This Linux cheat sheets are intended to give a list of most useful bash commands and utilities. They will be divided as four main sheets: a general list, a list for sys admin, a list for networking, and a list for bash scripting utilities

myLinuxCheatSheet

==============================================Basic Comands===============================================



cat FILE				Displays FILE's content (moves FILE content to standard output,
					hence, if multiple files are specified, it concatenates them all)
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cat > FILE				Creates/overrides FILE's content with standard input
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cd DIR					Moves to DIR directory
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cp FILE DEST				Copies file FILE to DEST
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cp DIR/{FILE1,FILE2,...,FILEN} DEST	Copies files from FILE1 to FILEN to DEST
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cp -R DIR DEST				Copies DIR directory and it's content to DEST
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echo TEXT				Prints TEXT
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find DIR -name FILE -type TYPE		Find all the files named like FILE of the type TYPE 
					(d,c,f,b,p,l,s) from DIR directory and ahead (sublevels, never 
					goes to upper levels from DIR) 				
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grep PATT FILE				Search PATT pattern in FILE and displays all the lines which 
					contain it. Usually used with a pipe, example: CMD | grep PATT 
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gzip FILE 				Compress FILE into FILE.gz; original file IS NOT kept (use
					-k flag if you wish to keep it)
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gzip -d FILE				Decompress FILE (must be a valid gz file). You can use 
					'gunzip' instead, it will reproduce same result
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head FILE				Shows first 10 lines of FILE
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history					Shows your history of used commands
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jobs -l 				Displays current jobs
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less FILE				Displays FILE's content in a paginted way (is more than more)
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ls -alFh DIR				Displays contents of DIR directory, including hidden files (a),
					With details as a list (l), differentiating regular files from
					directories (F), and showing human readable byte amounts (h)
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more FILE				Displays File's content in a paginated way  			
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mkdir -p DIR/INNERDIR			Creates DIR directory and INNERDIR directory (optional)
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mv FILE DEST				Moves file FILE to DEST
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mv DIR/{FILE1,FILE2,...,FILEN} DEST	Moves files from FILE1 to FILEN to DEST
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mv -R DIR DEST				Moves DIR directory and it's content to DEST
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pwd					Displays current working directory
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pushd DIR				Pushs DIR directory to a directory stack 
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popd					Pops out an element from the directory stack 
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rm -R DIR				Deletes DIR directory and it's content
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rmdir DIR				Deletes DIR directory. (MUST BE EMPTY)
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rm FILE					Deletes FILE file 
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tar -cvzf TARNAME FILE			Compress(-c) and zips(-z) the specified (with -f) FILE file 
					or directory into the TARNAME file (must be '*.tar.gz' or 
					'*.tgz'). For just compressing FILE, use -cvf options and use 
					.tar extension in TARNAME.
					NOTE: 'f' option must be in last place
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tar -tvf TARNAME			Displays(-t) TARNAME's content (must be a valid tar file)
					NOTE: 'f' option must be in last place
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tar -xvf TARNAME 			Extracts(-x) TARNAME's content in current directory. If you
					wants to extract to a different directory, add
					"-C DIR" option, where DIR is a valid directory
					NOTE: 'f' option must be in last place
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tail FILE				Shows last 10 lines of FILE
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touch FILE				Creates an empty file with FILE name
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vim FILE				Creates/opens FILE in VIM editor to edit it's content 
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./FILE 					Executes FILE 




===============================================Admin tools================================================



cut -d "DEL" -f "1,2,...,N" FILE	Splits each line of FILE into columns defined by DEL separator
					(delimiter), and displaying only the columns specified by -f 	
					parameter 
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chgrp GRP FILE				Changes default group of FILE to GRP				
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chmod PERM FILE				Changes system security permissions of FILE to PERM (bits or 
					letters)
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chown OWN FILE 				Changes the default owner of FILE to OWN
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df -h 					Lists filesystems information with human readable amounts (-H).
					This includes hardrives and external drives (such as USB)
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eject /dev/DEVICE			Unmounts and eject the specified DEVICE device
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env 					Displays all environment variables
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export VAR=HUE				Define VAR variable with HUE value and make it part of
					environment (just for your current shell and subsequents 
					subshells)
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free -h 				Shows memory stats with human readable amounts (-h)
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groups USER				Displays the groups to which USER belongs to (default $USER)
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gpasswd -a USER GRP			Adds USER user to GRP group
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gpasswd -d USER GRP 			Deletes USER user from GRP group
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id USERID				Displays user and group information of specified USERID id 
					(default $UID)
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kill -9 PID				Sends a SIGKILL signal to the process with the PID id. ( SIGKILL
					instantly terminates the process) 
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killall -9 PNAME			Sends a SIGKILL signal to the process with the PNAME name.
					(SIGKILL instantly terminates the process)
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lsusb 					Displays information about USB buses and connected USB devices
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man CMD 				Displays manual pages for CMD
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passwd USER 				Changes/sets a new password for USER user
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ps -fea					Displays current status from all running processes
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sed 's/PATT/REP/g' FILE			Replaces every instance in FILE that match PATT pattern 
					(can be a regex) with REP text
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shutdown -h TIME 			Shutdown the computer at TIME (use 'now' for instant shutdown)
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shutdown -r TIME			Reboot the computer at TIME (use 'now' for instant reboot)
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su USER					Login as USER (default is 'root' user)
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sudo USER CMD				Executes CMD as USER (default is 'root' user)
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top 					Displays a real-time stats of the system running information

