List of Linux useful commands

ls  Lists all files and directories in the present working directory

ls -R   Lists files in sub-directories as well

ls -a   Lists hidden files as well

ls -al  Lists files and directories with detailed information like permissions,size, owner, etc.

cd or cd ~  Navigate to HOME directory

cd ..   Move one level up

cd  To change to a particular directory

cd /    Move to the root directory

cat > filename  Creates a new file

cat filename    Displays the file content

cat file1 file2 > file3 Joins two files (file1, file2) and stores the output in a new file (file3)

mv file “new file path” Moves the files to the new location

mv filename new_file_name   Renames the file to a new filename
rm filename Deletes a file

sudo    Allows regular users to run programs with the security privileges of the superuser or root

mv  Renames a directory

ls -l   to show file type and access permission

man Gives help information on a command

clear   Clears the terminal

mkdir directoryname Creates a new directory in the present working directory or a at the specified path

rmdir   Deletes a directory

r   read permission

w   write permission

x   execute permission

-=  no permission

Chown user  For changing the ownership of a file/directory

Chown user:group filename   change the user as well as group for a file or directory

env Displays all environment variables

VARIABLE_NAME= variable_value   Create a new variable
Unset   Remove a variable

export Variable=value   To set value of an environment variable

sudo adduser username   To add a new user

sudo passwd -l ‘username’   To change the password of a user

sudo userdel -r ‘username’  To remove a newly created user

sudo usermod -a -G GROUPNAME USERNAME   To add a user to a group

sudo deluser USER GROUPNAME To remove a user from a group
finger  Shows information of all the users logged in
finger username Gives information of a particular user

SSH username@ip-address or hostname login into a remote Linux machine using SSH

dir Display files in the current directory of a remote computer

cd “dirname”    change directory to “dirname” on a remote computer

put file    upload ‘file’ from local to remote computer

get file    Download ‘file’ from remote to local computer

quit    Logout

ESC Terminate insert mode

u   Undo last change

U   Undo all changes to the entire line

o   Open a new line (goes into insert mode)

i   Insert at cursor (goes into insert mode)

A   Write at the end of line (goes into insert mode)

dd  Delete line

~   Change case of individual character

cw  Change word

S   Substitute entire line and begin to insert at the beginning of the line

R   Overwrite characters from cursor onward