Ubuntu essential commands

Ubuntu essential Commands

Doesn't matter how good programmer, system administrator or technologist you are. You always have to refer to online documentation or I say ask GOOGLE to recall
those commands. It pisses me a lot. I created this GIST to refer too, whenever I am stuck.

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Privileges Management
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$sudo :– run command as root
$sudo -s :– open a root shell
$sudo -i :-similar to sudo su - , gives you roots environment configuration
$sudo -s -u user name              : – open a shell as user
$sudo -k :–forget sudo passwords
$gksudo command :– visual sudo dialog (GNOME)
$kdesudo command :– visual sudo dialog (KDE)
$sudo visudo :– edit /etc/sudoers
$gksudo nautilus :– root file manager (GNOME)
$kdesudo konqueror :– root file manager (KDE)
$passwd :– change your password
Note:- By default sudo remembers your password for 15 minutes. If you want to change that you can do so by
deepak@ubuntu:~$ sudo vim /etc/sudoers :-Add ,timestamp_timeout=X next to env_reset. After editing your file may look like this
....................................................
# See the man page for details on how to write a sudoers file.
#
Defaults env_reset,timestamp_timeout=60
# Host alias specification
.......................................................................................................................................
X indicate time in minutes. 0 means you need to type evey time when you use sudo. negative value meanes you need to type password again.

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Networking Management
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$ifconfig  :– show network information
$iwconfig :-–show wireless information
$sudo iwlist scan :– scan for wireless networks
$sudo /etc/init.d/networking restart :– reset network for manual configurations
$ifup :– bring interface online
$ifdown :– disable interface 
$ping :-  convert names to IP addresses and vice versa
$host  name convert names to IP addresses and vice versa
$nslookup :-nslookup is a program to query Internet domain name servers
$dhclient eth0 :- active interface 'eth0' in dhcp mode
$ethtool eth0 :- show network statistics of eth0
$hostname :- show hostname of system   [man]
$ifconfig eth0 192.168.1.1 netmask 255.255.255.0 :- configure IP Address
$ifconfig eth0 promisc :- configure 'eth0' in promiscuous mode to gather packets (sniffing)
$ip link show :- show link status of all network interfaces
$iwlist scan :- wifi scanning to display the wireless connections available
$netstat -tup :- show all active network connections and their PID
$netstat -tupl :- show all network services listening on the system and their PID
$netstat -rn :- show routing table alike "route -n"
$route -n :- show routing table
$route add -net 0/0 gw IP_Gateway :- configure default gateway
$route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1 :- configure static route to reach network '192.168.0.0/16'
$route del 0/0 gw IP_gateway :- remove static route
$tcpdump tcp port 80 :- show all HTTP traffic

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Dispaly Management
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$sudo /etc/init.d/gdm restart :– restart X and return to login (GNOME)
$sudo /etc/init.d/kdm restart :– restart X and return to login (KDE)
$cat /etc/X11/xorg.conf :– display configuration
$sudo dexconf :– reset xorg.conf configuration
Ctrl+Alt+Bksp :– restart X display if frozen
Ctrl+Alt+FN :– switch to tty N
Ctrl+Alt+F7 :-– switch back to X display

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Services Management
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Essentials services ( networking, mysql, apache2, vsftpd, ssh, nginx )

$sudo  /etc/init.d/servicename start :– start service
$sudo /etc/init.d/servicename stop :– stop service
$sudo /etc/init.d/servicename status :– check service
$sudo /etc/init.d/servicename restart :-– restart service
$sudo sysv-rc-conf  servicename  on :-Enabling a service at boot
$sudo sysv-rc-conf  servicename  off :- Disabling a service at boot
$sudo update-rc.d  servicename  defaults :- Enabling a service at boot
$sudo update-rc.d  servicename  purge :- Disabling a service at boot
$runlevel  :– get current runlevel

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Package Management
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$sudo apt-get update :– refresh available updates
$sudo apt-get upgrade :– upgrade all packages
$sudo apt-get dist-upgrade :– upgrade with package replacements; upgrade Ubuntu version
$sudo apt-get install  packagename :– install pkg
$sudo apt-get remove packagename --purge :- Remove packgege with configfiles
$sudo apt-get autoremove :– remove obsolete packages
$sudo apt-get -f install :– try to fix broken packages/unresolved dependencies
$sudo apt-get clean :-apt-get clean removes everything except lock files from /var/cache/apt/archives/ and /var/cache/apt/archives/partial/
$sudo apt-get autoclean :-apt-get autoclean removes only package files that can no longer be downloaded.
$sudo apt-cache search packagename  :- search a packages
$sudo apt-cache show packagename :- get information about a packges
$sudo apt-cache depends packagename :- get package dependency
$sudo apt-file list packagename :- get file names in a package
$sudo apt-file search filename :- discovers the package file belong to
$sudo apt-file updatelong :- apt-file keeps a database of which files all packages contain, just like auto-apt does and it needs to be up-to-date. This is done by running
$sudo apt-get source packagename :-download a source of package
$sudo dpkg --configure -a – try  :-to fix broken packages
$sudo dpkg -l :-get installed package list
$sudo dpkg -l packagename :- Query version of package and if package is installed.
$sudo dpkg -L packagename :- List all files on the system associated with the package.
$sudo dpkg -S filename :- List the package name to which this file is associated.
$sudo dpkg -p filename :- Print package information. See /var/lib/dpkg/available
$sudo dpkg -i packagename.deb :- Install package.
$sudo dpkg -r packagename :- Remove package. Keep configuration files.
$sudo dpkg -P packagename Remove package. Remove configuration files.

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File Management
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$vim  filename  :-Vi fullscreen editor
$wc  filename  :-Line, word, & char count
$cat filename  :- List contents of file
$more filename  :-List file contents by screen
$cat file1 file2 > file3  :-Concatenates file1 & file2 into file3
$chmod mode file  :-Change protection mode of f
$cmp file1 file2  :-Compare two files
$cp file1 file2 :-Copy file file1 into file2
$sort file  :- Alphabetically sort file
$split [-n]  file  :-Split file into n-line pieces
$mv file1  file2 :- Rename file file1 as file2
$rm file1  :-Delete (remove) file file1
$grep ‘ptn’ file  :-Outputs lines that match ptn
$diff file1 file2    :-Lists file differences
$head file  :-Output beginning of file
$tail file    :-Output end of file

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Environment Management
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$cd dir1     :- Change to directory dir1
$mkdir dir1 :- Create new directory dir1
$rmdir dir1 :- Remove directory dir1
$mv file1 [file2...] dir :- Move file f to directory dir
$mv dir1 dir2  :- Rename directory dir1 as dir2
$passwd :- Change password
$alias name1 name2 :- Create command alias
$unalias name1 :- Remove command alias name1
$logout :- End terminal session
$setenv name var :- Set env var to value var
$unsetenv name1 name2...]  :- remove environment variable
$ls [d] [file]  :- List files in directory
$ls -1 [file]  :- List files in detail
$alias [name] :- Display command aliases
$printenv [name] :- Print environment values
$quota :- Display disk quota
$date :-Print date & time
$who :- List logged in users
$whoami :- Display current user
$finger [username] :- Output user information
$chfn :- Change finger information
$pwd :- Print working directory
$history :- Display recent commands
$! n :- Submit recent command n