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type CMD				Displays where CMD executable file is or if it's a built-in 
					shell command
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useradd -m -U USER			Creates a new user named USER, and a group with the same 
					name (-U). It also creates the user's home directory (-m).
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userdel -f USER				Deletes USER user, it's mailing pool and it's home directory
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usermod -aG GRP USER			Adds USER user to GRP group
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which CMD				Displays where CMD executable file is located
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who -H 					Displays users logged in, with heading information (H)
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whoami					Displays your username (same as echo $USER)




=============================================Networking tools=============================================



curl -X METH -d "DATA" -H"Head" URL	Sends a request to URL using the METH (POST, GET, etc.)
					method and the HEAD header, providing DATA as part of the body
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iftop -i INTERFACE			Shows network stats in specified INTERFACE
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lsof -i :PORT				Shows real-time process and network information about 
					the resources using the specified PORT
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nethogs INTERFACE			Shows real-time network stats about processes using the 
					specified network interface INTERFACE (default is all of them)  
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netstat --inet -apn			Lists DARPA (ipv4) network connections (--inet), showing all 
					sockets (-a) used, also displaying it's belonging processes (-p)
					without resolving ip directions nor port names (-n)
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nmap -sA NETWORK			Scans the given NETWORK (example, 192.168.1.0/24) looking for
					connected devices
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nmcli con add con-name NAME		Add a new TYPE (ethernet,wifi,etc.) connection for the specified
ifname INTERFACE type TYPE		INTERFACE interface (use * for all), using the given IP/NETMASK
ip4 IP/NETMASK gw4 GATEWAY		and the GATEWAY gateway
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nmcli dev status			Shows network devices status
(nmcli works on Debian and RHEL based)				
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nmcli con down CONNAME			Disconects computer from CONNAME connection
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nmcli con mod CONAME PROP NEW		Modifies CONAME connection, setting PROP property to NEW value
					(to see full list of properties avialable and it's current
					values use 'nmcli con show id CONAME' )
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nmcli con show				Shows avialable network connections (may be down or up)
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nmcli con show id CONAME		Shows profile information about CONAME connection
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nmcli con up CONNAME ifname INTERFACE	Connects computer to CONNAME connection using given INTERFACE
					(default is predefined interface, hence, can be omitted)
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nmcli radio wifi STATE			Changes wifi radio status to STATE ('on' or 'off')
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nslookup URL				Resolves the given URL name into the actual ip address
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ping URL				Sends an ICMP ECHO_REQUEST to the specified URL to elicit an
					ICMP ECHO_RESPONSE from same URL
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route -ve				Shows ip table with verbose(-v) and extended(-e) information
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ssh USER@URL -i PRIVATEKEY		Starts a ssh session with the USER user at the given URL server,
					using the specified (-i) PRIVATEKEY file
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tracepath URL				Traces the route between your computer and the URL server




============================================File descriptors==============================================


0					Standard input (stdin). Regularly keyboard
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1					Standard output (stdout). Regularly display
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2					Standard error (stderr). Regularly display




======================================System security permissions=========================================


a					All
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g					Group
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o					Others
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u					User (owner)
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r					Read ('4' as decimal or '100' as binary)
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w					Write ('2' as decimal or '010' as binary)
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x					Execute ('1' as decimal or '001' as binary)
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LETTER+PERM				Add PERM permission(s) to LETTER group(s) (example, a+rw)
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LETTER-PERM				Removes PERM permission(s) to LETTER group(s) (example, og-r)
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LETTER=PERM				Sets PERM permission(s) to LETTER group(s) (example, u=rwx)
					




===========================================Linux file types===============================================


f ('-')					Regular file
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d 					Directory file
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s					Socket file
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p					Named pipe file
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c 					Character device file
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l					Symbolic link file
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b					block device file





============================================Special operators=============================================


CMD > FILE				Redirects standard output stream to FILE 
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CMD >> FILE 				Redirects and appends standard output stream to FILE
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CMD &> FILE				Redirects standard error and output streams to FILE
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CMD 2> FILE 				Redirects standard error stream to FILE
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CMD 2>> FILE 				Redirects and appends standard error to FILE
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N>&Y					Redirects N stream to Y stream
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CMD < FILE 				Takes FILE as standard input for CMD
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CMD << CONTENT				Takes CONTENT from standard input for CMD 
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CMD &					Executes CMD as a background process (job)
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CMD1 | CMD2				Executes CMD1, then executes CMD2 taking CMD1 output as input 
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(CMD)					Executes CMD in a subshell