hostname --all-ip-addresses | |
| dnsdomainname -f | |
| #create file w multiple lines | |
| echo \ | |
| "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu \ | |
| $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null | |
| sudo ls -hal /tmp/ | sudo tee /tmp/test.out > /dev/null #The redirect to /dev/null is needed to stop tee from outputting to the screen | |
| sudo ls -hal /tmp/ | sudo bash -c "cat >> /tmp/test.out" #To append instead of overwriting the output file METHOD1 | |
| sudo ls -hal /tmp/ | sudo tee /tmp/test.out #To append instead of overwriting the output file METHOD2 | |
| sudo ls -hal /tmp/ | sudo tee --append /tmp/test.out #To append instead of overwriting the output file METHOD2 | |
| # append text with non-root user | |
| echo "deb http://research.cs.wisc.edu/htcondor/ubuntu/8.8/bionic bionic contrib" |sudo tee -a /etc/apt/sources.list | |
| #do not see the contents of the website (may receive an access denied or ‘bad bot’ message) | |
| curl -A 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.140 Safari/537.36' URL | |
| curl --compressed URL | |
| curl URL | iconv -f windows-1251 -t UTF-8 #convert from the windows-1251 encoding to the UTF-8 encoding | |
| curl -u username:password URL #websites require a username and password to view their content,specify other authentication methods using --ntlm | --digest | |
| #showing only headers, HTML code not displayed | |
| curl -s -I -A 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.140 Safari/537.36' https://www.acrylicwifi.com/AcrylicWifi/UpdateCheckerFree.php?download | grep -i '^location' | |
| curl -s -v http://www.paterva.com/web7/downloadPaths41.php -d 'fileType=exe&os=Windows' 2>&1 | grep -i 'Location:' | |
| #save cookies,data transfer using the POST method, the --data option is used | |
| curl --cookie-jar cookies.txt http://forum.ru-board.com/misc.cgi --data 'action=dologin&inmembername=f123gh4t6&inpassword=111222333&ref=http%3A%2F%2Fforum.ru-board.com%2Fmisc.cgi%3Faction%3Dlogout' | |
| #get information from a page that only registered users have access to, specify the path to the file with previously saved cookies | |
| curl -b cookies.txt 'http://forum.ru-board.com/topic.cgi?forum=35&topic=80699&start=3040' | iconv -f windows-1251 -t UTF-8 | |
| #extracting entire archive | |
| curl -L -o ds.tar.gz https://downloads.dockerslim.com/releases/1.37.3/dist_linux.tar.gz | |
| tar -xvf ds.tar.gz -C /usr/local/bin | |
| tar xvzf tkn_0.10.0_Darwin_x86_64.tar.gz -C /usr/local/bin tkn | |
| tar xjvf backup.tbz | |
| tar -zxvf backup.tar.gz | |
| tar -xf file_name.tar.gz --directory /target/directory | |
| wget --no-check-certificate https://www.cacti.net/downloads/cacti-latest.tar.gz | |
| tar -zxvf cacti-latest.tar.gz | |
| mv cacti-1* /opt/cacti | |
| (OR tar -xf cacti-latest.tar.gz --directory /opt/cacti) | |
| tar -zxvf /tmp/onos-1.12.0.tar.gz --strip-components 1 --directory /opt --one-top-level=onos | |
| tar xvf mysql-5.7.23-linux-glibc2.12-x86_64.tar.gz --one-top-level=mysql57 --strip-components 1 | |
| tar zxvf ugly_name.tgz --one-top-level=pretty_name | |
| #extract .xz file | |
| unxz tor-browser-linux32-5.5.4_en-US.tar.xz | |
| tar xvf tor-browser-linux32-5.5.4_en-US.tar | |
| #extract .bz2 file | |
| bzip2 -dk FileZilla_3.29.0_x86_64-linux-gnu.tar.bz2 | |
| tar xvf FileZilla_3.29.0_x86_64-linux-gnu.tar | |
| #extract .zip file | |
| unzip terraform_0.11.7_linux_amd64.zip -d terraform | |
| #extract .rar file | |
| unrar e extract.rar r | |
| # create user home directory backup | |
| tar cvf filename.tar /home/vagrant/ | |
| # show which files were changed | |
| tar dvf filename.tar | |
| # update the changed files | |
| tar uvf filename.tar | |
| # make smaller backup | |
| gzip filename.tar | |
| #format a USB storage device with FAT32 file system | |
| mkfs –t vfat <USB-device-mount-point> | |
| # mount -o loop,offset=$((10860003 * 512)) disk.img /mnt | |
| #find out the USB device mount point | |
| fdisk -l | |
| #unmount the drive,you can’t format a mounted drive. | |
| sudo umount /dev/sdb1 | |
| sudo mkfs.vfat /dev/sdb1 | |
| sudo mkfs.ntfs /dev/sdb1 | |
| mkfs.ext4 <USB-device-mount-point> | |
| mkfs.ntfs <USB-device-mount-point> | |
| #Set label name to USB drives | |
| sudo mkfs.vfat /dev/sdb1 -n sk | |
| ========================================================================================================== | |
| #Create a New Sudo User(CentOS) | |
| adduser username | |
| passwd username | |
| usermod -aG wheel username #add user to the wheel group.By default, on CentOS, members of the wheel group have sudo privileges | |
| su - username # switch to the new user account | |
| #verify if user is sudoer | |
| sudo -l -U userjohndoe #list user's privileges or check a specific command | |
| sudo --validate / sudo -v #update the user's cached credentials, authenticating the user if necessary | |
| sudo --list #print the list of allowed and forbidden commands for the user who is executing the sudo command | |
| groups #verify if user is sudoer, member of wheel group | |
| sudo whoami # returns root | |
| ---------------------------------------------------------------------------------------------------- | |
| #Create a New Sudo User (ubuntu) | |
| sudo adduser barak #create new user | |
| sudo adduser barak sudo #Add the user to sudo group | |
| usermod -aG sudo barak #Add the user to sudo group | |
| id barak #verify sudo group | |
| groups newuser #verify sudo group | |
| su - barak #Verify Sudo Access | |
| $ ls /root | |
| ls: cannot open directory '/root': Permission denied | |
| sudo ls /root | |
| ---------------------------------------------------------------------------------------------------- | |
| echo $HOME $USER | |
| sudo bash -c 'echo $HOME $USER' | |
| sudo -H bash -c 'echo $HOME $USER' | |
| #-H flag makes sudo assume root's home directory as HOME instead of the current user's home directory | |
| sudo -H | |
| #sudo user | |
| echo "stack ALL=(ALL) NOPASSWD: ALL" |sudo tee -a /etc/sudoers | |
| #allow a user aaron to run all commands using sudo without a password, open the sudoers file | |
| $ sudo visudo | |
| aaron ALL=(ALL) NOPASSWD: ALL | |
| %sys ALL=(ALL) NOPASSWD: ALL #all member of the sys group will run all commands using sudo without a password | |
| alf ALL=(ALL) NOPASSWD: ALL #permit a user to run a given command (/bin/kill) using sudo without a password | |
| %sys ALL=(ALL) NOPASSWD: /bin/kill, /bin/rm #the sys group to run the commands: /bin/kill, /bin/rm using sudo without a password | |
| #su vs sudo | |
| #"sudo" asks for your password,"su" asks for the password for the user whom you are switching to | |
| #sudo lets you issue commands as another user without changing your identity,entry in /etc/sudoers to execute these restricted permissions | |
| #without entering the root password | |
| #su keeps the environment of the old/original user even after the switch to root | |
| #creates a new environment (as dictated by the ~/.bashrc of the root user), | |
| #similar to the case when you explicitly log in as root user from the log-in screen. | |
| "su -" | |
| "su -l" #pass more arguments | |
| "su -c" #su [target-user] -c [command-to-run] a command that you want to run after switching to the target user. | |
| su -c '/home/annie/annie-script.sh' annie #While logged in as user dave, run the annie-script.sh as user annie | |
| su -c 'echo I am $(whoami)' #Without specifying a target user,switch into root | |
| #The password prompt is not preferable, during scripting | |
| #disable the password prompt when user dave is executing scripts as user annie.dave uses su without having to input annie‘s password. | |
| #/etc/pam.d/su,add the following lines right after the line "auth sufficient pam_rootok.so" | |
| auth [success=ignore default=1] pam_succeed_if.so user = annie #rule checks if the target user is annie | |
| auth sufficient pam_succeed_if.so use_uid user = dave #rule to check if the current user is dave | |
| su -c /home/annie/annie-script.sh annie #run by dave | |
| auth sufficient pam_rootok.so | |
| auth [success=ignore default=1] pam_succeed_if.so user = otheruser | |
| auth sufficient pam_succeed_if.so use_uid user ingroup somegroup | |
| #/etc/sudoers | |
| echo 'dave ALL=(annie) /home/annie/annie-script.sh' | EDITOR='tee -a' visudo #The rule grants dave the permission to execute the script annie-script.sh as user annie on any hosts | |
| sudo -u annie /home/annie/annie-script.sh #while logged in as dave | |
| sudo -u root /home/annie/annie-script.sh #Sorry, user dave is not allowed to execute '/home/annie/annie-script.sh' as root | |
| "sudo -s" or "sudo -i" #mimic "su" or "su -l" | |
| "sudo -s or sudo -i" #temporarily become a user with root privileges | |
| #/etc/sudoers | |
| echo 'dave ALL=(ALL) /home/annie/annie-script.sh' | EDITOR='tee -a' #The rule grants dave to execute the script annie-script.sh as any users | |
| sudo -u root /home/annie/annie-script.sh #while logged in as dave | |
| #The password prompt is not preferable, during scripting | |
| #/etc/sudoers | |
| dave ALL=(ALL) NOPASSWD: /home/annie/annie-script.sh' | EDITOR='tee -a' | |
| # switching to root using sudo -i (or sudo su) cancels auditing/logging | |
| # when a sudo command is executed, the original username and the command are logged | |
| "sudo su" | |
| "sudo -i" | |
| su is equivalent to sudo -i | |
| gives you the root environment, i.e. your ~/.bashrc is ignored. | |
| simulates a login into the root account | |
| Your working directory will be /root | |
| will read root's .profile | |
| "sudo -s" | |
| gives you the user's environment, so your ~/.bashrc is respected. | |
| launches a shell as root | |
| doesn't change your working directory | |
| "sudo bash" #runs bash as a super user | |
| sudo -E #The -E (preserve environment) option indicates to the security policy that the user wishes to preserve their existing environment variables. | |
| ========================================================================================================== | |
| mount -l | |
| lshw -short | |
| sudo lshw -class disk | |
| sudo lshw -short -class disk | |
| lshw -class processor | |
| file -Ls | |
| dmesg | |
| denyhosts | |
| vmstat | |
| w | |
| uptime | |
| ps | |
| free | |
| iostat | |
| pmap | |
| paste | |
| uname | |
| sudo | |
| mkdir | |
| chown | |
| ptree | |
| pkill | |
| killall | |
| kill -KILL PID | |
| kill –TERM [PID] #means terminate.the default signal sent by kill,equivalent to kill <PID> | |
| kill –HUP [PID] #reset or restart the process | |
| all signals | |
| $ kill -l | |
| stop and restart process | |
| $ kill -1 13980 | |
| 1 SIGHUP | |
| 9 SIGKILL stop process without letting gracefully | |
| 15 SIGTERM stop process | |
| ------------------------------------------------------------------------------------------------------------------ | |
| $ touch mylog | |
| $ ls -lai mylog | |
| 3145761 -rw-rw-r-- 1 vagrant vagrant 0 Mar 27 21:01 mylog | |
| update the access time of existing file | |
| $ touch -c mylog | |
| Change file access time - 'a' of existing file | |
| $ touch -a mylog | |
| Change the modified time '-m' of existing file | |
| $ touch -m mylog | |
| $ touch -am mylog | |
| Set a specific access/modify time instead of current time, specify the datetime in format [[CC]YY]MMDDhhmm[.ss] | |
| $ touch -c -t 201603051015 mylog | |
| $ touch -c -d '5 Jan 2009' mylog | |
| $ touch -c -d '20:30' myfile | |
| Use the timestamp of another file as reference | |
| $ touch myfile -r mylog | |
| use the timestamps of 'apl' for 'apl.c' | |
| $ touch apl.c -r apl | |
| $ ls -lai mylog | |
| 3145761 -rw-rw-r-- 1 vagrant vagrant 0 Mar 27 21:06 mylog | |
| $ stat mylog | |
| File: 'mylog' | |
| Size: 0 Blocks: 0 IO Block: 4096 regular empty file | |
| Device: fc00h/64512d Inode: 3145761 Links: 1 | |
| Access: (0664/-rw-rw-r--) Uid: ( 1000/ vagrant) Gid: ( 1000/ vagrant) | |
| Access: 2019-03-27 21:07:54.953000000 +0000 | |
| Modify: 2019-03-27 21:07:54.953000000 +0000 | |
| Change: 2019-03-27 21:07:54.953000000 +0000 | |
| Birth: - | |
| force touch to not create any new file | |
| $ touch -c newfile | |
| $ ls -l newfile | |
| ls: cannot access 'newfile': No such file or directory | |
| $ stat newfile | |
| stat: cannot stat 'newfile': No such file or directory | |
| ------------------------------------------------------------------------------------------------------------------ | |
| # create symbolic link | |
| ln -s test1.txt symbolic_test1.txt | |
| stat symbolic_test1.txt | |
| touch -c -d '5 Jun 2001' -h symbolic_test1.txt | |
| stat symbolic_test1.txt | |
| # detect symbolic link | |
| touch a.xt | |
| ln -s a.txt b.txt | |
| stat b.txt | |
| file b.txt | |
| ln -s source.file softlink.file | |
| ls -lia #does not share the same inode number and permissions of original file | |
| rm source.file | |
| stat softlink.file #No such file or directory | |
| # create hard link | |
| ln source.file hardlink.file | |
| ls -lia #shares the same inodes number and permissions of original file | |
| rm source.file | |
| stat hardlink.file | |
| echo "hola el mundo" >>source.file #change the content of either of the files, the change will be reflected | |
| cat hardlink.file | |
| cat source.file | |
| lscpiu | |
| stat file.txt | |
| #standard output activities for each available processor | |
| mpstat | |
| mpstat -P ALL 2 2 | |
| ---------------------------------------------------------------------------------------------------- | |
| df –h # view the amount of free disk space | |
| df -HT #Display File System Type | |
| df -hT /home | |
| df -t ext3 #display a certain file system type use the ‘-t‘ option | |
| df -x ext3 #Exclude Certain File System Type | |
| df -k #usage in 1024-byte blocks, use the option ‘-k‘ | |
| df -m # MB (MegaByte) | |
| df -i # view number of inodes in the system | |
| df -kl # get a detail description on disk space usage | |
| --------------------------------------------------------------------------------------------------- | |
| du -sh /* # list directory sizes under root / disk | |
| du -sh /* | sort -h | |
| du -m /some/path | sort -nr | head -n 20 #sorted list containing the 20 biggest dirs | |
| for each in $(ls) ; do du -hs "$each" ; done | |
| du --threshold=1M -h | sort -h #includes hidden dot folders (folders which start with .). | |
| du -h | sort -h 3 | |
| du -bch #-b gives you the file size instead of disk usage, and -c gives a total at the end | |
| du -ch | tail -1 | |
| du -sh /some/dir #the summary of a grand total disk usage size of an directory use the option “-s” | |
| du -sh /var/* |grep G | |
| du -ah /home/tecmint # displays the disk usage of all the files and directories | |
| du -kh /home/tecmint #the disk usage of a directory tree with its subtress in Kilobyte blocks. Use the “-k” (displays size in 1024 bytes units). | |
| du -kh /home/tecmint #Megabytes (MB) | |
| du -ch /home/tecmint #The “-c” flag provides a grand total usage disk space at the last line | |
| du -ah --exclude="*.txt" /home/tecmint | |
| du -ha --time /home/tecmint #the disk usage based on modification of time, use the flag “–time” | |
| #The problem with du is that it adds up the size of the directory nodes as well,not to sum up only the file sizes. | |
| # total size of files in a directory | |
| du -h -c directory #listing path | |
| du -h -c directory|tail -1 #only total size | |
| $ du -sh /var/log/apt #only total size and listing | |
| #du prints actual disk usage rounded up to a multiple of (usually) 4 KB instead of logical file size | |
| $ for i in {0..9}; do echo -n $i > $i.txt; done #create files | |
| $ ls *.txt | |
| 0.txt 1.txt 2.txt 3.txt 4.txt 5.txt 6.txt 7.txt 8.txt 9.txt | |
| $ du -ch *.txt | tail -1 | |
| 40K total | |
| $ ls -FaGl *.txt | printf "%'d\n" $(awk '{SUM+=$4}END{print SUM}') | |
| 10 | |
| du /var/* -shc --exclude=lib #--exclude to exclude any directory | |
| du /var/ -h --exclude=lib --max-depth=1 #first-level sub-directories in the /var/ directory. | |
| $ du -ch /var/log/apt | tail -1 | cut -f 1 | |
| $ du -ac --bytes /var/log/apt | |
| $ du -ac --bytes /var/log/apt | grep "log$" | awk '{ print; total += $1 }; END { print "total lobsters: ", total, " Bytes" }' | |
| $ du -ac --bytes /var/log/apt | grep "log$" | awk '{ print; total += $1 }; END { print "total lobsters: ", total/1024, " KB" }' | |
| $ du -ac --bytes /var/log/apt | grep "log$" | awk '{ print; total += $1 }; END { print "total lobsters: " total/1024/1024 " MB" }' | |
| $ du /var/log/apt/*.log | awk '{ print; total += $1 }; END { print "total size: ",total }' | |
| ---------------------------------------------------------------------------------------------------- | |
| $ dir /var/log/apt #list directory contents | |
| $ dir /var/log/apt | tee >( awk '{ total += $4 }; END { print total }' ) #list directory contents and total size | |
| $ dir /var/log/apt | awk '{ print; total += $4 }; END { print "total size: ",total }' #total size | |
| ---------------------------------------------------------------------------------------------------- | |
| #List all running processes containing the string stuff | |
| cat /proc/cpuinfo | |
| grep "physical id" /proc/cpuinfo | wc -l | |
| cat /proc/meminfo | |
| grep MemTotal /proc/meminfo | awk '{FS=":"}{print $2 }' | awk '{print $1/1024/1024}' | |
| cat /proc/zoneinfo | |
| cat /proc/mounts | |
| cat /etc/issue | |
| # missing files | |
| $ sudo ls -lai /lost+found/ | |
| # errors about a corrupt superblock on the drive | |
| $ e2fsck -b 8193 | |
| $list files sorted by size | |
| ls –lSr | |
| ls -il | |
| #get pid of my_app | |
| my_app & $! | |
| pidof lighttpd -> Find PID of A Program/Command | |
| pidof -s php5-cgi | |
| pidof -x fetch-data -> Get pids of scripts | |
| pidof -o 4242 lighttpd -> ignore or omit processes,useful to ignore calling shell or shell script or specific pid. | |
| ------------------------------------------------------------------------------------------ | |
| # history,The ! prefix is used to access previous commands. | |
| !$ - last argument from previous command(last command) | |
| !:1 # last command's 1st argument | |
| !:2 # last command's 2nd argument | |
| !:1-2 # last command's 1st and 2nd argument | |
| !^ - first argument (after the program/built-in/script) from previous command | |
| !* - all arguments from previous command | |
| !! - previous command (often pronounced "bang bang") | |
| !n - command number n from history | |
| !pattern - most recent command matching pattern | |
| !!:s/find/replace - last command, substitute find with replace | |
| !3:2 #take the second argument from the third command in the history | |
| !-5:3 #take the third argument from the fifth last command in the history,Using a minus sign to traverse from the last command of the history | |
| $ echo 'one' 'two' | |
| one two | |
| $ !$ | |
| 'two' | |
| $ !^ | |
| 'one' | |
| $ !* | |
| 'one' 'two' | |
| $ !! | |
| echo 'one' 'two' | |
| one two | |
| $ ls /tmp && cd !* | |
| ------------------------------------------------------------------------------------------ | |
| $ curl -kL http://localhost/banana | |
| #curl -IL http://localhost | |
| HTTP/1.1 200 OK | |
| Server: nginx/1.10.2 | |
