Commonly used linux commands

If you are new to Linux/FreeBSD or linux based OS then you will find that there are some very interesting commands that you use repeatedly. Here is a list of commonly used commands:

Shutdown the operating system

halt
init 0
shutdown -h now

Reboot the operating system

reboot
init 6

Display the manual (man) page for the given command. The must command for mastering Linux/UNIX. If you do not know how to use some command, use man to display its manual page. Remember you can exit a man page by pressing q.

man ls
man man
man date

Switch the current user. If you logged in as vivek and need to change to user account jadmin, then you need to type following command:

su - jadmin

However, this command is mostly used to switch super user account. Just type command su – and you will switch to root user account with its entire environment exported

su -

Display the environment variable:

env

Display a message on the screen or display value of environment variable. For example, display value of HOME variable:

echo $HOME

Setup and export environment variable, for example setup JAVA path with following command:

export PATH=$PATH:/usr/java/bin

Display list of currently running process. To exit top press q

top

Display full path of shell command. For example display full path of gcc command:

which gcc

Display list of logged in users

who

Display what users are doing

w

Display status of network

netstat -r
netstat -nat

Display or setup routing table

route