Linux Cheat Sheet

Basic Linux commands

Command	Description
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	To change to a particular directory
cd ..	Move one level up
cd ~	Navigate to the HOME 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
sudo	Allows regular users to run programs with the security privileges of the superuser or root
rm filename	Deletes a file
man	Gives help information on a command
history	Gives a list of all past commands typed in the current terminal session
clear	Clears the terminal
mkdir directory-name	Creates a new directory in the present working directory or at the specified path
rmdir directory-name	Deletes a directory
mv	Renames a directory
apt-get	Used to install and update packages

Commands	Description
ls -l	to show file type and access permission
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 a group for a file or directory

Command	Description
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
chmod 777 filename	Change the mode of the file to 775
chmod -R 700 filename	Recursively chmod folder to 700

Command	Description
The first digit is owner permission, the second is group and the third is everyone.
Calculate permission digits by adding the numbers below.
4	read (r)
2	write (w)
1	execute (x)

Command	Description
echo $VARIABLE	To display the value of a variable
env	Displays all environment variables
VARIABLE_NAME=variable_value	Create a new variable
Unset	Remove a variable
export Variable=value	To set the value of an environment variable

Command	Description
env	Show environment variables
echo $NAME	The output value of $NAME variable
export $Name=value	Set $NAME to the value
$PATH	Executable search path
$HOME	Home Directory
$SHELL	Current shell

Command	Description
grep -i	Case insensitive search
grep -r	Recursive search
grep -v	Inverted search
grep -o	The show matched part of a file only
find /dir/ -name name*	Find files starting with the name in dir
find /dir/ -user name	Find files owned by name in dir
find /dir/ -mmin num	Find files modified less than num minutes ago in dir
whereis command	Find binary / source / manual for command
locate file	Find the file (a quick search of system index)

Command	Description
top	Details on all Active Processes
ps	Give the status of processes running for a user
ps PID	Gives the status of a particular process
pidof	Gives the Process ID (PID) of a process
kill PID	Kills a process
df	Gives free hard disk space on your system
free	Gives free RAM on your system
nice	Starts a process with a given priority
renice	Changes the priority of an already running process

Command	Description
i	Insert at cursor (goes into insert mode)
a	Write after the cursor (goes into insert mode)
A	Write at the end of the line (goes into insert mode)
ESC	Terminate insert mode
wq	Save & Exit
u	Undo last change
U	Undo all changes to the entire line
o	Open a new line (goes into insert mode)
dd	Delete line
3dd	Delete 3 lines
D	Delete the contents of the line after the cursor
C	Delete the contents of a line after the cursor and insert new text. Press the ESC key to end insertion.
dw	Delete word
4dw	Delete 4 words
cw	Change word
x	Delete the character at the cursor
r	Replace character
R	Overwrite characters from cursor onward
s	Substitute one character under the cursor and continue to insert
S	Substitute the entire line and begin to insert at the beginning of the line
~	Change case of individual character

Thank You,

Abhisek Moharana