| curl -Is http://www.google.com | head -n 1 #check whether a web site is up, and what status message the web server is showing | |
| curl -sSf http://example.org > /dev/null | |
| curl -XGET 'localhost:9200/?pretty' | |
| curl -X PUT "http://127.0.0.1:9200/mytest_index" #sending data with POST and PUT requests | |
| curl -d "param1=value1¶m2=value2" -X POST http://localhost:3000/data | |
| curl -d "param1=value1¶m2=value2" -H "Content-Type: application/x-www-form-urlencoded" -X POST http://localhost:3000/data | |
| curl -d "@data.txt" -X POST http://localhost:3000/data | |
| curl -d '{"key1":"value1", "key2":"value2"}' -H "Content-Type: application/json" -X POST http://localhost:3000/data | |
| curl -d "@data.json" -X POST http://localhost:3000/data | |
| # check if apache is running | |
| curl -sf http://webserver/check_url | |
| # process was holding a particular port open | |
| ss -tp state listening sport = :80 | grep httpd | |
| # check a particular process id | |
| lsof -p 1036 -P | grep 'TCP \*:80' | |
| $ echo "The process id is" $$ | |
| $ echo "The process id is" $$$$ | |
| # check what process is listening | |
| $ sudo fuser -n tcp 22 | |
| 22/tcp: 1088 14324 14354 | |
| echo $SHELL -> determine current shell type | |
| cat /proc/cpuinfo | grep 'vmx\|svm' -> VT-x/AMD-v virtualization is enabled in BIOS | |
| # testing nginx | |
| journalctl -u nginx.service | |
| nginx -t | |
| sudo ss -tulpn # Verify that port 80 or 443 | |
| curl -I http://10.21.136.13 | |
| curl http://10.21.136.13 | |
| dig +short localhost @8.8.8.8 | |
| ------------------------------------------------------------------------------------------------ | |
| #/etc/systemd/journald.conf | |
| #SystemMaxUse=100M | |
| cat /etc/systemd/journald.conf | grep SystemMaxUse | |
| journalctl --vacuum-size=100M | |
| sudo usermod -a -G systemd-journal $USER # add the current user to the systemd-journal group | |
| # process the data further with text processing tools like grep, awk, or sed, or redirect the output to a file | |
| journalctl --no-pager #print its output directly to the standard output instead of using a pager by including the --no-pager flag | |
| journalctl -o json -n 10 --no-pager #change the format to format like JSON | |
| journalctl -o json-pretty -n 10 --no-pager | |
| sudo mkdir -p /var/log/journal | |
| ls -l /var/log/journal/3a0d751560f045428773cbf4c1769a5c/ | |
| sudo cp /etc/systemd/journald.conf{,.orig} | |
| sed -i 's/#Storage.*/Storage=persistent/' /etc/systemd/journald.conf # set "Storage" type to "persistent | |
| sudo vi /etc/systemd/journald.conf | |
| Storage=persistent | |
| systemctl restart systemd-journald.service | |
| journalctl --flush # move the journal log files from /run/log/journal to /var/log/journal | |
| #The options prefixed with "Runtime" apply to the journal files when stored on a volatile in-memory file system, | |
| #more specifically /run/log/journal | |
| journalctl --vacuum-files=2 # have 10 archived journal files and want to reduce these down to 2 | |
| journalctl --verify | |
| journalctl | head -1 #What time range do I have logs for? | |
| journalctl -F _SYSTEMD_UNIT #What systemd services do I have logs for? | |
| journalctl -F _COMM | |
| journalctl -F _EXE | |
| journalctl -F _CMDLINE | |
| #What users do the services that logged something run as (swap _UID/-u with _GID/-g for groups)? | |
| journalctl -F _UID | xargs -n1 id -nu | |
| journalctl -F _UID | xargs -n1 id -ng | |
| #provide test input for journalctl | |
| logger -p err 'something erronous happened' | |
| systemd-cat -p info echo 'something informational happened' | |
| #What selector fields are there? Show up to 8 values each | |
| for f in $(sudo journalctl --fields); do | |
| echo ===========$f; | |
| sudo journalctl -F $f; | |
| done | grep -A8 ======== | |
| #remove all entries | |
| journalctl --rotate | |
| journalctl --vacuum-time=1s | |
| journalctl -m --vacuum-time=1s #-m flag, it merges all journals and then clean them up | |
| #remove all entries | |
| find /var/log/journal -name "*.journal" | xargs sudo rm | |
| systemctl restart systemd-journald | |
| #remove all entries | |
| rm -rf /run/log/journal/* | |
| journalctl --rotate --vacuum-size=500M #rotate journal files and remove archived journal files until the disk space they use is under 500M | |
| #Rotating is a way of marking the current active log files as an archive and create a fresh logfile from this moment | |
| # The flush switch asks the journal daemon to flush any log data stored | |
| #in /run/log/journal/ into /var/log/journal/, if persistent storage is enabled. | |
| #Manual delete,removes all archived journal log files until the last second,clears everything | |
| journalctl --flush --rotate #applies to only archived log files only, not on active journal files | |
| journalctl --vacuum-time=1s | |
| #Manual delete,clears all archived journal log files and retains the last 400MB files | |
| journalctl --flush --rotate | |
| journalctl --vacuum-size=400M | |
| #Manual delete,only the last 2 journal files are kept and everything else is removed | |
| journalctl --flush --rotate | |
| journalctl --vacuum-files=2 | |
| journalctl -b ->all of the journal entries that have been collected since the most recent reboot | |
| journalctl --list-boots #list of boot numbers, their IDs, and the timestamps of the first and last message pertaining to the boot | |
| journalctl --boot=ID _SYSTEMD_UNIT=foo | |
| journalctl -b -1 -> see the journal from the previous boot,use boot number to pick specific boot | |
| journalctl -k -b -1 -> Shows kernel logs for the current boot. | |
| $ journalctl --list-boots #list boot id | |
| -1 340f8a96d40749f8b2530cc76810d62d Tue 2022-01-18 14:33:46 +03—Tue 2022-01-18 15:14:42 +03 | |
| 0 75c35ddeb4274787ad78d1092bf9743a Tue 2022-01-18 23:08:10 +03—Wed 2022-01-19 09:25:35 +03 | |
| $ journalctl -b 75c35ddeb4274787ad78d1092bf9743a #use boot id | |
| journalctl --since "2015-01-10 17:15:00" | |
| journalctl -S "2020-91-12 07:00:00" | |
| journalctl -S -1d #The “d” stands for “day”, and the “-1” means one day in the past | |
| journalctl -S -1h | |
| journalctl --since "2015-06-26 23:15:00" --until "2015-06-26 23:20:00" | |
| journalctl -S "2020-91-12 07:00:00" -U "2020-91-12 07:15:00" | |
| journalctl --since yesterday | |
| journalctl -S yesterday | |
| journalctl --since yesterday --until now | |
| journalctl --since today | |
| journalctl -S -2d -U today #everything from two days ago up until the start of today | |
| journalctl --since 09:00 --until "1 hour ago" | |
| journalctl --since '1h ago' --until '10 min ago' | |
| #syslog log levels i.e. "emerg" (0), "alert" (1), "crit" (2), "err" (3), "warning" (4), "notice" (5), "info" (6), "debug" (7) | |
| journalctl -p 0 | |
| journalctl -p 0..2 # logs for a range between emerg(0) and critical(2) | |
| journalctl -f -p warning # show me warnings | |
| journalctl -p err # show all errors | |
| journalctl -xp info | |
| journalctl -xu sshd | |
| journalctl -fxu httpd.service | |
| journalctl -fxu sshd.service -p debug | |
| journalctl -fx | |
| journalctl -xn | |
| journalctl /dev/sda -> displays logs related to the /dev/sda file system. | |
| journalctl /sbin/sshd #logs from the sshd binary | |
| journalctl -n20 _EXE=/usr/sbin/sshd | |
| journalctl /usr/bin/bash | |
| journalctl -u nginx.service -> see all of the logs from an Nginx unit on our system | |
| journalctl -u nginx.service --since today | |
| journalctl -b -u docker -o json | |
| journalctl -u docker.service --since "2016-10-13 22:00" | |
| journalctl _SYSTEMD_UNIT=sshd.service | |
| journalctl -u sshd.service | |
| journalctl -u sshd.service -x #logs with more details | |
| journalctl _PID=8088 | |
| journalctl -b _SYSTEMD_UNIT=foo _PID=number #logs for systemd-units that match foo and the PID number | |
| #all messages from the foo service process with the PID plus all messages from the foo1 service | |
| journalctl -b _SYSTEMD_UNIT=foo _PID=number + _SYSTEMD_UNIT=foo1 | |
| journalctl -b _SYSTEMD_UNIT=foo _SYSTEMD_UNIT=foo1 #shows logs matching a systemd-unit foo or a systemd-unit foo1 | |
| #Filter logs based on user | |
| id -u www-data | |
| 33 | |
| journalctl _UID=33 --since today | |
| journalctl -k ->Kernel messages, those usually found in dmesg output | |
| journalctl _TRANSPORT=kernel | |
| journalctl -n 20 ->see with a number after the -n | |
| journalctl -n 10 -o short-full #Changing the Display Format | |
| journalctl -n 10 -o verbose | |
| journalctl -n 10 -o json | |
| journalctl -n 10 -o json-pretty | |
| journalctl -n 10 -o cat #see the log entry messages, without time stamps or other metadata | |
| journalctl --disk-usage #using persistent storage then the below output shows the amount of disk used | |
| #removes archived journal files until the disk space they use falls below the specified size | |
| #(specified with the usual "K", "M", "G", "T" suffixes), | |
| journalctl --vacuum-size=1G | |
| journalctl --vacuum-time=1weeks #clear all messages older than one week | |
| journalctl --vacuum-time=2d #Retain only the past two days | |
| journalctl -f -> continuously prints log messages, similar to tail -f | |
| journalctl -u mysql.service -f | |
| journalctl -f -e -p err docker --since today # -e implies -n1000 | |
| #who ran sudo in the past week, what commandline, what PWD and user? | |
| journalctl --since '1 week ago' _COMM=sudo -o json \ | |
| | jq -r '(.__REALTIME_TIMESTAMP|tonumber|(./1e6)|todate) + "\t" + ._CMDLINE + "\t" + .MESSAGE' \ | |
| | column -ts $'\t' | |
| #How many ssh auth errors today? | |
| journalctl -o cat -p err -u ssh --since today | wc -l | |
| #filter specific error | |
| journalctl -o cat -p err | grep "tx hang" | |
| #executables have been logging errors at a loglevel lower than error in the past month? | |
| journalctl --since -1month -p 7..4 -o json | jq -r 'select (.MESSAGE | contains("error")) | ._EXE' | sort -u | |
| #show error logs for a particular version of a service | |
| journactl -p err /opt/fooservice/9e76/bin/fooservice | |
| #Filter by start and end dates and particular PIDs | |
| journalctl _SYSTEMD_UNIT=docker --since '2018–11–01 14:00' --until '2018–11–13 14:00' _PID=123 _PID=456 | |
| ------------------------------------------------------------------------------------------------ | |
| Job for autofs.service failed because a configured resource limit was exceeded. See "systemctl status autofs.service" and "journalctl -xe" for details. | |
| systemctl start autofs | |
| systemctl is-active autofs | |
| systemctl is-active autofs >/dev/null 2>&1 && echo YES || echo NO | |
| ps -aux | grep -i autofs | grep -v grep #grep command was shown in the output, remove this distraction is to add another pipe to grep -v grep | |
| kill -9 `ps -ef | grep '[k]eyword' | awk '{print $2}'` # get the pid from ps command | |
| ps -aux | grep dockerd | grep -v grep | awk '{print $2}' # get the pid from ps command | |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | |
| $ ps aux | grep root #list services running as root | |
| ps aux | grep 3813 | |
| ps -eo pid,user,group,args,etime,lstart | grep '[3]813' | |
| ps aux | grep '[1]616' | |
| ps -eo pid,user,group,args,etime,lstart | grep '[1]616' | |
| ps aux | grep stuff | |
| The init process, with process ID 1, which does nothing but wait around for its child processes to die. | |
| Usually started for /etc/inittab | |
| $ ps -ef| grep init | |
| # see the name of the process | |
| $ sudo ps 1088 14324 14354 | |
| # CPU time, page faults of child processes | |
| ps -Sla | |
| $ ps -lu vagrant | |
| memory information long format | |
| $ ps -lma | |
| signal format | |
| $ ps -sx | |
| controlling terminal | |
| $ ps --tty 1 -s | |
| list of command line arguments | |
| pstree -a | |
| show PIDS for each process name | |
| pstree -p | |
| sort processes with the same ancestor by PID instead of by name,numeric sort | |
| pstree -n | |
| pstree -np | |
| find out the owner of a process in parenthesis | |
| pstree -u | |
| pstree -u vagrant | |
| pstree -unp vagrant | |
| highlight the current process and its ancestors | |
| pstree -h | |
| highlight the specified process | |
| pstree -H 60093 | |
| find ID of a process owned by a specific user | |
| $ pgrep -u vagrant sshd | |
| $ pgrep -u vagrant -d: | |
| list process names | |
| $ pgrep -u vagrant -l | |
| $ pgrep -u vagrant -a | |
| count of matching processes | |
| $ pgrep -c -u vagrant | |
| top -> Checking the Priority of Running Processes | |
| ps -o pid,comm,nice -p 594 -> Checking the Priority of Running Processes | |
| ps -o pid,comm,nice,pri -p $(pidof snmpd) | |
| ps -fl -C "perl test.pl" -> The “NI” column in the ps command output indicates the current nice value (i.e priority) of a process. | |
| ps -p 2053 -o comm= | |
| #NI – is the nice value, which is a user-space concept | |
| #PRI – is the process’s actual priority, as seen by the Linux kernel | |
| ps -o ni $(pidof snmpd) | |
| #Total number of priorities = 140 | |
| #Real time priority range(PR or PRI): 0 to 99 | |
| #User space priority range: 100 to 139 | |
| ps -o ni,pri $(pidof snmpd) | |
| #PR = 20 + NI | |
| #PR = 20 + (-20 to + 19) | |
| #PR = (20 + -20) to (20 + 19) | |
| #PR = 0 to 39 (100 to 139 user space priority range) | |
| ps -o pid,comm,nice,pri -p $(pidof snmpd) | |
| cat /proc/$(pidof snmpd)/stat | awk '{print "priority " $18 " nice " $19}' | |
| ps u $(pgrep snmpd) #ps with headers | |
| #The NI column shows the scheduling priority or niceness of each process | |
| #ranges from -20 to 19, with -20 being the most favorable or highest priority for scheduling | |
| #19 being the least favorable or lowest priority | |
| ps -e -o uid,pid,ppid,pri,ni,cmd | { head -5 ; grep snmpd; } #ps with headers | |
| # priority levels between -20 and 19 | |
| nice -10 perl test.pl -> test.pl is launched with a nice value of 10 when the process is started | |
| nice --10 perl test.pl -> Launch a Program with High Priority | |
| nice #Checking default niceness,the default is 0 | |
| # 0 for none, 1 for real-time, 2 for best-exertion, 3 for inactive | |
| ionice -c 3 -p 1 #PID as 1 to be an idle I/O process | |
| ionice -c 2 bash #run ‘bash’ as a best-effort program | |
| ionice -p 3467 #examine the class and priority used by PID 3467 | |
| ionice -c 1 -n 3 -p 3467 | |
| #set the I/O scheduling class to Idle,takes longer,no longer performance degradation | |
| # for pid in $(pidof rsync); do ionice -c 3 -p $pid; done | |
| renice -n -19 -p 3534 -> Change the Priority of a Running Process | |
| /etc/security/limits.conf -> set the default nice value of a particular user or group | |
| gpg --verify gnupg-2.2.3.tar.bz2.sig gnupg-2.2.3.tar.bz2 -> check the signature of the file gnupg-2.2.3.tar.bz2 | |
| systemd-analyze #the actual boot time of the machine | |
| systemd-analyze blame #see how long every program and service takes to start up | |
| systemd-analyze critical-chain # print out the results in a chain of events style | |
| systemd-analyze critical-chain ntp.service networking.service | |
| systemd-analyze plot > boot_analysis.svg | |
| xviewer boot_analysis.svg | |
| systemd-analyze time -H [email protected] #view information from a remote host over ssh | |
| systemd-analyze blame -H [email protected] | |
| systemd-cgtop #top control groups by their resource usage such as tasks, CPU, Memory, Input, and Output | |
| ----------------------------------------------------------------------------------------------------- | |
| PARSING JSON FILE | |
| sudo apt-get install -y jq | |
| curl -s 'https://api.github.com/users/lambda' | jq -r '.name' | |
| grep -w \"key_name\" /vagrant/test.json |tail -1 | cut -d\" -f4 | |
| grep -w \"author\" /vagrant/test.json |tail -1 | cut -d\" -f4 | |
| $ FOOBAZ="tester" | |
| $ jq -n --arg foobaz "$FOOBAZ" '{"foobaz":$foobaz}' > test1.json | |
| $ cat test1.json | |
| export $(jq -r '@sh "FOO=\(.foo) BAZ=\(.baz)"') #fill environment variables from JSON object keys (e.g. $FOO from jq query ".foo") | |
| echo '{ "foo": 123, "bar": 456 }' | jq '.foo' #print out the foo property | |
| apod_url=$(curl -s https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY | jq -r '.hdurl') #get the URL of the current Astronomy Picture of the Day (APOD) | |
| echo '{ "Version Number": "1.2.3" }' | jq '."Version Number"' #if a property has a spaces or weird characters | |
| echo '[1,2,3]' | jq '.[]' #how iteration works | |
| echo '[ {"id": 1}, {"id": 2} ]' | jq '.[].id' #access a property on each item | |
| echo '{ "a": 1, "b": 2 }' | jq '.[]' #the value of each key/value pair | |
| ---------------------------------------------------------------------------------------------------- | |
| bootstrap.sh | |
| parted /dev/sdb mklabel msdos | |
| parted /dev/sdb mkpart primary 512 100% | |
| mkfs.xfs /dev/sdb1 | |
| mkdir /mnt/disk | |
| mount /mnt/disk | |
| # Format the /dev/sdb partition with XFS filesystem and with a GPT partition table | |
| sudo parted -s /dev/sdb mklabel gpt mkpart primary xfs | |
| sudo mkfs.xfs /dev/sdb -f | |
| sudo blkid -o value -s TYPE /dev/sdb | |
| # list disk UUIDs | |
| ls -l /dev/disk/by-id | |
| $ fdisk -v | |
| $ sudo fdisk -l | |
| $ sudo fdisk -l /dev/sda1 | |
| ----------------------------------------------------------------------------------------------------- | |
| cut -c3 -> print the character from each 3rd line as a new line of output. | |
| cut -c2,7 -> Display the 2nd and 7th character from each line of text | |
| cut -c-4 -> Display the first four characters from each line of text | |
| cut -c13- -> Print the characters from thirteenth position to the end. | |
| cut -d' ' -f4 -> Given a sentence, identify and display its fourth word. Assume that the space (' ') is the only delimiter between words. | |
| cut -d' ' -f1-3 -> Given a sentence, identify and display its first three words. Assume that the space (' ') is the only delimiter between words. | |
| cut -f 1-3 -> Given a tab delimited file with several columns (tsv format) print the first three fields. | |
| cut -f2- -> Given a tab delimited file with several columns (tsv format) print the fields from second fields to last field. | |
| ----------------------------------------------------------------------------------------------------- | |
| uniq -ci -> count the number of times each line repeats itself (only consider consecutive repetions).compare consecutive lines in a case insensitive manner | |
| uniq -u -> display only those lines which are not followed or preceded by identical replications | |
| Given a text file, count the number of times each line repeats itself (only consider consecutive repetions). | |
| Display the count and the line, separated by a space. | |
| uniq -ci | cut -c7- | |
| ----------------------------------------------------------------------------------------------------- | |
| head -v -n 3 file1 # list the names of the files before outputting their content to the terminal | |
| head -n2 -q file1 file2 #Use the -n option to print the first n lines from a file | |
| head -n 20 -> Display the first lines of an input file. | |
| head -n-2 example.txt # skips the last 2 lines and prints the remaining lines. | |
| head -n10 filename | tail -5 #prints the lines between numbers 5 and 10 | |
