Linux commands

In bash print “hello world”

$ echo "Hello World"

Create directory

$ mkdir testing

Change directory

$ cd testing

List contents inside a directory

$ ls -l

Find logged in user

$ whoami

$ users

$ who

$ w

Find out used disk space in the system by user

$ df -h

Brings the system down immediately

$ halt

Powers off the system using predefined scripts to synchronize and clean up the system prior to shutting down

$ init 0

Reboots the system by shutting it down completely and then restarting it

$ init 6

Shuts down the system by powering off

$ poweroff

Reboots the system

$ reboot

Shuts down the system

$ shutdown

Listing the files

$ ls

Listed files with more information

$ ls -l

List hidden or invisible files

$ ls -a

Create file in Linux

$ vi filename

Display content of a file

$ cat filename

Display file content with line number

$ cat -b filename

Counting words in a file

$ wc filename

Get information about multiple files

$ wc filename1 filename2 filename3

Copying contents from 1 file to another file

$ cp source_file destination_file

Make a copy of existing file

$ cp filename copyfile

Change the name of existing file name

$ mv old_file new_file

Rename the existing file

$ mv filename newfile

Delete a file

$ rm filename

Remove multiple files at a time

$ rm filename1 filename2 filename3

Create symbolic link to a file name

$ ln -s filename symlink

Create hard link to a file name

$ ln filename hardlink

Go to home directory

$ cd ~

Got to user’s home directory

$ cd ~username

Got to last directory

$ cd -

Get current full path

$ pwd

List the files in a directory

$ ls dirname

$ ls /usr/local

Create multiple directory

$ mkdir docs pub

Remove directory

$rmdir dirname

Remove multiple directory

$rmdir dirname1 dirname2 dirname3

Change directory

$ cd dirname

Rename directory

$ mv olddir newdir

Add execute permission of the owner

$ chmod u+x file

Remove write permission from the group

$ chmod g-w file

Set others to read-only (wipes other permissions)

$ chmod o=r file

Give everyone read and write access

$ chmod a+rw file

Add execute permissions for both owner and group

$ chmod ug+x file

Give all permissions

$ chmod 777

Owner can edit, others can run

$ chmod 755

Owner can edit, others can only read

$ chmod 644

Only owner can read/write

$ chmod 600

Read only for owner

$ chmod 400

Change ownership of a file

$ chown user filelist

Changing owner of the file

$ chown amrood testfile

Changing group of the file

$ chgrp developers testfile

Assing a String in a variable and print

$ MESSAGE="I LOVE JESUS"

$ echo $MESSAGE