Linux Commands

Vishal Vyas

Linux Commands

This is a list of commands that gives you just enough information to decide what command you want to use.

A

• alias – allows you to create shorter or more familiar names for commonly used commands
• apropos – search the manual page names and descriptions
• at – execute a command-line task at a specified future time
• awk – print only the n^th word of an input line and more

B

• badblocks – a command disk utility
• bash – a shell
• beep – customized audible alerts
• bunzip2 – unpack files packed with bzip2
• bzip2 – a pack utility

C

• cat – receive strings from stdin or a file and output them to stdout or a file
• chgrp – change the group ownership of a file
• chmod – change the permission mode of a file
• chown – change the owner of a file
• chroot – change the position of a root directory in filesystem
• chsh – change the shell of a user
• cp – copy a file
• cpio – pack or unpack files in cpio archives or tarballs
• cron – schedule tasks to be executed regularly at a specific time
• crontab – control the cron service
• cut – display specific coloumns of a file delimited by a character
• cvs – a version management system

D

• date – output or set date and time
• dd – dump a disk to/from a file and more
• df – show how much free disk space there is
• diff – show the difference between two files and more
• dig – show answer of DNS lookup of queried name server
• disown – disowns a job (removes the pid of the job). Even when the shell exits, the job won’t stop running
• du – show how much disc space is used up

E

• echo – echo a string/value to stdout
• env – show all environment variables
• exit – exit most shells
• export – set an environment variable in the bash or zsh

F

• fdisk – partition a disc
• fg – fetch a process from the background to the foreground
• file (command) – determine a file’s type
• find – find a file depending on its name, size, change date or other attributes
• ftp – get files from the internet

G

• g++ – compile C++ code
• gcc – compile C code
• grep – grab for patterns in a file and more
• groups – show what groups your user is in
• gunzip – unpack files from a special format
• gzip – pack files in a special format

H

• halt – shut down your computer
• head – show only the first n lines of a file and more
• hexdump – show a file’s content in hexadecimal numbers and more
• history (command) – show a command history in the bash shell
• hostname – show your computer’s name
• hwinfo – show your available hardware

I

• id – show your user and groups ids
• ifconfig – show your ip address and more
• info – show info about a given command
• init – reboot or change runlevel
• iptables – show your firewall configuration
• iptraf – Interactive IP LAN monitor

J

• jobs – gives a list of current background jobs (processes)

K

• kill – kill a process
• killall – kill all processes with a given name

L

• ldd – show dynamic libraries needed by an executable
• less – show output in a viewer where you can scroll and search
• ln – link a file
• ls – list a file
• lsmod – list loaded kernel modules
• lsof – list open files and listening sockets
• lspci – list all pci devices
• lsusb – list usb devices

M

• make – compile software and more
• man – get help on questions that you never wanted to ask
• md5sum – compute the md5 sum of a file and more
• mkdir – make a directory
• mkfs – format a device
• minicom – communicate over your RS232 interface
• more – show input in a searchable pager
• mount – prepare a device for reading and writing
• mv – move a file (can also be renaming)

N

• netcat – Send some bytes to the network
• netstat – get information on listening sockets, open ports and more
• nice – set a process’ priority
• nm – list the names of functions in an object file
• nmap – network and port scanner tool

O

• objdump – show information about object files
• openssl – create cryptographic server certificates and more

P

• passwd – change your and other’s password
• ping – show if a given computer is up and running
• ps – show running processes
• pwd – show your current working directory

Q

• quota – manage how much resources the user is allowed to consume

R

• rar – rar files/directories
• read – read a string from your keyboard and more
• reboot – reboot the computer
• rename – rename a file
• rm – delete a file
• route – manage your network routing table
• rpm – a package management backend for Redhat and Fedora
• rsync – synchronize your folders over the network

S

• scp – (secure copy) over a network
• screen – a terminal multiplexer
• sed – manipulate a stream of characters (scripting language)
• setenv – change the value of an environment variable in the csh
• shuf – generate random permutations
• shutdown – shutdowns/reboots the system
• sleep – wait/delay some time
• ssh – login into / execute commands in a remote host
• su – change user
• sudo – execute the command as another user (usually root- /etc/sudoers)

T

• tail – show only the last n lines of a file and more
• tar – pack files in a special format
• tcpdump – dump the tcp network traffic
• tee – multiplex cli output
• time – show the time needed by a command to finish
• top – show the top CPU consuming processes and more
• touch – create a file or update its time stamp
• traceroute – show the route a package takes over the network
• tac – print the file in reverse. (opposite of cat) (cat X tac)

U

• ulimit – show the limits of your user
• umount – unmount a device (Often requires sudo permissions)
• uname – show the running kernel’s version and more
• uniq – remove repeated lines in a sorted file
• unzip – unpack files
• uptime – show the time since your computer was last switched on
• useradd – add a user
• userdel – delete a user
• usermod – modify a user

V

• Vgcreate – create lvm volume groups
• Vgdisplay – display lvm volume groups
• Vgs – show information about lvm volume groups
• Vgscan – scan for lvm volume groups
• vim – its not a text editor like Notepad, it is an IDE
• Vmstat – show input/output values, swap, memory consumption and more

W

• w – print who is logged in to your system
• wc – word count (word,line,char)
• which – print the path where you find an executable file
• whoami – print your effective user name

X

• xargs – hand over stdin as a parameter
• xev – show information about your keystrokes and more
• xkill – kill a window that is in your way
• xosview – show CPU/memory/hard Drive activity and more

Y

• yacc – A C parser generator
• yes – repeatedly output a string
• yum – a package management frontend for Redhat & Fedora
• yast – a package management frontend for SUSE

Z

• zip – pack a file