| head -c5 example.txt #prints the first 5 bytes from the file. | |
| head -c-7 example.txt #skip printing last 7 bytes. | |
| head -c20 -> Display the first characters of an input file. | |
| head -n 22 | tail -n +12 -> Display the lines (from line number 12 to 22, both inclusive) of a given text file | |
| # print the lines between 5 and 10, both inclusive | |
| cat filename | head | tail -6 | |
| ----------------------------------------------------------------------------------------------------- | |
| tail -n 20 | tail -n +12 -> Display the last lines of an input file. | |
| tail -c 20 -> Display the last characters of an input file | |
| ----------------------------------------------------------------------------------------------------- | |
| echo BigcapsSmallCaps | tr [:lower:] [:upper:] # convert string into lower case, capital case etc | |
| tr '()' '[]' -> In a given fragment of text, replace all parentheses with box brackets | |
| tr -d [:lower:] -> In a given fragment of text, delete all the lowercase characters | |
| tr -d "[:space:]" < raw_file.txt #remove all whitespace characters from the file | |
| echo -e " \t A \tB\tC \t " | tr -d "[:blank:]" #deletes any space or tabulation character | |
| tr -s ' ' -> In a given fragment of text, replace all sequences of multiple spaces with just one space | |
| distribution=$(lsb_release --id | cut -f2 | tr [:upper:] [:lower:]) #all big caps to small caps | |
| ----------------------------------------------------------------------------------------------------- | |
| sort -> Given a text file, order the lines in lexicographical order. | |
| sort -r -> Given a text file, order the lines in reverse lexicographical order | |
| sort -n -> the lines reordered in numerically ascending order | |
| sort -nr -> The text file, with lines re-ordered in descending order (numerically). | |
| given a file of text,in TSV (tab-separated) format.Rearrange the rows of the table in descending order of the values | |
| sort -t$'\t' -rnk2 | |
| given a file of tab separated weather data (TSV). There is no header column in this data file.Sort the data in ascending order | |
| sort -nk2 -t$'\t' | |
| given a file of pipe-delimited weather data (TSV). There is no header column in this data file. | |
| sort -nrk2 -t$'|' | |
| ----------------------------------------------------------------------------------------------------- | |
| paste -s -> Given a CSV file where each row contains the name of a city and its state separated by a comma.replace the newlines in the file with tabs | |
| paste - - - -> given a CSV file where each row contains the name of a city and its state separated by a comma, restructure the file in such a way, that three consecutive rows are folded into one, and separated by tab. | |
| paste -s -d ";" -> given a CSV file where each row contains the name of a city and its state separated by a comma.replace the newlines in the file with semicolon | |
| paste - - - -d ";" -> given a CSV file where each row contains the name of a city and its state separated by a comma. restructure the file so that three consecutive rows are folded into one line and are separated by semicolons | |
| ----------------------------------------------------------------------------------------------------- | |
| #Detect exploitation attempts of the vulnerability in uncompressed files in the Linux logs directory /var/log and all its subdirectories | |
| egrep -I -i -r '\$(\{|%7B)jndi:(ldap[s]?|rmi|dns|nis|iiop|corba|nds|http):/[^\n]+' /var/log | |
| find /var/log/ -type f -exec sh -c "cat {} | sed -e 's/\${lower://'g | tr -d '}' | egrep -I -i 'jndi:(ldap[s]?|rmi|dns|nis|iiop|corba|nds|http):'" \; | |
| find /var/log/ -name '*.gz' -type f -exec sh -c "zcat {} | sed -e 's/\${lower://'g | tr -d '}' | egrep -i 'jndi:(ldap[s]?|rmi|dns|nis|iiop|corba|nds|http):'" \; | |
| #searches for exploitation attempts in compressed files in folder /var/log and all sub folders | |
| find /var/log -name \*.gz -print0 | xargs -0 zgrep -E -i '\$(\{|%7B)jndi:(ldap[s]?|rmi|dns|nis|iiop|corba|nds|http):/[^\n]+' | |
| #files starting at the current directory (.) and that up to a maximum of 1 level of subdirectories | |
| find . -maxdepth 2 -type f -name file.txt | xargs -I{} cat {} > ./total_file.txt | |
| #Get total size of a list of files | |
| perl -le 'map { $sum += -s } @ARGV; print $sum' -- *.pdf #Size of all non-hidden PDF files in current directory. | |
| #list files between 1st Dec 2021 and 1st Jan 2022 and total size of each file | |
| find . -type f -newermt 2012-01-01 ! -newermt 2022-01-01 -exec du -sh {} \; | |
| find . -type f -newermt 2012-01-01 ! -newermt 2022-01-01 -exec ls -lt {} \; | sort -k6M -k7n #sorting month & date based | |
| find . -name 'flibble*' -ctime +90 -exec du -sh {} \; | |
| find . -type f -mmin -5 -print0 | xargs -0 /bin/ls -ltr #which files was modified in last 5 minutes | |
| find . -type f -mmin -5 -exec ls -ltr {} + | |
| find . -mmin -5 -exec ls -ltrd {} + #not limiting to files | |
| #list files between 1st Dec 2021 and 1st Jan 2022 and grand total size of each found files, not sum of total sizes | |
| "find . -name "*.tar" -type f -newermt 2012-01-01 ! -newermt 2022-01-01 -exec du -sch {} +" | |
| find . "*.tar" -type f -newermt 2012-01-01 ! -newermt 2022-01-01 -exec du -sch {} + | tail -1 #only total | |
| find . -name "*.tar" -type f -newermt 2012-01-01 ! -newermt 2022-01-01 -exec du -sch {} + | tail -1 | awk '{print $1}' | |
| $ find . -size +2G #search for all files greater than 2 Gigabytes | |
| $ find . -size -10k #search for all files with less than 10 Kilobytes | |
| $ find . -size +10M -size -20M #search for files greater than 10MB but smaller than 20MB | |
| $ sudo find /var -size +5M -exec ls -sh {} + #search for files in /etc directory which are greater than 5MB and print file size | |
| $ find . -type f -exec ls -s {} + | sort -n -r | head -3 #Find first 3 largest files located in a in a current directory recursively | |
| $ find /etc/ -type f -exec ls -s {} + | sort -n | head -3 #Find first 3 smallest files located in a in a current directory recursively | |
| $ find . -type f -size 0b # search for empty files | |
| $ find . -type f -empty # search for empty files | |
| $ sudo find /var/log -name \*.log -size +1M -exec ls -lrt {} \; # find files larger than 1M,`M' for Megabytes (units of 1048576 bytes) | |
| $ sudo find /var/log -name \*.log -size +1M -exec ls -lrt {} \; | wc -l #get count | |
| $ sudo find /var/log -name \*.log -size +1M -exec ls -lrt {} \; | awk '{ total += $5 }; END { print total }' # get total size, column 5(size) of ls command, | |
| #total size of all found files | |
| $ sudo find /var/log -name \*.log -size +1M -exec ls -l {} \; | awk '{ sum += $5} END \ | |
| {hum[1024^3]="Gb"; hum[1024^2]="Mb"; hum[1024]="Kb"; for (x=1024^3; x>=1024; x/=1024) { if (sum>=x) { printf "%.2f %s\n",sum/x,hum[x]; break; } } if (sum<1024) print "1kb"; }' | |
| $ find /var/log/apt -type f -name "*.dat" -size +100M #list files larger than 100M | |
| $ find /var/log/apt -iname *.log -print0 | xargs -r0 du -csh | tail -n 1; # -iname case insensitive | |
| $ find /var/log/apt -iname *.log -exec ls -lh {} \; | |
| $ find /var/log/apt -name *.log -size +10c -print0 | du -c --files0-from=- | awk 'END{print $1}' | |
| $ find /var/log/apt -name *.log -size +10c -print0 | du -ch --files0-from=- | awk 'END{print $1}' | |
| $ find /var/log/apt -name *.log -size +10c -print0 | du -ch --files0-from=- --total -s|tail -1 #xargs pipe "|" calls du command many times | |
| $ find /var/log/apt -name *.log -type f -exec ls -s \; | awk '{sum+=$1;} END {print sum/1000;}' #excludes all directories | |
| du -ch /var/log/apt | tail -1 | cut -f 1 | |
| $ (find /var/log/apt -name *.log -size +10c -printf '%s+'; echo 0 ) | bc | |
| $ ( find /var/log/apt -name *.log -size +10c -printf 's+=%s\n'; echo s ) | bc | |
| $ find /var/log/apt -name *.log -size +10c -printf '%s\n' | jq -s add | |
| $ find /var/log/apt -name *.log -size +10c -exec stat -c%s '{}' + | jq -s add | |
| find . -name "*.tar" -type f -newermt 2012-01-01 ! -newermt 2022-01-01 -print0 | xargs -0 du -c --block-size=human-readable | |
| find . -name 'flibble*' -ctime +90 -print0 > filenames && du -shc --files0-from=filenames | |
| du -c `find . -name 'flibble*' -ctime +90` | tail -1 | |
| find . -name 'flibble*' -ctime +90 -printf "%s\n" |perl -lnE '$sum += $_} END {say $sum' | |
| find . -name 'flibble*' -ctime +90 -printf "%s\t%p\n" |perl -apE '$sum += $F[0]} END {say $sum' | |
| echo "$(( ($(find . -name 'flibble*' -ctime +90 -type f -printf '%k+' )0)/1024/1024 )) GB" | |
| #-mtime +7 means older than 8 days (age rounded to integer number of days greater than 7). | |
| log_history=13 && find /opt/freeswitch/var/log/freeswitch -type f -mtime +$log_history -delete #Delete old/rotated log files | |
| # if tomcat directory exists,delete logs | |
| log_history=13 && [[ -d /var/log/tomcat7 ]] && find /var/log/tomcat7 -type f -mtime +$log_history -delete | |
| #Delete FreeSWITCH wav/opus recordings older than 13 days | |
| history=13 && find /var/freeswitch/meetings/ -name "*.wav" -mtime +$history -delete | |
| # find all files, SUID bit enabled | |
| find / -perm -4000 -exec ls -l {} \; | |
| find /usr/bin/ -perm -4000 -exec ls -l {} \; | |
| find /bin/ -perm -4000 -exec ls -l {} \; | |
| find / -xdev -perm -4000 2>/dev/null | |
| #-perm denotes that we will search for the permissions that follow: | |
| #-u=s denotes that we will look for files which are owned by the root user | |
| #-type states the type of file we are looking for | |
| #f denotes a regular file, excluding directories and special files | |
| find / -perm -u=s -type f 2>/dev/null | |
| find / -uid 0 –perm -4000 -print #find all programs whose SetUID is set to run as root | |
| find / -perm -2000 -exec ls -l {} \; # find all files, SGID bit enabled | |
| find /lib/modules/`uname -r` -type f -name '*quota_v*.ko*' | |
| find -type f -exec md5sum -t {} \; | cut -d ' ' -f 1 | sort | md5sum #compute checksum | |
| find . -type f -newermt 2012-02-01 ! -newermt 2022-01-01 #between 1st Dec 2021 and 1st Jan 2022 | |
| find . -type f -newermt 2012-02-01 ! -newermt 2022-01-01 -ls #list files between 1st Dec 2021 and 1st Jan 2022 | |
| find . -type f -newermt 2012-02-01 ! -newermt 2022-01-01 -exec echo {} \; #test before delete | |
| find . -type f -newermt 2012-02-01 ! -newermt 2022-01-01 -exec rm -rf {} \; #delete between 1st Dec 2021 and 1st Jan 2022 | |
| find . -type f -newermt 2012-01-01 ! -newermt 2022-01-01 -exec ls -l {} \; | |
| #never put the -delete action at the first position | |
| #If the -delete action is at the first position, during its evaluation, it deletes the given directory and everything in it | |
| #the -delete action implies the -depth option | |
| #The -depth option asks the find command to search each directory’s contents before the directory itself. | |
| # -delete as the first option, it starts deletion from each directory tree’s very bottom | |
| $ find test -delete -type d -name '.git' # the test directory has been deleted | |
| $ ls test | |
| ls: cannot access 'test': No such file or directory | |
| #the -delete action cannot delete a non-empty directory recursively, can only delete files and empty directories | |
| find test -depth -type d -name '.git' -exec rm -r '{}' \; #remove all .git directories | |
| find test -type d -name '.git' | xargs rm -r #remove all .git directories | |
| find ~/Downloads/ -empty -type d -delete #delete all empty directories | |
| find /path/ -empty -type d | wc -l ## count empty dirs only ## | |
| find /path/to/dir/ -type d -empty -print0 | xargs -0 -I {} /bin/rmdir "{}" #find and delete all empty directories | |
| find /path/to/dir -type d -empty -print0 -exec rmdir -v "{}" \; #find and delete all empty directories,slow due to -exec | |
| $ sudo find /var -type d -empty -mtime +50 | |
| $ sudo find /var -type d -empty -mtime +5 -exec sh -c 'du -sch' sh {} + | |
| #-exec with an external command, it fills each found file in the ‘{}’ placeholder | |
| find test -name 'whatever.txt' -exec rm {} \; #remove all whatever.txt files | |
| find test -name 'whatever.txt' | xargs rm #remove all whatever.txt files | |
| find ~/Downloads/ -empty -type -f -delete #delete all empty files | |
| find /path/ -empty -type f | wc -l ## count empty files only ## | |
| find /path/to/dir/ -type f -empty -print0 | xargs -0 -I {} /bin/rm "{}" #delete all empty files | |
| find /path/to/dir/ -type f -empty -print0 -exec rm -v "{}" \; #delete all empty files,slow due to -exec | |
| find / -name .DS_Store -delete #-delete will perform better because it doesn't have to spawn an external process for each and every matched file | |
| find / -name ".DS_Store" -exec rm {} \; #recommended because -delete does not exist in all versions of find | |
| find / -iname "*~" -exec rm -i {} \; # gives an interactive delete | |
| find / -name .DS_Store -exec rm {} + #The command termination + instead of \; highly optimizes the exec clause by not running the rm command for each and every .DS_Store present on the file system | |
| find / -name .DS_Store -print0 | xargs -0 rm #avoiding the overhead of spawning an external process for each matched file | |
| find . -type f -newermt 2012-01-01 ! -newermt 2022-01-01 -exec du -sh {} \;#list files between 1st Dec 2021 and 1st Jan 2022 and total size | |
| #-delete does not delete empty directories | |
| $ find /path/to/dir/ -type d -name ".TemporaryItems" -delete | |
| find: cannot delete ‘./.TemporaryItems’: Directory not empty | |
| $ find /path/to/dir/ -type d -name ".TemporaryItems" -exec rm -rv "{}" + | |
| find test -type d -name '.git' # list git directories | |
| find . -type d -newermt 2012-02-01 ! -newermt 2022-01-01 -ls #list directories between 1st Dec 2021 and 1st Jan 2022 | |
| find . -type d -newermt 2012-03-22 ! -newermt 2022-03-24 -exec echo {} \; #test before delete | |
| find . -type d -newermt 2012-02-01 ! -newermt 2022-01-01 -exec rm -rf {} \; #delete directories between 1st Dec 2021 and 1st Jan 2022 | |
| find /dir/ -type f -newerXY 'yyyy-mm-dd' | |
| The letters X and Y can be any of the following letters: | |
| a – The access time of the file reference | |
| B – The birth time of the file reference | |
| c – The inode status change time of reference | |
| m – The modification time of the file reference | |
| t – reference is interpreted directly as a time | |
| find . -type f -newerat 2017-09-25 ! -newerat 2017-09-26 #all files accessed on the 25/Sep/2017 | |
| find /home/you -iname "*.c" -atime 30 -type f #all *.c file accessed exactly 30 days ago | |
| find /home/you -iname "*.c" -atime -30 -type f #all *.c file accessed 30 days ago, not older than 30 days | |
| find /home/you -iname "*.c" -atime -30 -type f -ls | |
| find /home/you -iname "*.c" -atime +30 -type f #all *.c file accessed more than 30 days ago, older than 30 days | |
| find /home/you -iname "*.c" -atime +30 -type f -ls | |
| ----------------------------------------------------------------------------------------------------- | |
| #Users of the bash shell need to use an explicit path in order to run the external time command and | |
| #not the shell builtin variant. On systemwhere time is installed in /usr/bin, | |
| #Real is wall clock time - time from start to finish of the call. This is all elapsed time including | |
| #time slices used by other processes and time the process spends blocked (for example if it is waiting for I/O to complete). | |
| #User is the amount of CPU time spent in user-mode code (outside the kernel) within the process. | |
| #This is only actual CPU time used in executing the process. Other processes and time the process | |
| #spends blocked do not count towards this figure. | |
| #Sys is the amount of CPU time spent in the kernel within the process. This means executing CPU time | |
| #spent in system calls within the kernel, as opposed to library code, which is still running in user-space | |
| $ /usr/bin/time -o out.txt sudo find /var/log -name '*log' -ctime +1 -exec du -sh {} \; | |
| $ cat out.txt | |
| 0.01user 0.03system 0:00.06elapsed 76%CPU (0avgtext+0avgdata 8756maxresident)k | |
| 0inputs+0outputs (0major+2771minor)pagefaults 0swaps | |
| #the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end | |
| $ /usr/bin/time -o outplus.txt sudo find /var/log -name '*log' -ctime +1 -exec du -sh {} +; | |
| $ cat outplus.txt | |
| 0.00user 0.01system 0:00.02elapsed 73%CPU (0avgtext+0avgdata 8804maxresident)k | |
| 0inputs+0outputs (0major+1091minor)pagefaults 0swaps | |
| $ /usr/bin/time -o out.txt sudo find /var/log -name '*log' -ctime +1 -exec du -sh {} \; | |
| $ /usr/bin/time -f "\t%C [Command details],\t%K [Total memory usage],\t%k [Number of signals process received]" ping -c 2 howtoforge.com | |
| ----------------------------------------------------------------------------------------------------- | |
| # displays without comments | |
| egrep -v "^#|^$" /etc/zabbix/zabbix_server.conf | |
| ----------------------------------------------------------------------------------------------------- | |
| #r = recursive i.e, search subdirectories within the current directory | |
| #n = to print the line numbers to stdout | |
| #i = case insensitive search | |
| grep -rni "string" * | |
| grep -rni "apache /etc/cron.d" | |
| #string search current and subfolders | |
| $ grep -rl "900990" . | |
| ./.crs-setup.conf.swp | |
| ./crs/crs-setup.conf | |
| ./crs-setup.conf | |
| # displays the comments | |
| grep ^# /etc/resolv.conf | |
| # displays without comments | |
| grep ^[^#] /etc/resolv.confprint directory/file structure in the form of a tree | |
| grep ^[^\;] /etc/resolv.conffind . | sed -e "s/[^-][^\/]*\// |/g" -e "s/|\([^ ]\)/|-\1/" | |
| grep -v "^#" /etc/zabbix/zabbix_server.conf | grep -v "^$"sed '' quote.txt -> display the contents of the file | |
| # search multiple strings, words | |
| grep 'string1' filename | grep 'string2' #search two strings in one line | |
| grep -n 'string1' filename | grep 'string2' #search two strings in one line and print line numbers | |
| grep 'string1.*string2\|string2.*string1' filename #search two strings in one line | |
| grep -n 'string1.*string2\|string2.*string1' filename #search two strings in one line and print line numbers | |
| grep -E "string1(?.*)string2" file #search two strings in one line | |
| grep -nE "string1(?.*)string2" file #search two strings in one line and print line numbers | |
| #Grep for Multiple Strings | |
| grep 'wordA*'\''wordB' *.py ### Search all python files for 'wordA' or 'wordB' | |
| grep 'word*' *.txt ### Search all text files | |
| grep 'word1\|word2\|word3' /path/to/file | |
| grep 'warning\|error\|critical' /var/log/messages | |
| grep -e 'warning\|error\|critical' /var/log/messages | |
| egrep -wi --color 'warning|error|critical' /var/log/messages #-i (ignore case) | |
| egrep -wi --color 'foo|bar' /etc/*.conf | |
| egrep -Rwi --color 'foo|bar' /etc/ #including sub-directories | |
| egrep -w 'warning|error|critical' /var/log/messages | |
| grep -w 'warning\|error\|critical' /var/log/messages | |
| egrep -ne 'null|three' #search multiple string and output line numbers | |
| grep -o "0x[^']*" file.txt # matching text starting with "0x" | |
| grep "zip$" #filters the lines that end in zip | |
| grep -r --include "*.jar" JndiLookup.class / #Detect the presence of Log4j | |
| grep --color regex filename #Highlight | |
| grep --color ksh /etc/shells | |
| grep -o regex filename #Only The Matches, Not The Lines | |
| egrep "v{2}" filename #Match a character “v” two times | |
| egrep 'co{1,2}l' filename #match both “col” and “cool” words | |
| egrep 'c{3,}' filename #match any row of at least three letters ‘c’ | |
| grep "[[:digit:]]\{2\}[ -]\?[[:digit:]]\{10\}" filename #match mobile number format 91-1234567890 | |
| egrep '[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.[[:digit:]]{1,3}\.[[:digit:]]{1,3}' file #match an IP address,All three dots need to be escaped | |
| $ grep '^[P-R]' list.txt #lines from list.txt file that starts with P or Q or R | |
| $ grep '[^A-C]' list.txt #lines from list.txt file that starts with A or B or C | |
| $ grep [!P-R] list.txt #from list.txt file that starts with ‘P’ or Q or R | |
| $ grep [!4-8] list.txt #lines from list.txt file that starts with any digit from 4 to 8. | |
| $ grep a$ list.txt #lines from list.txt file that ends with ‘a’ | |
| $ grep 50$ list.txt #lines from list.txt file that end with the number 50 | |
| grep -i "boar" /etc/passwd #Perform a case-insensitive search for the word ‘bar’ | |
| grep "Gnome Display Manager" /etc/passwd #If the search string includes spaces, enclose it in single or double quotation marks | |
| #the string “linux” will match only if it occurs at the very beginning of a line | |
| grep '^linux' file.txt #The ^ (caret) symbol | |
| grep 'linux$' file.txt #lines end with linux string | |
| grep '^linux$' file.txt #lines contain only linux string | |
| grep '^\.[0-9]' filename #lines starting with a dot and digit | |
| grep '^..$' filename #lines with two characters | |
| #The . (period) symbol is a meta-character that matches any single character | |
| grep 'kan..roo' file.txt #match anything that begins with “kan” then has two characters and ends with the string “roo” | |
| grep 'acce[np]t' file.txt #find the lines that contain “accept” or “accent” | |
| grep 'co[^l]a' file.txt #match any combination of strings starting with “co” followed by any letter except “l” followed by “la”, such as “coca”, “cobalt” and so on | |
| grep '^[A-Z]' file.txt #matches each line that starts with a capital letter | |
| grep 's*right' #match “right”, “sright” “ssright” and so on | |
| grep -E '^[A-Z].*[.,]$' file.txt #matches all lines that starts with capital letter and ends with either period or comma | |
| grep 'b\?right' file.txt #match both “bright” and “right”. The ? character is escaped with a backslash because we’re using basic regular expressions | |
| grep -E 'b?right' file.txt | |
| grep -E 's+right' file.txt #match “sright” and “ssright”, but not “right” | |
| grep -E '[[:digit:]]{3,9}' file.txt #matches all integers that have between 3 and 9 digits | |
| grep 'word' filename | |
| grep 'word' file1 file2 file3 | |
| grep -i "boar" /etc/passwd #Perform a case-insensitive search for the word ‘bar’ | |
| "grep -R 'httpd' ." #Look for all files in the current directory and in all of its subdirectories | |
| grep -r "192.168.1.5" /etc/ #search recursively i.e. read all files under each directory for a string “192.168.1.5” | |
| grep -c 'nixcraft' frontpage.md #display the total number of times that the string ‘nixcraft’ appears in a file named frontpage.md | |
| #Grep NOT | |
| #-v flag to print inverts the match; that is, it matches only those lines that do not contain the given word | |
| grep -v -c -e "that" -> find out how many lines that does not match the pattern | |
| grep -v Sales employee.txt #all the lines except those that contains the keyword “Sales” | |
| grep -w "the" -> Output only those lines that contain the word 'the'. | |
| grep -iw "the" -> Output only those lines that contain the word 'the'. The search should NOT be case sensitive. | |
| grep -viwe "that" -> Only display those lines that do NOT contain the word 'that'. | |
| grep -Eiw "th(e|ose|en|at)" < /dev/stdin -> display all those lines which contain any of the following words "the,that,then,those" .The search should not be sensitive to case. Display only those lines of an input file, which contain the required words. | |
| grep '\([0-9]\) *\1' -> Given an input file, with N credit card numbers,grep out and output only those credit card numbers which have two or more consecutive occurences of the same digit (which may be separated by a space, if they are in different segments). Assume that the credit card numbers will have 4 space separated segments with 4 digits each | |
| #top 10 IP addresses in the log file. | |
| grep -E -o "([0-9]{1,3}[\.]){3}[0-9]{1,3}" access.log | uniq -ci | sort -nr | head -n10 | |
| ifconfig -a | grep -E -o "([0-9]{1,3}[\.]){3}[0-9]{1,3}" | awk 'ORS=NR%2?" , ":"\n"' | |
| ip addr show eth1 | grep inet | awk '{ print $2; }' | sed 's/\/.*$//' | |
| ifconfig -a | grep -E -o "([0-9]{1,3}[\.]){3}[0-9]{1,3}" | |
| #list process binary path and permissions | |
| ps aux | awk '{print $11}' | xargs -r ls -la 2>/dev/null |awk '!x[$0]++' | |
| ps -elf | grep autofs | grep -v grep | awk '{print $4}' | xargs kill -9 | |
| ######group expressions,grep -E option is for extended regexp,three expressions are functionally equivalent | |
| grep "\(grouping\)" file.txt #use parentheses without using extended regular expressions, escape with the backslash | |
| grep -E "(grouping)" file.txt | |
| egrep "(grouping)" file.txt | |
| grep -E "(GPL|General Public License)" GPL-3 #find either GPL or General Public License in the text | |
| grep -E "(copy)?right" GPL-3 #matches copyright and right by putting copy in an optional group | |
| grep -E '(fear)?less' file.txt #matches both “fearless” and “less”. The ? quantifier makes the (fear) group optional | |
| grep -E "free[^[:space:]]+" GPL-3 # matches the string free plus one or more characters that are not white space characters | |
| grep -E "[AEIOUaeiou]{3}" GPL-3 #find all of the lines in the GPL-3 file that contain triple-vowels | |
| grep -E "[[:alpha:]]{16,20}" GPL-3 #match any words that have between 16 and 20 characters | |
| grep -e pattern1 -e pattern2 filename #Grep OR Using grep -e, | |
| egrep 'Tech|Sales' employee.txt #Grep OR Using egrep | |
| grep 'Tech\|Sales' employee.txt #Grep OR Using \|,grep either Tech or Sales from the employee.txt file | |
| grep 'fatal\|error\|critical' /var/log/nginx/error.log | |
| grep -E 'fatal|error|critical' /var/log/nginx/error.log # use the extended regular expression, then the operator | should not be escaped | |
| grep -E 'Tech|Sales' employee.txt #Grep OR Using -E | |
| #Grep AND | |
| grep Manager employee.txt | grep Sales #all the lines that contain both “Manager” and “Sales” in the same line | |
| grep -E 'Dev.*Tech' employee.txt #all the lines that contain both “Dev” and “Tech” in it (in the same order). | |
| grep -E 'Manager.*Sales|Sales.*Manager' employee.txt #all the lines that contain both “Manager” and “Sales” in it (in any order) | |
| ----------------------------------------------------------------------------------------------------- | |
| user@host: $ cat<<EOF > file.txt | |
| $ > 1 line | |
| $ > other line | |
| $ > n line | |
| $ > EOF | |
| user@host: | |
| ----------------------------------------------------------------------------------------------------- | |
| # append text | |
| cat<<EOF | sudo tee -a ceph.conf | |
| public network = 192.168.18.0/24 | |
| osd pool default size = 2 | |
| EOF | |
| ----------------------------------------------------------------------------------------------------- | |
| sudo install consul /usr/bin/consul | |
| ( | |
| cat <<-EOF | |
| [Unit] | |
| Description=consul agent | |
| Requires=network-online.target | |
| After=network-online.target | |
| [Service] | |
| Restart=on-failure | |
| ExecStart=/usr/bin/consul agent -dev | |
| ExecReload=/bin/kill -HUP $MAINPID | |
| [Install] | |
| WantedBy=multi-user.target | |
| EOF | |
| ) | sudo tee /etc/systemd/system/consul.service | |
| ----------------------------------------------------------------------------------------------------- | |
| cat <<EOT | sudo tee /lib/systemd/system/procenv.service | |
| [Unit] | |
| Description=Display systemd environment | |
| [Service] | |
| Type=oneshot | |
| ExecStart=/usr/bin/procenv --file=/tmp/procenv-systemd.log | |
| EOT | |
| ----------------------------------------------------------------------------------------------------- | |
| > outputs to a file | |
| >> appends to a file | |
| < reads input | |
| <<Here tells the shell that you are going to enter a multiline string until the "tag" Here. You can name this tag as you want, it's often EOF or STOP. | |
| "EOF" is known as a "Here Tag" | |
| The redirection operators "<<" and "<<-" both allow redirection of lines contained in a shell input file, | |
| known as a "here-document", to the input of a command. | |
| The format of here-documents is: | |
| <<[-]word | |
| here-document | |
| delimiter | |
| If the redirection operator is <<-, then all leading tab characters are stripped from input lines and the line containing delimiter. | |
| This allows here-documents within shell scripts to be indented in a natural fashion. | |
| ----------------------------------------------------------------------------------------------------- | |
| # Assign multi-line string to a shell variable | |
| # The $sql variable now holds the new-line characters | |
| # verify with echo -e "$sql" | |
| sql=$(cat <<EOF | |
| SELECT foo, bar FROM db | |
| WHERE foo='baz' | |
| EOF | |
| ) | |
| ----------------------------------------------------------------------------------------------------- | |
| #Pass multi-line string to a file in Bash | |
| $ cat <<EOF > print.sh | |
| #!/bin/bash | |
| echo \$PWD | |
| echo $PWD | |
| EOF | |
| ----------------------------------------------------------------------------------------------------- | |
| # Pass multi-line string to a pipe in Bash | |
| $ cat <<EOF | grep 'b' | tee b.txt | |
| foo | |
| bar | |
| baz | |
| EOF | |
| ----------------------------------------------------------------------------------------------------- | |
| $ sudo tee <<EOF /etc/somedir/foo.conf >/dev/null | |
| # my config file | |
| foo=bar | |
| EOF | |
| ----------------------------------------------------------------------------------------------------- | |
| echo -e " | |
| Home Directory: $HOME \n | |
| hello world 1 \n | |
| hello world 2 \n | |
| line n... \n | |
| " > file.txt | |
| ----------------------------------------------------------------------------------------------------- | |
| echo write something to file.txt | cat > file.txt | |
| cat >file.txt <<< Write something here | |
| # see the line numbers | |
| cat -n song.txt | |
| # shows at the end of line and also in space showing ‘$‘ if there is any gap between paragraphs | |
| # useful to squeeze multiple lines in a single line. | |
| cat -e test | |
| # all output will be redirected in a newly created file | |
| cat test test1 test2 > test3 | |
| # Sorting Contents of Multiple Files in a Single File | |
| cat test test1 test2 test3 | sort > test4 | |
| # Display Multiple Files at Once | |
| cat test; cat test1; cat test2 | |
| # append your text to the end of the file | |
| cat >> ~/.bashrc <<EOF | |
| # my config file | |
| foo=bar | |
| EOF | |
| cat > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor <<EOF | |
| performance | |
| EOF | |
| ----------------------------------------------------------------------------------------------------- | |
| curl -sSL https://releases.hashicorp.com/nomad/${NOMAD_VERSION}/nomad_${NOMAD_VERSION}_linux_amd64.zip -o nomad.zip | |
| https://releases.hashicorp.com/packer/${PACKER_VERSION}/packer_${PACKER_VERSION}_linux_amd64.zip | |
| curl -sSL https://releases.hashicorp.com/vagrant/${VAGRANT_VERSION}/vagrant_${VAGRANT_VERSION}_linux_amd64.zip -o vagrant.zip | |
| curl -sSL https://releases.hashicorp.com/vagrant/2.2.2/vagrant_2.2.2_linux_amd64.zip -o vagrant.zip | |
| unzip vagrant.zip | |
| $ curl -L https://raw.githubusercontent.com/do-community/ansible-playbooks/master/docker/ubuntu1804.yml -o /vagrant/docker_ubuntu.yml | |
| export VER="4.4.6" | |
| "curl -SL https://github.com/NagiosEnterprises/nagioscore/releases/download/nagios-$VER/nagios-$VER.tar.gz | tar -xzf -" | |
| cd nagios-$VER | |
| ------------------------------------------------------------------------------------------ | |
| tar -C /usr/local -xzf go1.19.linux-amd64.tar.gz # extract the archive into /usr/local, creating a fresh Go tree in /usr/local/go | |
| ------------------------------------------------------------------------------------------ | |
| split --bytes=2048m WinXP.img WinXP_img_ | |
| # four files (2GB each) appeared | |
| WinXP_img_aa | |
| WinXP_img_ab | |
| WinXP_img_ac | |
| WinXP_img_ad | |
| cat WinXP_img_* > WinXP.img | |
| # join smaller files into a larger one | |
| cat partfilename* > outputfilename | |
| video.avi.01 | |
| video.avi.02 | |
| video.avi.03 | |
| cat video.avi.* > video1.avi | |
| $ cat file1 | |
| 1. Asia: | |
| 2. Africa: | |
| 3. Europe: | |
| 4. North America: | |
| tac tacexample.txt #print files in reverse | |
| $ tac file1 | |
| 4. North America: | |
| 3. Europe: | |
| 2. Africa: | |
| 1. Asia: | |
| $ cat file2 | |
| 1. India | |
| 2. Nigeria | |
| 3. The Netherlands | |
| 4. The US | |
| $ join file1 file2 | |
| 1. Asia: India | |
| 2. Africa: Nigeria | |
| 3. Europe: The Netherlands | |
| 4. North America: The US | |
| join -1 1 -2 1 -e 'empty' /tmp/in /tmp/out | tr " " "\t" #join the two files,the first column in each file as index | |
| # create a new file “new.txt” that is a concatenation of “file1.txt” and “file2.txt” | |
| cat file1.txt file2.txt > new.txt | |
| format text and convert it to a different width | |
| $ fmt --width=20 test.txt | |
| ------------------------------------------------------------------------------------------ | |
| g++ -v | |
| g++ temp.cpp | |
| # run | |
| ./a.out | |
| ------------------------------------------------------------------------------------------ | |
| # Installing software from source | |
| tar xvzf package.tar.gz | |
| tar xvjf package.tar.bz2 | |
| cd package | |
| ./configure | |
| make | |
| make install | |
| # Cleaning up | |
| make clean | |
| make uninstall | |
| # "make clean" runs as expected even if you do have a file named clean. | |
| # There are two reasons to use a phony target: to avoid a conflict with a file of the same name, and to improve performance. | |
| .PHONY: clean | |
| clean: | |
| rm -rf *.o | |
| # case1 | |
| $ cat make | |
| hello : hello.o | |
| gcc -Wall hello.o -o hello | |
| $ cat hello.c | |
| #include<stdio.h> | |
| int main(void) | |
| { | |
| printf("\n Hello World!!!\n"); | |
| return 0; | |
| } | |
| $ cp make mon-makefile | |
| $ ls | |
| hello.c make mon-makefile | |
| make -C makefile-test1/ hello | |
| make -f mon-makefile | |
| make -s | |
| # case2 | |
| $ cat file2.h | |
| void add(int a, int b, void (*f)(int)); | |
| $ cat file2.c | |
| #include<stdio.h> | |
| #include"file2.h" | |
| void add(int a, int b, void(*f)(int)) | |
| { | |
| int c = a+b; | |
| f(c); | |
| } | |
| $ cat file1.c | |
| #include<stdio.h> | |
| #include"file2.h" | |
| void callback (int result) | |
| { | |
| printf("\n Result is : [%d] \n", result); | |
| } | |
| int main(void) | |
| { | |
| int a=0,b=0; | |
| printf("\n Enter two numbers to add: "); | |
| scanf("%d %d",&a, &b); | |
| add(a,b,callback); | |
| return 0; | |
| } | |
| $ cat makefile | |
| file : file1.o file2.o | |
| gcc -Wall file2.o file1.o -o file | |
| file1.o : file1.c file2.h | |
| gcc -c -Wall file1.c -o file1.o | |
| file2.o : file2.c file2.h | |
| gcc -c -Wall file2.c -o file2.o | |
| $ cp make mon-makefile | |
| $ ls | |
| file1.c file2.c file2.h makefile mon_makefile | |
| ------------------------------------------------------------------------------------------ | |
| # linux system management | |
| top | |
| sar | |
| vmstat | |
| iostat | |
| free | |
| ps | |
| tcpdump | |
| iptraf | |
| nestat | |
| # /Proc file system - Various Kernel Statistics | |
| cat /proc/cpuinfo | |
| cat /proc/meminfo | |
| cat /proc/zoneinfo | |
| cat /proc/mounts | |
| ------------------------- ----------------------------------------------------------------- | |
| $ uptime | |
| #"system load averages" that show the running thread (task) demand on the system as an average number of running plus waiting threads. | |
| #show three averages, for 1, 5, and 15 minutes | |
| #If the averages are 0.0, system is idle | |
| #If the 1 minute average is higher than the 5 or 15 minute averages, then load is increasing | |
| #If the 1 minute average is lower than the 5 or 15 minute averages, then load is decreasing. | |
| ps -eL h -o state | egrep "R|D" | wc -l #The instantaneous number of such tasks | |
| #Linux load average,the instantaneous load of a system the number of tasks (processes and threads) that are willing to run at a given time t | |
| #either in state R or D, either actually running or blocked on some resource (CPU, IO, ...) waiting for an opportunity to run | |
| list user vagrant's full command line of processes | |
| $ top -c -u vagrant | |
| ignore idle processes | |
| $ top -i -u vagrant | |
| updated with 5 secs intervals, including child processes | |
| $ top -u vagrant -c -d 5 -S | |
| #determine which Plaso processes are running | |
| top -p `ps -ef | grep log2timeline.py | grep python | awk '{ print $2 }' | tr '\n' ',' | sed 's/,$//'` | |
| The load averages shown by these tools is read /proc/loadavg file | |
| cat /proc/loadavg | |
| ------------------------------------------------------------------------------------------ | |
| # same inodes | |
| ls -ldi /. /.. | |
| 2 drwxr-xr-x 24 root root 4096 Feb 21 20:28 /. | |
| 2 drwxr-xr-x 24 root root 4096 Feb 21 20:28 /.. | |
| # different inodes | |
| ls -ldi /home/vagrant/. /home/vagrant/.. | |
| 3145730 drwxr-xr-x 7 vagrant vagrant 4096 Feb 22 10:14 /home/vagrant/. | |
| 3145729 drwxr-xr-x 3 root root 4096 Aug 24 08:48 /home/vagrant/.. | |
| ------------------------------------------------------------------------------------------ | |
| # The user file-creation mode mask (umask) | |
| /etc/profile | |
| ~/.bashrc | |
| ~/.bash_profile | |
| # By default | |
| 0022 (022) | |
| 0002 (002) | |
| files | |
| 666 | |
| directories | |
| 777 | |
| The default umask 002 used for normal user | |
| directory permissions | |
| 775 | |
| file permissions | |
| 664 | |
| The default umask for the root user is 022 | |
| directory permissions | |
| 755 | |
| file permissions | |
| 644 | |
| base permissions | |
| directory permissions | |
| (rwxrwxrwx) 0777 | |
| file permissions | |
| (rw-rw-rw) 0666 | |
| # No other user can read or write your data | |
| umask 077 | |
| # when you share data with other users in the same group | |
| # Members of your group can create and modify data files | |
| # those outside your group can read data file, but cannot modify it. | |
| umask 022 | |
| # exclude users who are not group members | |
| umask 007 | |
| # The octal umasks are calculated via the bitwise AND of the unary complement of the argument using bitwise NOT | |
| Octal value : Permission | |
| 0 : read, write and execute | |
| 1 : read and write | |
| 2 : read and execute | |
| 3 : read only | |
| 4 : write and execute | |
| 5 : write only | |
| 6 : execute only | |
| 7 : no permissions | |
| ------------------------------------------------------------------------------------------ | |
| # testing webpages | |
| $ telnet control01 80 #test website availability and get the response code | |
| GET /index.html HTTP/1.1 | |
| Host: control01 | |
| GET /index.html HTTP/1.1 | |
| Host: control01 | |
| If-modified-since: Sun, 24 Feb 2019 12:59:37 GMT | |
| GET /telnet-send-get-head-http-request HTTP/1.1 | |
| HOST: control01 | |
| HEAD / HTTP/1.1 | |
| Host: control01 | |
| ------------------------------------------------------------------------------------------ | |
| # delete files containing special chars | |
| $ cat>>"-f"<<EOF | |
| > test | |
| > EOF | |
| $ ls | |
| -f test test2 videos | |
| $ ls -li | |
| total 260 | |
| 3145770 -rw-rw-r-- 1 vagrant vagrant 5 Mar 5 17:02 -f | |
| find / -name wget 2>/dev/null | |
| find /home/vagrant -name file1 | |
| find /home/vagrant -user root | |
| find /home/vagrant -group root | |
| find . -inum 3145770 -delete | |
| find . -inum 3145770 -exec rm -i {} \; | |
| ls -il {file-name} | |
| find . -inum [inode] -exec rm -i {} \; | |
| ------------------------------------------------------------------------------------------ | |
| # steganography, attaching a .rar file to a .jpg etc. | |
| cat pic.jpg file.rar > result.jpg | |
| ------------------------------------------------------------------------------------------ | |
| # view used IRQs | |
| cat /proc/interrupts | |
| #determine the IRQ number associated with the Ethernet driver | |
| $ grep enp0s3 /proc/interrupts | |
| 19: 24006 IO-APIC-fasteoi enp0s3 | |
| $ grep eth0 /proc/interrupts | |
| 19: 13247 IO-APIC 19-fasteoi eth0 | |
| # troubleshoot network card etc. hardware conflicts, what addresses are used or free, or move conflicting hardware to free resource | |
| # listing IRQs currently being used.not listed IRQs are considered free.used when devices alert CPU to take action | |
| cat /proc/interrupts | |
| # listing used DMA channel.when devicess access memory directly without going through CPU | |
| cat /proc/dma | |
| # listing I/O ports currently being used.any range not listed is free and can be used by other devices. | |
| # devices have unique I/O addresses | |
| cat /proc/ioports | |
| ------------------------------------------------------------------------------------------ | |
| # view default shell for each user | |
| $ cat /etc/passwd | |
| # There are seven fields in the /etc/passwd file | |
| # username, UID, GID, comment, home directory, command | |
| # add an asterisk at the beginning of the password field in the /etc/passwd file, that user will not be able to log in | |
| /etc/passwd | |
| /etc/adduser.conf #Set DHOME variable for new default home directory of users. | |
| # useradd tecmint | |
| # useradd -m tecmint #create user with default home dir | |
| # passwd tecmint | |
| create admin user | |
| sudo useradd vagrant -s /bin/bash -g sudo -m | |
| modify a existing user to admin user | |
| sudo usermod -aG sudo vagrant # add user to a group, add vagrant to sudo group | |
| create a user ‘anusha‘ with a home directory ‘/data/projects‘. | |
| # useradd -d /data/projects anusha | |
| create a user ‘navin‘ with custom userid ‘999‘. | |
| # useradd -u 999 navin | |
| add a user ‘tarunika‘ with a specific UID and GID | |
| # useradd -u 1000 -g 500 tarunika | |
| add a user ‘tecmint‘ into multiple groups like admins, webadmin and developer | |
| # useradd -G admins,webadmin,developers tecmint | |
| # id tarunika | |
| uid=995(tarunika) gid=1001(vboxadd) groups=1001(vboxadd) | |
| create a user ‘aparna‘ with account expiry date i.e. 27th April 2014 in YYYY-MM-DD | |
| useradd -e 2014-03-27 aparna | |
| useradd -r -d /opt/gvm -c "GVM User" -s /bin/bash gvm #Create a system account,subordinate uid/gid feature is disabled,mail directory is not created | |
| chage -l aparna #verify the age of account | |
| chage -d 0 user #Minimum number of days between password change | |
| make changes to "/etc/shadow" file as root user #Minimum number of days between password change | |
| chage -M 7 aparna # aparna account’s password must be changed at least once every seven days | |
| sudo useradd test-user-0 && sudo passwd -d test-user-0 #create user without password | |
| awk -F: '($2 == "") {print}' /etc/shadow # verify users without password | |
| passwd -l test-user-0 #Lock all empty password account | |
| cat /etc/passwd | cut -d : -f 1 | awk '{ system("sudo passwd -S " $0) }' #list locked users | |
| sudo passwd -S -a | grep " L " | cut -d " " -f1 #list locked users, ubuntu | |
| sudo passwd -S -a | cut -d " " -f1-2 | grep "L$" #list locked users, ubuntu | |
| passwd -l user1 #lock the password | |
| grep user1 /etc/shadow #two exclamation mark (!!) before the encrypted password which means that the password has been locked | |
| passwd -u user1 #unlock the password | |
| passwd -S user1 #see the lock status of the user | |
| #A user whose account has a "non-interactive shell" (/bin/false, /sbin/nologin) can't log in interactively | |
| #prevents SSH command execution if the user has SSH keys on the system | |
| #users can't get a shell prompt to run commands | |
| # users may be able to log in to do read/send email (via POP/IMAP & SMTP AUTH) | |
| #/etc/security/access.conf | |
| #service accounts often don't have a "proper" login shell, /usr/sbin/nologin as login shell (or /bin/false) | |
| #service accounts have user IDs in the low range, e.g. < 1000 or so. Except for UID 0 | |
| #service accounts are typically locked | |
| #not possible to login (for traditional /etc/passwd and /etc/shadow) | |
| #achieved by setting the password hash to arbitrary values such as * or x) | |
| useradd testuser --shell=/sbin/nologin | |
| usermod testuser -s /sbin/nologin | |
| usermod -s /sbin/nologin test4 #Disable User Account With nologin or false Shells | |
| usermod testuser -s /bin/false #exit as soon as the user logs in, and return exit status 0 (false),do not receive any kind of message like they would with /sbin/nologin | |
| adduser subversion --shell=/bin/false --no-create-home | |
| # directed to the /sbin/nologin shell and receive the following message This account is currently not available. | |
| usermod testuser -s /bin/bash #enable shell by setting a shell | |
| #list non-interactive shell users, service accounts, aka technical accounts | |
| $ awk -F: '{if( $7~"/sbin/nologin" || $7~"/bin/false") print "service account..:",$1,"shell..:" $7}' /etc/passwd | |
| #The users that have nologin defined as their default shell often have higher privileges,unable to log in directly | |
| #limit the damage that a breach of system could suffer | |
| /sbin/nologin #Limiting system's attack surface | |
| /bin/false | |
| set a account password expiry date i.e. 45 days on a user ‘tecmint’ | |
| # useradd -e 2014-04-27 -f 45 tecmint | |
| insert that user’s full name, Manis Khurana | |
| # useradd -c "Manis Khurana" mansi | |
| add a user ‘tecmint‘ without login shell | |
| # useradd -s /sbin/nologin tecmint | |
| create a user ‘ravi‘ with home directory ‘/var/www/tecmint‘, default shell /bin/bash and adds extra information about user | |
| # useradd -m -d /var/www/ravi -s /bin/bash -c "TecMint Owner" -U ravi | |
| # useradd -m -d /var/www/tarunika -s /bin/zsh -c "TecMint Technical Writer" -u 1000 -g 1000 tarunika | |
| disabling login shell to a user called ‘avishek‘ | |
| # useradd -m -d /var/www/avishek -s /usr/sbin/nologin -c "TecMint Sr. Technical Writer" -u 1019 avishek | |
| useradd librenms -d /opt/librenms -M -r -s "$(which bash)" | |
| tecmint:x:504:504:tecmint:/home/tecmint:/bin/bash | |
| Username: User login name used to login into system. It should be between 1 to 32 charcters long. | |
| Password: User password (or x character) stored in /etc/shadow file in encrypted format. | |
| User ID (UID): Every user must have a User ID (UID) User Identification Number. By default UID 0 is reserved for root user and UID’s ranging from 1-99 are reserved for other predefined accounts. Further UID’s ranging from 100-999 are reserved for system accounts and groups. | |
| Group ID (GID): The primary Group ID (GID) Group Identification Number stored in /etc/group file. | |
| User Info: This field is optional and allow you to define extra information about the user. For example, user full name. This field is filled by ‘finger’ command. | |
| Home Directory: The absolute location of user’s home directory. | |
| Shell: The absolute location of a user’s shell i.e. /bin/bash. | |
| userdel member2 # deletes the account but leaves the user’s home directory intact | |
| userdel -f member2 # the -f option forces account deletion and fle removal under some circumstances | |
| userdel -r member2 # delete user account member2, the -r option to userdel causes it to delete the user’s home directory and mail spoo | |
| usermod -L testuser # lock user account / disable user account | |
| cat /etc/shadow | grep testuser # verify locked user account, exclamation mark "!" | |
| sudo passwd -S testuser #verify locked user account | |
| passwd --status testuser #verify locked user account | |
| usermod -U member1 # unlock user account | |
| passwd -u user1 #unlock the password | |
| # configure user default shell | |
| usermod -s /bin/bash member1 | |
| # add the user geek to the group sudo | |
| usermod -a -G sudo geek | |
| useradd -ms /bin/bash newuser #creates a home directory for the user and ensures that bash is the default shell | |
| useradd -rm -d /home/ubuntu -s /bin/bash -g root -G sudo -u 1001 ubuntu | |
| ------------------------------------------------------------------------------------------ | |
| #use useradd instead of its interactive wrapper adduser | |
| # create new user, new group with the same name | |
| sudo adduser sdn --system --group | |
| make sure username is added to the group libvirtd | |
| $ sudo adduser `id -un` libvirtd | |
| $ sudo adduser $(id -un) libvirtd | |
| ------------------------------------------------------------------------------------------ | |
| #edit the managers entry in /etc/group to make sally, tom, and dale members of the group managers (GID 501),the | |
| #order of users in the comma-separated user list is unimportant | |
| managers:x:501:dale,sally,tom | |
| cat /etc/group | |
| cat /etc/gshadow | |
| cut -d: -f1 /etc/group | sort | |
| $ groupadd admins #add new group | |
| $ sudo groupdel sshusers | |
| $ useradd -G admins member1 | |
| sudo usermod -aG docker ${USER} #Add current logged in user to the docker group. | |
| sudo usermod -aG docker $(whoami) #Add current logged in user to the docker group. | |
| gpasswd -a devops1 sudo #Adding user devops1 to group sudo | |
| gpasswd -d devops1 sudo #Removing user devops1 from group sudo | |
| #list groups on Linux,/etc/group file | |
| $ getent group | |
| $ getent group sudo # sudo group has ID of 27 and has ubuntu,barak,packer as members | |
| sudo:x:27:ubuntu,barak,packer | |
| $ cat /etc/group | awk -F: '{print $1}' | |
| $ cat /etc/group | cut -d: -f1 | |
| $ groups # list the groups for the current logged user | |
| $ groups barak #get a list of groups a specific user is in | |
| whoami | |
| grep "^$(whoami):" /etc/subuid | |
| grep "^$(whoami):" /etc/subgid | |
| id -u print only the effective user ID | |
| id -Gn | |
| id vagrant | |
| # The newgrp command allows a user to override the current primary group. | |
| # newgrp can be handy when you are working in a directory where all files must have the same group ownership | |
| newgrp microk8s #When you run the command, the system places you in a new shell and changes the name of your real group to the group specified with the Group parameter | |
| #If you’re listed as member of the group and the group has a password assigned, then you won’t be prompted | |
| #If there is no group password set, and the user is not listed as a member of the group, the user will be denied access | |
| #you are not a member of the developers group and not a root, then you’ll be prompted for a group password if your account doesn’t have a password assigned | |
| #If you’re root, then no prompted is presented. | |
| newgrp developers | |
| newgrp - developers #log in to the group developers | |
| sudo groupadd developers #create group developers | |
| sudo usermod -a -G developers richard | |
| sudo gpasswd developers | |
| #system account vs user account | |
| #System users will be created with no aging information in /etc/shadow | |
| #numeric identifiers are chosen in the SYS_UID_MIN–SYS_UID_MAX range defined in /etc/login.defs | |
| useradd --system appuser | |
| chage -l appuser | |
| useradd --system --shell=/usr/sbin/nologin <username> #create a system user (without home directory and login shell) | |
| useradd -r subversion #-r, --system create a system account | |
| adduser -r -s /bin/nologin subversion #create system account -s /sbin/nologin to disable any login shell | |
| adduser --system --no-create-home --group yourusername | |
| adduser subversion --system --group | |
| adduser -r -s /bin/nologin subversion | |
| $ sudo groupadd --system --gid 1002 appuser | |
| $ cat /etc/group | grep appuser | |
| appuser:x:1002: | |
| $ sudo useradd --no-log-init --system --uid 1001 --gid 1002 appuser | |
| $ cat /etc/passwd | grep appuser | |
| appuser:x:1001:1002::/home/appuser:/bin/sh | |
| # list a group's members | |
| $ sudo lid -g sales | |
| $ cut -d: -f1,4 /etc/passwd | grep $(getent group sales | cut -d: -f3) | cut -d: -f1 | |
| id username | |
| grep "docker" /etc/group | |
| grep -i --color 'root' /etc/group | |
| getent group -> List all groups | |
| cat /etc/group -> List all groups | |
| getent group vboxusers | |
| groups -> View the Groups a User Account | |
| groupmod -g 3000 foo -> assign a new GID to group called foo | |
| ------------------------------------------------------------------------------------------ | |
| #Files in /etc/skel are copied from this directory to new users’ home directories by certain account-creation tools | |
| #The files should be in all new users’ home directories should reside in /etc/skel. | |
| “skeleton” directory is defined in /etc/default/useradd file. | |
| # ls -lart /etc/skel | |
| # ls -ldi /etc/skel | |
| 33554552 drwxr-xr-x. 2 root root 62 Mar 24 2018 /etc/skel | |
| ------------------------------------------------------------------------------------------ | |
| valid login shells | |
| # cat /etc/shells #list all available shells | |
| # chsh -l | |
| chsh -s /bin/ksh #Regular user can change their shell to the ksh | |
| $ ps -p $$ | |
| PID TTY TIME CMD | |
| 56017 pts/0 00:00:00 bash | |
| grep tecmint /etc/passwd #view default login shell | |
| usermod --shell /bin/bash tecmint #change its login shell from /bin/sh to /bin/bash | |
| grep tecmint /etc/passwd #verify /bin/bash | |
| grep tecmint /etc/passwd #view default login shell | |
| chsh --shell /bin/bash tecmint #change its login shell from /bin/sh to /bin/bash | |
| grep tecmint /etc/passwd #verify /bin/bash | |
| $ sudo chsh -s /bin/ksh UserName #The superuser (root) changes the login shell for any account | |
| chsh -s /bin/ksh vagrant #set default login shell to /bin/ksh for vagrant user | |
| #open the /etc/passwd file, change manually | |
| vi /etc/passwd | |
| chsh vagrant -s /bin/rbash #change user vagrant's shell | |
| su - vagrant #login to activate shell | |
| whereis ksh | |
| grep --color ksh /etc/shells | |
| cat /etc/shells | |
| echo $SHELL | |
| ~ [23]$ ps -p $$ | |
| PID TTY TIME CMD | |
| 193052 pts/1 00:00:00 ksh | |
| ~ [27]$ ps -hp $$ | awk '{print $5}' | |
| -ksh | |
| ~ [28]$ echo $0 | |
| -ksh | |
| ~ [29]$ printf "%s\n" $0 | |
| -ksh | |
| ~ [30]$ readlink /proc/$$/exe | |
| /usr/bin/ksh93 | |
| awk -F: '/vagrant/ { print $7}' /etc/passwd #list user's shell type | |
| sudo ps -ef | egrep 'tty|pts' #Listing all shell types used by users | |
| $ w -h | awk '{print $2}' | xargs -L1 pgrep -oat | |
| verify user vagrant's bash | |
| # cat /etc/passwd | grep vagrant | |
| # echo $SHELL | |
| Reading Library editor | |
| $ cat /etc/inputrc | |
| keyboard bindings | |
| $ bind -v | |
| ------------------------------------------------------------------------------------------ | |
| semicolon ";" multiple commands on the same line | |
| backaslash "\" run commands longer than one line | |
| press tab key or twice ESC key, command completion | |
| "./" run a command from pwd | |
| ------------------------------------------------------------------------------------------ | |
| history file size setting | |
| $ cat /etc/profile | |
| $ echo $HISTSIZE | |
| $ echo $HISTFILE | |
| $ fc -l | |
| #Linux Command History with date and time, temporary | |
| HISTTIMEFORMAT="%d/%m/%y %H:%M " | |
| HISTTIMEFORMAT="%d/%m/%y %T " | |
| export HISTSIZE=0 #Disable the usage of history using HISTSIZE | |
| echo $HISTSIZE | |
| echo $HISTFILE | |
| export HISTCONTROL=ignoredups #Eliminate the continuous repeated entry from history using HISTCONTROL | |
| export HISTIGNORE="pwd:ls:ls -ltr:" #Ignore specific commands from the history using HISTIGNORE | |
| export HISTCONTROL=erasedups #Erase duplicates across the whole history using HISTCONTROL | |
| export HISTCONTROL=ignorespace #Force history not to remember a particular command using HISTCONTROL | |
| # service httpd stop [Note that there is a space at the beginning of service,to ignore this command from history] | |
| history -c #Clear all the previous history | |
| # !ps #Execute previous command that starts with a specific word | |
| # !4 #Execute a specific command from history | |
| # !-1 #execute the second last command | |
| # !! #run the last executed command, or press CTRL+P | |
| # !dconf #re-run the last command with the keyword ‘dconf’ in it | |
| #lastb #shows users that failed to login,review the /var/log/btmp file (containing failed login attempts) | |
| #the login history of users | |
| last logins | |
| last -R #review the contents of the /var/log/wtmp binary file | |
| last | grep sysadmin | |
| last -f /var/log/btmp #Use the last command to view the btmp file | |
| last mark #pass the user name | |
| last pts/0 #pass the tty | |
| last mark root pts/0 #specify multiple usernames and ttys | |
| last -p 2020-01-15 #find out who logged into the system on a specific date | |
| last -s 2020-02-13 -u 2020-02-18 #the -s (--since) and -t (--until) option to tell last to display the lines since or until the specified time | |
| last -F #y default, last doesn’t show the seconds and the year. Use the -F, --fulltimes option | |
| last -25 #last 25 logins | |
| last -i #IP address | |
| last -d #DNS address | |
| #the system last rebooted | |
| last reboot | |
| ------------------------------------------------------------------------------------------ | |
| echo $PATH | |
| view all the env variables | |
| $ export -p | |
| $ set | |
| Set an Environment Variable | |
| $ export MYAPP=1 | |
| holds the list of all directories that are searched by the shell when you type a command name | |
| $PATH | |
| system-wide | |
| $ cat /etc/profile | |
| single user | |
| $ cat .bash_profile | |
| # add PATH | |
| vi .bash_profile | |
| export PATH=$PATH:$HOME/Downloads/terraform | |
| system-wide prompt setting | |
| $ cat /etc/bashrc | |
| $ echo $PS1 | |
| ------------------------------------------------------------------------------------------ | |
| Display current libraries from the cache | |
| # ldconfig -p | head -5 | |
| Display libraries from every directory | |
| ldconfig -v | head | |
| # cat /etc/ld.so.conf | |
| ------------------------------------------------------------------------------------------ | |
| # number the lines in a file | |
| nl alphaservices | tee alphabetservices | |
| $ cat file1 | |
| 1. Asia: | |
| 2. Africa: | |
| 3. Europe: | |
| 4. North America: | |
| Display the contents of file.txt in octal format (one byte per integer) | |
| $ od -b file1 | |
| 0000000 061 056 040 101 163 151 141 072 012 062 056 040 101 146 162 151 | |
| 0000020 143 141 072 012 063 056 040 105 165 162 157 160 145 072 012 064 | |
| 0000040 056 040 116 157 162 164 150 040 101 155 145 162 151 143 141 072 | |
| 0000060 012 | |
| 0000061 | |
| Display the contents of file.txt in ASCII (character) format, with byte offsets displayed as hexadecimal. | |
| $ od -Ax -c file1 | |
| 000000 1 . A s i a : \n 2 . A f r i | |
| 000010 c a : \n 3 . E u r o p e : \n 4 | |
| 000020 . N o r t h A m e r i c a : | |
| 000030 \n | |
| 000031 | |
| ------------------------------------------------------------------------------------------ | |
| echo -n "hola" | od -A n -t x1 | sed 's/ *//g' | tr -d '\n' >> engineID_hex.txt #strips spaces remove newlines | |
| ------------------------------------------------------------------------------------------ | |
| # merge all files in the directory and split | |
| ls | xargs cat | tee file1 | split -5 | |
| # printing | |
| pr -h "title" file1 | |
| list mounted file systems | |
| $ cat /etc/mtab | |
| split -l 4 index.txt split_file #Split file based on number of lines | |
| split index.txt -l 4 --verbose | |
| split -l 4 -a 4 index.txt #Change in suffix length. By default, the suffix length is 2 | |
| split -l 4 -d index.txt #change the split files suffix to numeric | |
| split -l 4 index.txt split_index_ # create split output files with index suffix, | |
| split -l 4 -e index.txt #Avoid zero-sized split files | |
| split -n 3 index.txt #Create n chunks output files | |
| split -n 2 index.txt #Split the file into two files of equal length | |
| #split the file index.txt into separate files called indexaa, indexab, …..with each file containing 16 bytes of data | |
| split -b 16 index.txt index | |
| split -b=1M -d file.txt file --additional-suffix=.txt | |
| split -b 10M -d system.log system_split.log | |
| ~$ cat test.txt | wc -l | |
| 40 | |
| ~$ split --numeric-suffixes=2 --additional-suffix=.txt -l 22 test.txt file | |
| $ ls -lai file* | |
| 2139 -rw-rw-r-- 1 vagrant vagrant 660 Mar 21 11:01 file02.txt | |
| 5482 -rw-rw-r-- 1 vagrant vagrant 660 Mar 21 11:01 file03.txt | |
| 5483 -rw-rw-r-- 1 vagrant vagrant 660 Mar 21 11:01 file04.txt | |
| 18296 -rw-rw-r-- 1 vagrant vagrant 220 Mar 21 11:01 file05.txt | |
| $ cat file04.txt | wc -l | |
| 12 | |
| $ cat file05.txt | wc -l | |
| 4 | |
| ----------------------------------------------------------------------------------------------------- | |
| u stands for user. | |
| g stands for group. | |
| o stands for others. | |
| a stands for all. | |
| same output: | |
| chmod -R 755 /var/www/html #change the permissions of all files and subdirectories under the /var/www/html directory to 755 | |
| chmod +x somefile (Based on umask value) | |
| chmod a+x somefile, chmod ugo+x somefile (Without considering umask value), add the execute permission for everyone | |
| chmod 644 a.txt | |
| stat -c %a a.txt # verify permission granted is 644 | |
| ------------------------------------------------------------------------------------------ | |
| Applying SUID Permission Numerically | |
| # chmod 4755 /bin/ping | |
| Removing SUID by Numerically | |
| chmod 0755 /bin/ping | |
| Applying SUID Permission to ping binary file Alphabetically | |
| # chmod u+s /bin/ping | |
| Removing SUID Permission | |
| chmod u-s /bin/ping | |
| ------------------------------------------------------------------------------------------ | |
| # Applying SGID Permission | |
| chmod g+s /database/ | |
| chmod 2775 database/ | |
| # Remove SGID Alphabetically | |
| chmod g-s /database/ | |
| chmod 0775 /database | |
| ------------------------------------------------------------------------------------------ | |
| a sticky bit is now in place and only root, file or directory owners can rename and delete files | |
| # chmod +t /var/share/ | |
| # ls -ld /var/share/ | |
| drwxrwxrwt. 2 root root 4096 Mar 5 11:21 /var/share/ | |
| chmod 0777 somefile (octal) | |
| chmod 777 somefile (decimal) | |
| chmod 0710 mydir ; ls -ld mydir | |
| chmod 00710 mydir ; ls -ld mydir | |
| ------------------------------------------------------------------------------------------ | |
| # quota settings | |
| sudo apt update ; sudo apt install quota -y | |
| quota --version | |
| find /lib/modules/`uname -r` -type f -name '*quota_v*.ko*' | |
| sudo mount -o remount / | |
| cat /proc/mounts | grep ' / | |
| sudo quotacheck -ugm / | |
| sudo quotaon -v / | |
| sudo setquota -u member1 200M 240M 0 0 / | |
| sudo quota -vs member1 | |
| sudo setquota -t 864000 864000 / | |
| sudo repquota -s / | |
| ------------------------------------------------------------------------------------------ | |
| # ldd (Unix) ldd (List Dynamic Dependencies) | |
| ldd /bin/ls | |
| # display unused direct dependencies | |
| ldd -u /bin/ping | |
| # more information | |
| ldd -v /bin/ping | |
| ------------------------------------------------------------------------------------------ | |
| # rename root | |
| $ head -2 /etc/passwd | |
| root:x:0:0:root:/root:/bin/nologin | |
| rootmon:x:0:0:root:/root:/bin/bash | |
| $ sudo passwd rootmon | |
| $ su - rootmon | |
| # pwd | |
| /root | |
| #gain a root shell is by adding a new user to /etc/passwd who has the UID 0 | |
| #any user with UID 0 is effectively root | |
| #root2 is the username | |
| #WVLY0mgH0RtUI is the encrypted password we want him to have. Unencrypted, the password is mrcake, in this case | |
| #0:0 means the user id and group id are both 0 | |
| #root is a comment field | |
| #/root is the home directory | |
| #/bin/bash is the default shell | |
| root2:WVLY0mgH0RtUI:0:0:root:/root:/bin/bash | |
| #Administrative databases in Unix,getent – get entries from administrative database | |
| passwd – can be used to confirm usernames, userids, home directories and full names of your users | |
| group – all the information about Unix groups known to your system | |
| services – all the Unix services configured on your system | |
| networks – networking information – what networks your system belongs to | |
| protocols – everything your system knows about network protocols | |
| $ getent hosts # /etc/hosts file | |
| $ getent hosts vg-ubuntu-01 double-check which IPs this hostname points to | |
| $ getent networks #check the network and IP address of your system | |
| $ getent services 20 #Use “services” with the port number to find the service name and its protocol | |
| #List Users(system and normal users) on Linux using the /etc/passwd File, normal user has a real login shell and a home directory. | |
| awk -F: '{ print $1}' /etc/passwd | |
| cat /etc/passwd | awk -F: '{print $1}' | |
| awk -F: '{ print $1}' /etc/passwd | wc -l # get the # of users | |
| cut -d: -f1 /etc/passwd | |
| cat /etc/passwd | cut -d: -f1 | |
| getent passwd # list users | |
| getent passwd | awk -F ":" '{print $1}' | |
| getent passwd | cut -d: -f1 | |
| getent passwd # equivalent to cat /etc/passwd | |
| getent passwd rahul #details for a particular user | |
| getent passwd 0 #find a username by UID | |
| $ cut -d":" -f1 /etc/passwd #list all users | |
| #list normal user names | |
| awk -F: '{if($3 >= 1000 && $3 < 2**16-2) print $1}' /etc/passwd | |
| awk -F: '{if(($3 >= 500)&&($3 <65534)) print $1}' /etc/passwd | |
| awk -F: '{if(!(( $2 == "!!")||($2 == "*"))) print $1}' /etc/shadow | |
| grep -E ":[0-9]{4,6}:[0-9]{4,6}:" /etc/passwd | cut -d: -f1 | |
| $ getent passwd | awk 'NR==FNR { if ($1 ~ /^UID_(MIN|MAX)$/) m[$1] = $2; next } | |
| { split ($0, a, /:/); | |
| if (a[3] >= m["UID_MIN"] && a[3] <= m["UID_MAX"] && a[7] !~ /(false|nologin)$/) | |
| print a[1] }' /etc/login.defs - | |
| $ getent passwd | \ | |
| nologin|false)> grep -vE '(nologin|false)$' | \ | |
| : -v mi> awk -F: -v min=`awk '/^UID_MIN/ {print $2}' /etc/login.defs` \ | |
| X/ {p> -v max=`awk '/^UID_MAX/ {print $2}' /etc/login.defs` \ | |
| $3 >= > '{if(($3 >= min)&&($3 <= max)) print $1}' | \ | |
| t -u> sort -u | |
| grep -E '^UID_MIN|^UID_MAX' /etc/login.defs #Each user has a numeric user ID called UID. If not specified automatically selected from the /etc/login.defs | |
| getent passwd {1000..60000} #list all normal users depending on UID_MIN/UID_MAX in /etc/login.defs | |
| eval getent passwd {$(awk '/^UID_MIN/ {print $2}' /etc/login.defs)..$(awk '/^UID_MAX/ {print $2}' /etc/login.defs)} | cut -d: -f1 | |
| # generic,UID_MIN and UID_MIN values may be different, | |
| eval getent passwd {$(awk '/^UID_MIN/ {print $2}' /etc/login.defs)..$(awk '/^UID_MAX/ {print $2}' /etc/login.defs)} | |
| awk -F ":" '{print $5}' /etc/passwd #print the fifth field | |
| getent passwd $UID| awk -F ":" '{print $5}' | |
| GECOS fields (which stands for "General Electric Comprehensive Operating System") | |
| username:password:userid:groupid:gecos:home-dir:shell | |
| GECOS are divided as: | |
| :FullName,RoomAddress,WorkPhone,HomePhone,Others: | |
| sally:x:0:529:Sally Jones:/home/myhome:/bin/passwd #might be used on, a Samba fle server or a POP mail server to enable users to change their passwords via SSH without granting login shell access. | |
| ------------------------------------------------------------------------------------------ | |
| # enable the root account | |
| sudo passwd root | |
| ------------------------------------------------------------------------------------------ | |
| # send an email from command line | |
| mail -s “Hello world” [email protected] | |
| echo “This will go into the body of the mail.” | mail -s “Hello world” [email protected] | |
| df -h | mail -s “disk space report” [email protected] | |
| ------------------------------------------------------------------------------------------ | |
| # check a file system for errors? | |
| fsck | |
| fsck.ext3 | |
| fsck.nfs | |
| fsck.ext2 | |
| fsck.vfat | |
| fsck.reiserfs | |
| fsck.msdos | |
| In order to run fsck on the root partition, the root partition must be mounted as readonly | |
| ------------------------------------------------------------------------------------------ | |
| # list of drives that are mounted at boot | |
| /etc/fstab | |
| # runs as a daemon and typically has PID 1 | |
| # change the default runlevel upon boot up. | |
| /etc/inittab | |
| chkconfig --list #list of all runlevels and services used by them | |
| chkconfig vnicen.sh off #Ensure that the vnicen does not start upon reboot | |
| chkconfig --list | grep vnicen | |
| chkconfig --level 2345 sshd on #enable sshd startup | |
| syslogd # daemon is responsible for tracking events on the system | |
| # set which window man-ager you want to use when logging in to X from that account | |
| # edit in your home directory to change which window manager you want to use | |
| ~/.xinitrc | |
| ------------------------------------------------------------------------------------------ | |
| find the number of processing units (CPU) available on a system | |
| nproc | |
| nproc --all | |
| echo "Threads/core: $(nproc --all)" | |
| lscpu #the number of physical CPU cores | |
| lscpu | egrep 'Model name|Socket|Thread|NUMA|CPU\(s\)' | |
| lscpu -p | |
| grep 'model name' /proc/cpuinfo | wc -l | |
| grep 'cpu cores' /proc/cpuinfo | uniq | |
| echo "CPU threads: $(grep -c processor /proc/cpuinfo)" | |
| cat /proc/cpuinfo | |
| grep -c ^processor /proc/cpuinfo | |
| cat /proc/cpuinfo | grep 'core id' #get the actual number of cores | |
| getconf _NPROCESSORS_ONLN && echo "Number of CPU/cores online at $HOSTNAME: $(getconf _NPROCESSORS_ONLN)" | |
| ------------------------------------------------------------------------------------------ | |
| $ seq -s";" -w 1 12 | |
| 01;02;03;04;05;06;07;08;09;10;11;12 | |
| # write dummy lines into a file | |
| $ seq -s ' ' 23 > file && cat file | |
| # read dummy lines from a file | |
| $ awk '(NR % 6 == 1) {print; for(i=1; i<6 && getline ; i++) { print }; printf "\n"}' RS=' ' ORS=' ' file | |
| 1 2 3 4 5 6 | |
| 7 8 9 10 11 12 | |
| 13 14 15 16 17 18 | |
| 19 20 21 22 23 | |
| # Create a dummy file | |
| echo -e "1\n2\n3\n4" > testfile.txt | |
| $ echo "3997e1" > ids.txt #write | |
| $ echo "45697676107" >> ids.txt #append | |
| ------------------------------------------------------------------------------------------ | |
| protection from inadvertently overwriting files when copying | |
| ~/.bashrc | |
| alias cp='cp -i' | |
| ------------------------------------------------------------------------------------------ | |
| $ sudo tree -d /var/log/ --du -sch | |
| /var/log/ | |
| ├── [4.0K] dist-upgrade | |
| ├── [4.0K] fsck | |
| ├── [4.0K] lxd | |
| ├── [4.0K] apt | |
| └── [4.0K] unattended-upgrades | |
| $ sudo tree /var/log/ --du -h | |
| $ sudo tree -a /var/log #display hidden files | |
| $ tree -daC | |
| $ tree -f #view the full path for each directory and file | |
| $ sudo tree -f -L 3 | |
| $ sudo tree -f -P cata* #only list files that match cata*, so files such as Catalina.sh, catalina.bat, etc | |
| $ tree -P "*.log" | |
| $ sudo tree -f -I *log /var/log #-I option,display all the files that do not match the specified pattern | |
| $ sudo tree -d -I *log /var/log | |
| $ tree -I "*.log" | |
| $ sudo tree -f --prune #prune empty directories from the output | |
| $ sudo tree -f -p #-p which prints the file type and permissions for each file | |
| $ sudo tree -f -pug #print the username,the group name | |
| $ sudo tree -f -pugs #print the size of each file in bytes along with the name using the -s option | |
| $ sudo tree -f -pugh #human-readable format, use the -h flag | |
| $ sudo tree -f -pug -h -D #display the date of the last modification time for each sub-directory or file | |
| $ tree -d -L 3 # the depth of directory tree in output | |
| tree -vr #sort the files from Z-A | |
| $ tree -L 2 | |
| tree -J #the output is in JSON format | |
| $ sudo tree -o direc_tree.txt | |
| ------------------------------------------------------------------------------------------ | |
| ipcs (InterProcess Communication System) provides a report on the semaphore, shared memory & message queue | |
| ipcs -u | |
| ipcs -m | |
| ------------------------------------------------------------------------------------------ | |
| nslookup github.com | |
| nslookup 140.82.118.4 | |
| nslookup -query=mx github.com | |
| nslookup -query=ns github.com | |
| nslookup -query=any github.com | |
| nslookup -query=soa github.com | |
| nslookup -query=soa port=54 github.com | |
| nslookup -debug github.com | |
| ------------------------------------------------------------------------------------------ | |
| The command shell interprets the && as the logical AND.the second command will be executed only when the first one has been succcefully executed | |
| A double ampersand && in Bash means AND and can be used to separate a list of commands to be run sequentially. | |
| Commands separated by a double ampersand && are to be run synchronously, with each one running only if the last did not fail (a fail is interpreted as returning a non-zero return status). | |
| && AND – execute both, return true of both succeed | |
| ; sequential execution, return status is that of the last in the list | |
| $ mkdir /workspace ; mkdir /entrypoint | |
| mkdir: cannot create directory ‘/workspace’: Permission denied | |
| mkdir: cannot create directory ‘/entrypoint’: Permission denied | |
| $ mkdir /workspace && mkdir /entrypoint | |
| mkdir: cannot create directory ‘/workspace’: Permission denied | |
| ------------------------------------------------------------------------------------------ | |
| mkdir -p first/second/third #If the first and second directories do not exist, mkdir creates these directories | |
| mkdir -m a=rwx first/second/third #set the file modes, i.e. permissions, etc | |
| ------------------------------------------------------------------------------------------ | |
| disable and stop service | |
| $ sudo systemctl disable --now zabbix-server.service | |
| enable and start service | |
| $ sudo systemctl enable --now zabbix-server.service # enable and start the service | |
| chkconfig tgtd on #configure it to start Automatically while system start-up | |
| chkconfig --list tgtd #verify that the run level configured correctly for the tgtd service | |
| chkconfig --list #shows SysV services only and does not include native systemd services. | |
| chkconfig | grep snmpd | |
| systemctl list-units --all | |
| systemctl list-unit-files | |
| systemctl list-units --all --state=inactive | |
| systemctl list-units --type=service #only active service units | |
| systemctl cat sshd.service #Displaying a Unit File | |
| sudo systemctl edit nginx.service | |
| sudo systemctl edit --full nginx.service | |
| sudo systemctl daemon-reload | |
| systemctl list-unit-files --type=target | |
| systemctl list-units --type=target | |
| systemctl list-dependencies sshd.service #Displaying Dependencies | |
| systemctl show sshd.service #Checking Unit Properties | |
| systemctl show sshd.service -p Conflicts #display a single property,pass the -p flag with the property name | |
| sudo systemctl mask nginx.service #the ability to mark a unit as completely unstartable, automatically or manually, by linking it to /dev/null. This is called masking the unit | |
| ------------------------------------------------------------------------------------------ | |
| ls -laZ ~/.ssh | |
| # change the security context to system_u:object_r:usr_t:s0 | |
| chcon -R -v system_u:object_r:usr_t:s0 ~/.ssh/ | |
| ------------------------------------------------------------------------------------------ | |
| problem: | |
| never edit directly '/etc/sudoers' file | |
| $ sudo visudo | |
| >>> /etc/sudoers: syntax error near line 28 <<< | |
| sudo: parse error in /etc/sudoers near line 28 | |
| sudo: no valid sudoers sources found, quitting | |
| fix: | |
| pkexec visudo | |
| #includedir /etc/sudoers -> #includedir /etc/sudoers.d #change last line | |
| sudo mount /dev/sda1 /mnt #mount the installed Ubuntu system's root filesystem | |
| sudo visudo -f /mnt/etc/sudoers #edit the installed system's sudoers file | |
| pkexec visudo -f /etc/sudoers.d/filename #edit configuration files | |
| ------------------------------------------------------------------------------------------ | |
| problem: sleep: invalid time interval `2\r' | |
| fix: sudo cat test.sh | sudo tr -d '\r' | sudo tee test2.sh | |
| ------------------------------------------------------------------------------------------ | |
| $ diff 1.txt 2.txt # display the differences in the files by comparing the files line by line | |
| $ diff -c 1.txt 2.txt | |
| $ diff 1.txt 2.txt -u | |
| $ diff 1.txt 2.txt -i | |
| $ diff 1.txt 2.txt --color | |
| $ diff 1.txt 2.txt -s | |
| $diff -i test_file_1.txt test_file_2.txt #ignoring the case sensitivity | |
| $diff -y -W 60 test_file_1.txt test_file_2.txt #view the difference,The “-W” indicates the width between the content of two files | |
| $diff -q test_file_1.txt test_file_2.txt #“-q” option with the “diff” command gives you output in one line | |
| $diff -u test_file_1.txt test_file_2.txt # | |
| #write the difference between two files into a file | |
| diff a.txt b.txt|grep ">"|cut -c 3- > foo.txt | |
| #-q, --brief report only when files differ | |
| #-s, --report-identical-files report when two files are the same | |
| diff -sq /tmp/file1 /tmp/file2 | |
| diff chap1.back chap1 #compare two files | |
| #If two lines differ only in the number of spaces and tabs between words, the diff -w command considers them to be the same. | |
| #compare two files compare two files while ignoring differences in the amount of white space | |
| diff -w prog.c.bak prog.c | |
| #create a file containing commands that the ed command can use to reconstruct one file from another | |
| #creates a file named new.to.old.ed that contains the ed subcommands to change chap2 | |
| #back into the version of the text found in chap2.old | |
| diff -e chap2 chap2.old >new.to.old.ed | |
| # in parentheses add 1,$p to the end of the editing commands sent to the ed editor. | |
| #The 1,$p causes the ed command to write the file to standard output after editing it | |
| #then piped to the ed command (| ed), and the editor reads it as standard input | |
| #The - flag causes the ed command not to display the file size and other extra information | |
| #because it would be mixed with the text of chap2.old. | |
| (cat new.to.old.ed ; echo '1,$p') | ed - chap2 >chap2.old | |
| #compare two text files containing UTF-8 characters and show the differences | |
| diff -W filecodeset=UTF-8,pgmcodeset=IBM-1047 myUtf8File01 myUtf8File02 | |
| #compare two text files containing EBCDIC characters and show the differences | |
| diff -B myMisTaggedFile01 myMisTaggedFile02 | |
| ------------------------------------------------------------------------------------------ | |
| Local to Remote: rsync [OPTION]... -e ssh [SRC]... [USER@]HOST:DEST | |
| Remote to Local: rsync [OPTION]... -e ssh [USER@]HOST:SRC... [DEST] | |
| #When the trailing slash "/" is omitted the source directory will be copied inside the destination directory | |
| #transfer the local directory to the directory on a remote machine | |
| $ rsync -avz -e "ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null" --progress /home/filerunner/dir1 vg-ubuntu-02:/tmp | |
| $ ls /tmp/dir1 | |
| a.txt | |
| #When the source directory has a trailing slash "/", rsync will copy only the contents of the source directory to the destination directory | |
| $ rsync -avz -e "ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null" --progress /home/filerunner/dir1/ vg-ubuntu-02:/tmp | |
| $ ls /tmp | |
| a.txt | |
| #dry run mode, | |
| rsync -azhv -e "ssh -p 2212" --dry-run /home/bob/test_219 | |
| rsync -a -e "ssh -p 3322" /home/linuxize/images/ [email protected]:/var/www/images/ #if SSH is listening on port 3322 | |
| #transfer a single file /opt/file.zip from the local system to the /var/www/ directory on the remote system with IP 12.12.12.12 | |
| #If the file exists on the remote server it is overwritten | |
| rsync -a /opt/file.zip [email protected]:/var/www/ | |
| #save the file under a different name | |
| rsync -a /opt/file.zip [email protected]:/var/www/file2.zip | |
| #transfer data from a remote to a local machine | |
| rsync -a [email protected]:/var/www/file.zip /opt/ | |
| #synchronize the local and remote directory | |
| rsync -a /home/linuxize/images/ [email protected]:/var/www/images/ | |
| #use the --delete option if you want to synchronize the local and remote directory | |
| #delete files in the destination directory if they don’t exist in the source directory. | |
| rsync -a --delete /home/linuxize/images/ [email protected]:/var/www/images/ | |
| #the “-r” option for “recursive” and the “-a” option for “all” (otherwise non-regular files will be skipped) | |
| #copy the “/etc” folder to the “/etc_backup” of the remote server | |
| #with the “devconnected” username to server 192.168.178.35/24 | |
| rsync -ar /etc [email protected]:/etc_backup | |
| #Similarly,copy the content of the “/etc/ directory rather than the directory itself | |
| rsync -ar /etc/* [email protected]:/etc_backup/ | |
| # taggged with the current date | |
| rsync -ar /etc/* [email protected]:/etc_backup/etc_$(date "+%F") | |
| #from local to remote server with private key | |
| rsync -auvz -e "ssh -i private-key-file" source destination #Using rsync With SSH and Private Key | |
| rsync -auvz -e "ssh -i /home/yourUserName/.ssh/yourUserName-rsync-key" junk.txt [email protected] | |
| rsync -avzhe ssh backup.tar.gz [email protected]:/backups/ | |
| rsync -avzhe ssh --progress /root/rpmpkgs [email protected]:/root/rpmpkgs | |
| #from remote to local server | |
| rsync -avzh [email protected]:/root/rpmpkgs /tmp/myrpms | |
| rsync -avze ssh --include 'R*' --exclude '*' [email protected]:/var/lib/rpm/ /root/rpm | |
| ------------------------------------------------------------------------------------------ | |
| #copy the “/etc” directory to a backup server located at 192.168.178.35 in the “/etc_backup” folder | |
| scp -r /etc [email protected]:/etc_backup/ | |
| # taggged with the current date | |
| scp -r /etc [email protected]:/etc_backup/etc_$(date "+%F") | |
| scp [email protected]:foobar.txt /some/local/directory-> Copy the file "foobar.txt" from a remote host to the local host | |
| scp file.txt [email protected]:/remote/directory/newfilename.txt # save the file under a different name,Omitting the filename from the destination location copies the file with the original name. | |
| scp foobar.txt [email protected]:/some/remote/directory -> Copy the file "foobar.txt" from the local host to a remote host | |
| scp [email protected]:/some/remote/directory/foobar.txt [email protected]:/some/remote/directory/ ->Copy the file "foobar.txt" from remote host "rh1.edu" to remote host "rh2.edu" | |
| scp -P 2322 file.txt [email protected]:/remote/directory #the remote host is listening on a port other than the default 22 | |
| scp -r /local/directory [email protected]:/remote/directory #copy a directory from a local to remote system,use the -r flag for recursive | |
| # don’t have to log in to one of the servers to transfer files from one to another remote machine. | |
| #copy the file /files/file.txt from the remote host host1.com to the directory /files on the remote host host2.com | |
| scp [email protected]:/files/file.txt [email protected]:/files | |
| scp -3 [email protected]:/files/file.txt [email protected]:/files #route the traffic through the local host (machine on which the command is issued), use the -3 option | |
| ------------------------------------------------------------------------------------------ | |
| #cp interpret main as a directory to place scala,doesn't exist, cp will throw an error. | |
| cp -av /home/jake/transit/scalaProjects/scalaML/src/main/scala -t /home/jake/project/__workspace/scalaProjects/scalaML/src/main/ | |
| #Copy Directory Content Recursively | |
| cp -R bashdir bashdir-bck | |
| cp -R /etc/* /etc_backup | |
| cp -R /etc/* /home/* /backup_folder # copy the “/etc” directory and “/home” directory. | |
| #copies the folder Misc and all its contents (the -r, or "recursive," option indicates the contents as well as the folder or file itself) into the folder /media/clh/4388-D5FE | |
| cp -r Misc /media/clh/4388-D5FE # | |
| #copy over only the new files,use the "update" and "verbose" options | |
| cp -ruv Misc /media/clh/4388-D5FE | |
| # a file called test1.py, which is the original, and another called test1.py.~1~, which is the backup file. | |
| cp --force --backup=numbered test1.py test1.py | |
| cp /home/usr/dir/{file1,file2,file3,file4} /home/usr/destination/ #copy multiple files | |
| cp -rp /copying/from/{folder1/,folder2/,folder3/} path/to/folder #p is for copying the folder permission | |
| cp /home/usr/dir/file{1..4} /tmp #if the all the files have the same prefix but different endings | |
| ------------------------------------------------------------------------------------------ | |
| #brace expansions | |
| $ sudo cp ~/a.txt{,.orig} #backup of file in the current directory, copy shortcut | |
| $ ls | |
| a.txt a.txt.orig | |
| $ echo g{et,ot,it}em | |
| getem gotem gitem | |
| $ echo {00..8..2} #loop with increase 2 | |
| 00 02 04 06 08 | |
| $ echo {D..T..4} #loop with increase 4 | |
| D H L P T | |
| $ mv error.log{,.OLD} #expands to "mv error.log error.log.OLD") | |
| ------------------------------------------------------------------------------------------ | |
| cmp file1.txt file2.txt #cmp command reports the byte and line number if a difference is found | |
| cmp --silent file1 file2 && echo 'SUCCESS: Files Are Identical' || echo 'Files Are Different' | |
| cmp --silent $old $new || echo "files are different" | |
| #if= defines the source drive and of= defines the file or location where data saved | |
| # dd if=/dev/sda of=/dev/sdb | |
| # dd if=/dev/sda of=/home/username/sdadisk.img #create an .img archive of the /dev/sda drive and save it to the home directory | |
| # dd if=/dev/sda2 of=/home/username/partition2.img bs=4096 | |
| #if= takes the image to restore, and of= takes the target write the image | |
| # dd if=sdadisk.img of=/dev/sdb | |
| create a compressed image of a remote drive using SSH and save the resulting archive to local machine | |
| # ssh [email protected] "dd if=/dev/sda | gzip -1 -" | dd of=backup.gz | |
| dd if=text.ascii of=text.ebcdic conv=ebcdic #convert an ASCII text file to EBCDIC | |
| #convert the variable-length record ASCII file /etc/passwd to a file of 132-byte fixed-length EBCDIC records | |
| dd if=/etc/passwd cbs=132 conv=ebcdic of=/tmp/passwd.ebcdic | |
| #convert the 132-byte-per-record EBCDIC file to variable-length ASCII lines in lowercase | |
| dd if=/tmp/passwd.ebcdic cbs=132 conv=ascii of=/tmp/passwd.ascii | |
| #copy blocks from a tape with 1KB blocks to another tape using 2KB blocks | |
| dd if=/dev/rmt0 ibs=1024 obs=2048 of=/dev/rmt1 | |
| ls -l | dd conv=ucase #displays a long listing of the current directory in uppercase. | |
| dd if=/dev/zero of=/dev/sda1 #Wiping disks with dd,writing zeros | |
| # dd if=/dev/urandom of=/dev/sda1 #Wiping disks with dd,writing random characters | |
| # dd if=/dev/urandom | pv | dd of=/dev/sda1 #Monitoring dd operations,Pipe Viewer (sudo apt install pv on Ubuntu) | |
| #create a large file of random conten | |
| $ dd if=/dev/urandom of=/tmp/file1 count=1K bs=1MB | |
| #copy file1 to file2, and append different characters to each file | |
| $ cp /tmp/file1 /tmp/file2 | |
| $ echo 1 >> /tmp/file1 | |
| $ echo 2 >> /tmp/file2 | |
| #use the time command to measure the time taken | |
| $ time cmp -s /tmp/file1 /tmp/file2 | |
| $ time diff -sq /tmp/file1 /tmp/file2 | |
| $ time sha1sum /tmp/file1 | |
| $ time sha1sum /tmp/file2 | |
| #Empty File Content by Redirecting to Null | |
| # > access.log | |
| # : > access.log #: is a shell built-in command | |
| # true > access.log | |
| # cat /dev/null > access.log | |
| # cp /dev/null access.log | |
| # dd if=/dev/null of=access.log | |
| # echo "" > access.log | |
| # echo > access.log | |
| # echo -n "" > access.log #use the flag -n which tells echo to not output the trailing newline | |
| # truncate -s 0 access.log | |
| dd if=/dev/urandom of=test.file bs=1M count=100 ; time diff -q test.file test.copy && echo diff true || echo diff false ; \ | |
| time cmp -s test.file test.copy && echo cmp true || echo | |
| vagrant@lampstack-01:~$ echo "file" > file1.txt | |
| vagrant@lampstack-01:~$ cp file1.txt file2.txt | |
| vagrant@lampstack-01:~$ cmp file1.txt file2.txt #cmp command reports the byte and line number if a difference is found | |
| vagrant@lampstack-01:~$ sudo cmp file1.txt file2.txt | |
| vagrant@lampstack-01:~$ echo "identical file1" >> file1.txt | |
| vagrant@lampstack-01:~$ cat file1.txt | |
| file | |
| identical file1 | |
| vagrant@lampstack-01:~$ cat file2.txt | |
| file | |
| vagrant@lampstack-01:~$ cmp file1.txt file2.txt #cmp command reports the byte and line number if a difference is found | |
| cmp: EOF on file2.txt after byte 5, line 1 | |
| vagrant@lampstack-01:~$ diff file1.txt file2.txt | |
| 2d1 | |
| < identical file1 | |
| ------------------------- ----------------------------------------------------------------- | |
| # approval trick | |
| $ yes | sudo yum install puppet | |
| # user has to type 'y' for each query | |
| $ yes | rm -ri test | |
| ------------------------- ----------------------------------------------------------------- | |
| #oracle java download | |
| wget --no-cookies \ | |
| --no-check-certificate \ | |
| --header "Cookie: oraclelicense=accept-securebackup-cookie" \ | |
| "https://download.oracle.com/otn-pub/java/jdk/13.0.1+9/cec27d702aa74d5a8630c65ae61e4305/jdk-13.0.1_linux-x64_bin.tar.gz" \ | |
| -O jdk-7-linux-x64.tar.gz | |
| curl --silent example.com | sha256sum | |
| curl --silent --output - example.com | sha256sum #the o flag is redundant since the output is piped to bash (for execution) - not to a file | |
| #-L in case the page has moved curl will redirect the request to the new address | |
| #-o output to a file instead of stdout (usually the screen) | |
| curl -LO http://example.com/ | |
| curl -LO -H "Cookie: oraclelicense=accept-securebackup-cookie" \ | |
| https://download.oracle.com/otn-pub/java/jdk/13.0.1+9/cec27d702aa74d5a8630c65ae61e4305/jdk-13.0.1_linux-x64_bin.tar.gz | |
| ------------------------------------------------------------------------------------------ | |
| ------------------------------------------------------------------------------------------ | |
| hostnamectl set-hostname vg-checkmk-client | |
| echo "172.28.128.15 vg-checkmk-client.local vg-checkmk-client" |sudo tee -a /etc/hosts | |
| echo "nameserver 8.8.8.8" |sudo tee -a /etc/resolv.conf | |
| problem: | |
| #append text to a file when using sudo | |
| sudo echo "172.28.128.15 vg-checkmk-client.local vg-checkmk-client" >> /etc/hosts | |
| -bash: /etc/hosts: Permission denied | |
| fix: | |
| #running bash/sh shell with root privileges and redirection took place in that shell session | |
| $ sudo sh -c 'echo "172.28.128.15 vg-checkmk-client.local vg-checkmk-client" >> /etc/hosts' | |
| $ sudo sh -c 'echo "JAVA_HOME=/usr/lib/jvm/java-6-sun" >> /etc/profile' | |
| $ sudo bash -c 'echo "JAVA_HOME=/usr/lib/jvm/java-6-sun" >> /etc/profile' | |
| $ sudo tee -a /etc/profile.d/java.sh << 'EOF' | |
| # configures JAVA | |
| JAVA_HOME=/usr/lib/jvm/java-8-oracle | |
| export JAVA_HOME | |
| export PATH=$PATH:$JAVA_HOME/bin | |
| EOF | |
| $ sudo sed -i '$a something' /etc/config_file | |
| ------------------------------------------------------------------------------------------ | |
| #File Creation Times | |
| vagrant@lampstack-01:/tmp/nexus$ df -h | |
| Filesystem Size Used Avail Use% Mounted on | |
| udev 205M 0 205M 0% /dev | |
| tmpfs 48M 7.8M 41M 17% /run | |
| /dev/mapper/vagrant--vg-root 62G 4.3G 55G 8% / | |
| tmpfs 240M 0 240M 0% /dev/shm | |
| tmpfs 5.0M 0 5.0M 0% /run/lock | |
| tmpfs 240M 0 240M 0% /sys/fs/cgroup | |
| vagrant 420G 375G 46G 90% /vagrant | |
| tmpfs 48M 0 48M 0% /run/user/1000 | |
| vagrant@lampstack-01:/tmp/nexus$ ls -i Dockerfile | |
| 3808483 Dockerfile | |
| vagrant@lampstack-01:/tmp/nexus$ sudo debugfs -R 'stat <3808483>' /dev/mapper/vagrant--vg-root | |
| debugfs 1.44.6 (5-Mar-2019) | |
| vagrant@lampstack-01:/tmp/nexus$ vagrant@lampstack-01:/tmp/nexus$ sudo debugfs -R 'stat <3808483>' /dev/mapper/vagrant--vg-root | grep crtime | |
| debugfs 1.44.6 (5-Mar-2019) | |
| crtime: 0x5e4f0f92:b6a11330 -- Thu Feb 20 23:00:34 2020 | |
| ------------------------------------------------------------------------------------------ | |
| #how to view gz gunzip files | |
| zcat test2.txt.gz #see the content of the compressed file | |
| zcat test.txt.gz test2.txt.gz #see the content of the compressed files,multiple inputs | |
| zcat test2.txt #uncompress files that have the correct magic number whether they have a .gz suffix or not | |
| zcat test2.txt.gz | more | |
| zcat test2.txt.gz | less | |
| zmore test2.txt.gz | |
| zless test2.txt.gz | |
| zless -f test2.txt #display file contents in output whether or not the file is compressed | |
| # search string in multiple .gz file | |
| zgrep -i -H "pattern match" /somedir/filename*.gz | |
| zgrep -i -H "pattern match" /somedir/filename*.gz | grep "pattern 2nd" | |
| find /somedir/ -name "log.202011917*.gz" -exec zgrep "somestring" \{\} \; | |
| find /somedir/ -name 'log.202011917' -print0 | xargs -0 zgrep "somestring" #prints file path inc. folder | |
| ------------------------------------------------------------------------------------------ | |
| #Hosts File | |
| Windows 10 - "C:\Windows\System32\drivers\etc\hosts" | |
| Linux - "/etc/hosts" | |
| Mac OS X - "/private/etc/hosts" | |
| ------------------------------------------------------------------------------------------ | |
| type -a ll #if command is an alias or not | |
| type -p dash | |
| ------------------------------------------------------------------------------------------ | |
| ------------------------------------------------------------------------------------------ | |
| echo $? #get the exit status of the previously executed command, http://www.tldp.org/LDP/abs/html/exitcodes.html | |
| echo $? # Expands to the exit status (exit code) of the most recently executed foreground pipeline,return the exit status of last command | |
| exits with a status code 0 #success | |
| exits with a status code 1 #failure | |
| command && echo "success: $?" || echo "fail: $?" #test if the command failed | |
| if [ $? -eq 0 ]; then echo "success: $?"; fi | |
| $ echo "hola el mundo" > file.txt | |
| $ cat file.txt && echo "success: $?" || echo "fail: $?" | |
| hola el mundo | |
| success: 0 | |
| $ cat filedoesnotexist.txt && echo "success: $?" || echo "fail: $?" | |
| cat: filedoesnotexist.txt: No such file or directory | |
| fail: 1 | |
| cat 'doesnotexist.txt' 2>/dev/null || exit 0 #suppress exit status | |
| cat file.txt || exit 0 | |
| #suppress the error silently | |
| $ cat filedoesnotexist.txt && echo "success: $?" || echo "fail: $?" | |
| cat: filedoesnotexist.txt: No such file or directory | |
| fail: 1 | |
| $ cat filedoesnotexist.txt || true && echo $? | |
| cat: filedoesnotexist.txt: No such file or directory | |
| 0 | |
| $ fslint /tmp #lists the duplicate files | |
| $ rdfind /tmp #delete the duplicates,remove the newer files. | |
| $ rdfind -dryrun true /tmp #only report the changes | |
| $ rdfind -deleteduplicates true /tmp | |
| $ cksum *.html #computes checksums for files | |
| $ find . -name "*.html" -exec cksum {} \; #search files by name or type and run the cksum command. | |
| $ find . -name "not_existing_file" | |
| $ echo $? | |
| ----------------------------------------------------------------------------------------------------- | |
| bash -x # runs the script <file> with tracing of each command executed | |
| bash -x -c ls -lai #run a command in BASH, use -c option | |
| test -x <file> #tests whether <file> has execute permissions for the current user | |
| ------------------------------------------------------------------------------------------ | |
| #print variable | |
| export BRANCH_NAME="main" | |
| echo "BRANCH_NAME is..: $BRANCH_NAME" | |
| ------------------------------------------------------------------------------------------ | |
| yum/apt install chrony | |
| systemctl stop chronyd | |
| chronyd -q 'pool pool.ntp.org iburst' | |
| systemctl start chronyd | |
| chronyc tracking #verify | |
| systemctl restart chronyd ; watch chronyc tracking #realtime witnessing | |
| chronyc sources | |
| chronyc sources -v | |
| chronyc | |
| ------------------------------------------------------------------------------------------ | |
| #concatenate strings | |
| export strservice="libvirtd" | |
| echo "${strservice} is still running." | |
| echo $(ls) | |
| echo "The date is $(date)" | |
| echo `pwd` | |
| echo $((3 + (4**3 /2))) #Direct calculation in the shell with echo and $(( ) | |
| ------------------------------------------------------------------------------------------ | |
| #nfs server | |
| exportfs -arv | |
| df -h | |
| cat /etc/exports | |
| # /mnt/nfs_share client_IP_1 (re,sync,no_subtree_check) | |
| echo "$NFS_DIR 192.168.50.7(rw,sync,no_subtree_check)" | sudo tee -a /etc/exports | |
| echo "$NFS_DIR 192.168.50.8(rw,sync,no_subtree_check)" | sudo tee -a /etc/exports | |
| #nfs client mount -t nfs NFS_SERVER_IP:NFS_SERVER_DIR NFS_CLIENT_DIR | |
| mount -t nfs 10.20.20.8:/mnt/backups /mnt/backups | |
| umount /mnt/backups | |
| mount | grep nfs | |
| showmount -e | |
| ------------------------------------------------------------------------------------------ | |
| #execute shell command produced using echo and sed | |
| echo "mv /server/today/logfile1 /nfs/logs/ && gzip /nfs/logs/logfile1" | bash # | |
| bash -c "$(echo "mv /server/today/logfile1 /nfs/logs/ && gzip /nfs/logs/logfile1")" #pass it as an argument to a shell | |
| eval "$(echo "mv /server/today/logfile1 /nfs/logs/ && gzip /nfs/logs/logfile1")" #use the bash built-in eval | |
| ------------------------------------------------------------------------------------------ | |
| $ mycommand="wc -l department.txt" | |
| $ eval $mycommand | |
| ------------------------------------------------------------------------------------------ | |
| $ cat /proc/sys/net/ipv4/ip_local_port_range | |
| ------------------------------------------------------------------------------------------ | |
| #redirection is done by the shell which doesn't has write permission | |
| sudo echo 1 > /proc/sys/net/ipv4/ip_forward | |
| bash: /proc/sys/net/ipv4/ip_forward: Permission denied | |
| echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward #resolution-1 | |
| $ sudo sh -c 'echo 1 > /proc/sys/net/ipv4/ip_forward' #resolution-2 | |
| $ sudo -s #resoluton-3 | |
| # echo 1 > /proc/sys/net/ipv4/ip_forward | |
| $ cat testscript.sh #resolution-4 | |
| #!/bin/sh | |
| echo 1 > /proc/sys/net/ipv4/ip_forward | |
| sudo echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward > /dev/null #same | |
| $ sudo tee /proc/sys/net/ipv4/ip_forward > /dev/null << EOF #same | |
| 1 | |
| EOF | |
| ------------------------------------------------------------------------------------------ | |
| #source tar build, no version typing | |
| tar zfx rrdtool.tar.gz | |
| cd rrdtool-* | |
| ------------------------------------------------------------------------------------------ | |
| echo 1 > /proc/sys/kernel/sysrq;echo f > /proc/sysrq-trigger;echo 0 > /proc/sys/kernel/sysrq #Trigger Out Of Memory (OOM) killer without reboot | |
| ------------------------------------------------------------------------------------------ | |
| ls -la .mozilla/firefox #user preferences,browser cookies,bookmarks,browser cache content etc. | |
| ------------------------------------------------------------------------------------------ | |
| #troubleshooting memory problems | |
| #Suddenly killed tasks are often the result of the system running out of memory, when the so-called Out-of-memory (OOM) killer steps in | |
| $ grep -i -r 'out of memory' /var/log/ #search the logs for messages of out of memory alerts | |
| $ free -m #megabytes | |
| $ free -m |head -n 2 |tail -n 1 |awk '{free=($4); print free}' | |
| $ top | |
| $ top -i -u vagrant #ignore idle processes | |
| $ top -n 1 -o RES | grep kvm | |
| $ uptime | |
| #"system load averages" that show the running thread (task) demand on the system as an average number of running plus waiting threads. | |
| #show three averages, for 1, 5, and 15 minutes | |
| #If the averages are 0.0, system is idle | |
| #If the 1 minute average is higher than the 5 or 15 minute averages, then load is increasing | |
| #If the 1 minute average is lower than the 5 or 15 minute averages, then load is decreasing. | |
| $ ps -aylC $APACHE |grep "$APACHE" |awk '{print $8'} |sort -n |tail -n 1 | |
| $ ps -eL h -o state | egrep "R|D" | wc -l #The instantaneous number of such tasks | |
| #Linux load average,the instantaneous load of a system the number of tasks (processes and threads) | |
| #that are willing to run at a given time t | |
| #either in state R or D, either actually running or blocked on some resource (CPU, IO, ...) waiting for an opportunity to run | |
| $ cat /proc/sys/vm/swappiness | |
| #The Linux kernel moves out pages which are not active or being used at the moment to swap space on the disk. This process is known as swappiness. | |
| #turn off swaping by changing t he value in /proc/sys/vm/swappiness to 0.The value ranges from 0 to 100 whe re 100 means aggressive swapping | |
| vmstat –a 1 99 #show memory usage information | |
| vmstat -n 1 # If 'si' and 'so' (stands for swapin and swapout) fields are always 0, then the system is currently not swapping | |
| $ grep DirectMap /proc/meminfo | |
| $ cat /proc/meminfo #Relevant fields from /proc/meminfo to match them against the output of free -k | |
| MemTotal — Total amount of physical RAM, in kilobytes. | |
| MemFree — The amount of physical RAM, in kilobytes, left unused by the system. | |
| Buffers — The amount of physical RAM, in kilobytes, used for file buffers. | |
| Cached — The amount of physical RAM, in kilobytes, used as cache memory. | |
| SwapCached — The amount of swap, in kilobytes, used as cache memory. | |
| Active — The total amount of buffer or page cache memory, in kilobytes, that is in active use. This is memory that has been recently used and is usually not reclaimed for other purposes. | |
| Inactive — The total amount of buffer or page cache memory, in kilobytes, that are free and available. This is memory that has not been recently used and can be reclaimed for other purposes. | |
| HighTotal and HighFree — The total and free amount of memory, in kilobytes, that is not directly mapped into kernel space. The HighTotal value can vary based on the type of kernel used. | |
| LowTotal and LowFree — The total and free amount of memory, in kilobytes, that is directly mapped into kernel space. The LowTotal value can vary based on the type of kernel used. | |
| SwapTotal — The total amount of swap available, in kilobytes. | |
| SwapFree — The total amount of swap free, in kilobytes. | |
| Dirty — The total amount of memory, in kilobytes, waiting to be written back to the disk. Writeback — The total amount of memory, in kilobytes, actively being written back to the disk. | |
| Mapped — The total amount of memory, in kilobytes, which have been used to map devices, files, or libraries using the mmap command. | |
| Slab — The total amount of memory, in kilobytes, used by the kernel to cache data structures for its own use. | |
| Committed_AS — The total amount of memory, in kilobytes, estimated to complete the workload. This value represents the worst case scenario value, and also includes swap memory. PageTables — The total amount of memory, in kilobytes, dedicated to the lowest page table level. | |
| VMallocTotal — The total amount of memory, in kilobytes, of total allocated virtual address space. | |
| VMallocUsed — The total amount of memory, in kilobytes, of used virtual address space. | |
| VMallocChunk — The largest contiguous block of memory, in kilobytes, of available virtual address space. | |
| HugePages_Total — The total number of hugepages for the system. The number is derived by dividing Hugepagesize by the megabytes set aside for hugepages specified in /proc/sys/vm/hugetlb_pool. This statistic only appears on the x86, Itanium, and AMD64 architectures. | |
| HugePages_Free — The total number of hugepages available for the system. This statistic only appears on the x86, Itanium, and AMD64 architectures. | |
| Hugepagesize — The size for each hugepages unit in kilobytes. By default, the value is 4096 KB on uniprocessor kernels for 32 bit architectures. For SMP, hugemem kernels, and AMD64, the default is 2048 KB. For Itanium architectures, the default is 262144 KB. This statistic only appears on the x86, Itanium, and AMD64 architectures. | |
| Matching output of free -k to /proc/meminfo | |
| free output coresponding /proc/meminfo fields | |
| Mem: total MemTotal | |
| Mem: used MemTotal - MemFree | |
| Mem: free MemFree | |
| Mem: shared (can be ignored nowadays. It has no meaning.) N/A | |
| Mem: buffers Buffers | |
| Mem: cached Cached | |
| -/+ buffers/cache: used MemTotal - (MemFree + Buffers + Cached) | |
| -/+ buffers/cache: free MemFree + Buffers + Cached | |
| Swap: total SwapTotal | |
| Swap: used SwapTotal - SwapFree | |
| Swap: free SwapFree | |
| ------------------------------------------------------------------------------------------ | |
| cat newpass.txt | chpasswd #update passwords in batch mode | |
| echo 'ubuntuser:ubuntupassword' | sudo chpasswd | |
| $cat > pass.txt | |
| user1:user1_password | |
| user2:user2_password | |
| user3:user3_password | |
| $chpasswd < file_name.txt | |
| CURRENT_USERS=$(who) #Assign Output of a Linux Command to a Variable | |
| ------------------------------------------------------------------------------------------ | |
| ls -1 #list one file per line,vertically using the -1 switch | |
| ------------------------------------------------------------------------------------------ | |
| sudo !! #Re-Run Last Executed Command as Root User, “sudo” followed by a space and two exclamation points. | |
| ------------------------------------------------------------------------------------------ | |
| #If set, sudo will only run when the user is logged in to a real tty | |
| #sudo can only be run from a login session and not via other means such as cron(8) or cgi-bin scripts | |
| #enable sudo within scripts | |
| sudo /usr/sbin/visudo | |
| $ cat /etc/sudoers | |
| Defaults:username !requiretty #Disable requiretty to particular user | |
| #sudoers file allows both artbristol and bob to execute /path/to/program as root from a script | |
| #artbristol needs no password whereas bob must have to enter a password | |
| artbristol ALL = (root) NOPASSWD: /path/to/program | |
| bob ALL = (root) /path/to/program | |
| Defaults!/path/to/program !requiretty | |
| #allows artbristol to run /path/to/program --option in a script, but not /path/to/program with other arguments. | |
| Cmnd_Alias MYPROGRAM = /path/to/program --option | |
| artbristol ALL = (root) /path/to/program | |
| artbristol ALL = (root) NOPASSWD: MYPROGRAM | |
| Defaults!MYPROGRAM !requiretty | |
| ------------------------------------------------------------------------------------------ | |
| #This allows the source (the sending host) to specify the route, loosely or strictly, ignoring the routing tables of some or all of the routers | |
| #source-based routing should be disabled. | |
| /sbin/sysctl -w net.ipv4.conf.all.accept_source_route=0 #drop packets with the SSR or LSR option set | |
| #Disabling the forwarding of packets should also be done in conjunction with the above when possible (disabling forwarding may interfere with virtualization) | |
| /sbin/sysctl -w net.ipv4.conf.all.forwarding=0 | |
| /sbin/sysctl -w net.ipv6.conf.all.forwarding=0 | |
| #These commands disable forwarding of all multicast packets on all interfaces | |
| /sbin/sysctl -w net.ipv4.conf.all.mc_forwarding=0 | |
| /sbin/sysctl -w net.ipv6.conf.all.mc_forwarding=0 | |
| #Accepting ICMP redirects has few legitimate uses. Disable the acceptance and sending of ICMP redirected packets unless specifically required | |
| /sbin/sysctl -w net.ipv4.conf.all.accept_redirects=0 | |
| /sbin/sysctl -w net.ipv6.conf.all.accept_redirects=0 | |
| #disables acceptance of secure ICMP redirected packets on all interfaces | |
| /sbin/sysctl -w net.ipv4.conf.all.secure_redirects=0 | |
| # disables acceptance of all IPv4 ICMP redirected packets on all interfaces: | |
| /sbin/sysctl -w net.ipv4.conf.all.send_redirects=0 | |
| #automatically disable sending of ICMP requests whenever you add a new interface | |
| /sbin/sysctl -w net.ipv4.conf.default.send_redirects=0 | |
| #make these settings persistent across reboots, modify the /etc/sysctl.conf file | |
| #disable acceptance of all IPv4 ICMP redirected packets on all interfaces, | |
| #open the /etc/sysctl.conf file with an editor running as the root user and add a line as follow | |
| net.ipv4.conf.all.send_redirects=0 | |
| ------------------------------------------------------------------------------------------ | |
| #Reverse Path Forwarding is used to prevent packets that arrived through one interface from leaving through a different interface | |
| #unless you know that it is required, it is best enabled as it prevents users spoofing IP addresses from local subnets and reduces the opportunity for DDoS attacks. | |
| #permanent changes can be made by adding lines to the /etc/sysctl.conf | |
| # make a temporary global change | |
| sysctl -w net.ipv4.conf.default.rp_filter=integer | |
| sysctl -w net.ipv4.conf.all.rp_filter=integer | |
| ------------------------------------------------------------------------------------------ | |
| #Enabling Packet Forwarding | |
| #enable packets arriving from outside of a system to be forwarded to another external host | |
| #change the line which reads net.ipv4.ip_forward = 0 in the /etc/sysctl.conf file to the following | |
| net.ipv4.ip_forward = 1 | |
| /sbin/sysctl -p #load the changes from the /etc/sysctl.conf file | |
| /sbin/sysctl net.ipv4.ip_forward #check if IP forwarding is turned on,If it returns 1, then IP forwarding is enabled | |
| /sbin/sysctl -w net.ipv4.ip_forward=1 #If it returns 0, turn it on manually | |
| ------------------------------------------------------------------------------------------ | |
| #check public IP,private (viewable within an internal network) or public (can be seen by other machines on the Internet) | |
| #3rd party web-sites | |
| $ wget -qO- http://ipecho.net/plain | xargs echo | |
| $ curl ifconfig.co | |
| $ curl ifconfig.me | |
| $ curl icanhazip.com | |
| $ curl -4 icanhazip.com | |
| $ curl -6 icanhazip.com | |
| $ curl ident.me | |
| $ curl checkip.dyndns.org | |
| $ curl api.ipify.org | |
| $ curl ipinfo.io/ip | |
| $ curl checkip.amazonaws.com | |
| ------------------------------------------------------------------------------------------ | |
| #The Internet Assigned Numbers Authority (IANA) has assigned several address ranges to be used by private networks | |
| Class A: 10.0.0.0 to 10.255.255.255 | |
| Class B: 172.16.0.0 to 172.31.255.255 | |
| Class C: 192.168.0.0 to 192.168.255.255 | |
| Class A: 10.0.0.0/8 (255.0.0.0) | |
| Class B: 172.16.0.0/12 (255.240.0.0) | |
| Class C: 192.168.0.0/16 (255.255.0.0) | |
| ------------------------------------------------------------------------------------------ | |
| #Running GUI applications as root | |
| sudo /usr/bin/etherape | |
| ------------------------------------------------------------------------------------------ | |
| chage -l ubuntu #last password change date | |
| ------------------------------------------------------------------------------------------ | |
| #read first, and if a match is found the connection is allowed and the search is stopped. | |
| #If no allowed match if found, the hosts.deny file is read | |
| /etc/hosts.allow | |
| #If a match is found the connection is refused - otherwise it is allowed | |
| #/etc/hosts.deny | |
| ------------------------------------------------------------------------------------------ | |
| # print server's IP on the wellcome page | |
| echo $(ifconfig eth0 | grep 'inet addr' | awk -F: '{ print $2 }' | awk '{ print $1 }') >> /var/www/html/index.html | |
| ------------------------------------------------------------------------------------------ | |
| getfacl -a a.txt #file access control list of a file or directory. | |
| getfacl -t a.txt | |
| getfacl -n file #numeric user and group IDs | |
| getfacl -d a.txt #the default access control list of a file or directory. | |
| getfacl -R directory # the ACLs of all files and directories recursively (sub-directories) | |
| getfacl -L -R directory #follow symbolic links to directories. The default behavior is to follow symbolic link arguments and skip symbolic links encountered in subdirectories | |
| getfacl -P -R directory #do not follow symbolic links to directories,skip symbolic link arguments | |
| setfacl -m u:deepak:rw a.txt #grant read and write permission | |
| setfacl -b a.txt #remove all extended ACL entries,remove all entries | |
| setfacl -x u:deepak a.txt #remove user | |
| setfacl -x g:linux file #remove group | |
| setfacl -m g:linux:rw -R directory #remove group recursively (sub-directories) | |
| setfacl -k file #remove the default access control list | |
| setfacl --test -x g:linux -R dir1 #The ACLs are not modified in test mode. It only displays the changes that will take place | |
| setfacl -dm "user:my_user:r--" /path/to/directory #Add a default entry to grant access to the user my_user on all newly created files within a directory | |
| getfacl file1 | setfacl --set-file=- file2 #copy the ACL of one file to another | |
| ------------------------------------------------------------------------------------------ | |
| for i in *linux*; do rm $i; done #delete all the files in the current directory that contains the word “linux” | |
| cat linux.txt | grep n #list the entries that start has the character ‘n’ | |
| cat linux.txt | grep ^a #ist the entries that start with the character ‘a’ | |
| echo "shutdown now" | at -m 18:00 #shut down the system at 6 pm today | |
| vim -R <filename> #open a file in read-only mode | |
| vim +/<employee id to be searched> <filename> #search for a specific Employee ID in a file | |
| ------------------------------------------------------------------------------------------ |
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