Linux Cheat Sheet

Linux Cheat Sheet

List Commands

ls -l    

 list the files and directories in long list format with extra information

ls -a    

 list all including hidden files and directory

ls *.sh  

 list all the files having .sh specific extension.

Change Directory Commands

pwd                 

 present working directory.

cd path_to_directory

 Change directory to the provided path

cd ~ or just cd     

 Change directory to the home directory : /home/ubuntu/

cd ..               

 Change directory to one directory back.

cd ../..            

 Change directory to 2 directory back.

File

touch filename

 Create empty/blank file

touch filename.txt

 Create empty/blank file with extension

touch file{1..100}.txt

 Create 100 text file in one go

touch .file

 Create hidden file

vim filename

 Create and edit the file

cat filename

 See the content of the file

echo "Hello" >> filename.ext

 Print the output message in the file

head -n 3 fruits.txt     

 To see the top 3 lines in fruits.txt

tail -n 3 Colors.txt     

 To see the last 3 lines in Colors.txt

diff fruits.txt Colors.txt

 To see difference between two files

Directory

mkdir DirectoryName         

 To make a directory in a specific location

mkdir .NewFolder            

 make a hidden directory (also . before a file to make it hidden)

mkdir A B C D               

 make multiple directories at the same time

mkdir /home/user/Mydirectory

 make a new folder in a specific location

mkdir -p  A/B/C/D           

 make a nested directory -p = parent

mkdir dir{1..99}            

 To make multiple directories in one go

Remove File and Directory

rm filename

 To remove file

rmdir DirectoryName      

 To remove Empty directory

rmdir -rf DirectoryName  

 To remove a Directory with files in it

System Information

hostname

 Shows the name of the system host.

sudo

 Run commands as security privileges of superuser or root

clear

 Clears the terminal; no old commands on screen

history

 Displays the list of all the typed commands on terminal

whoami

 This command displays the name with which you are logged in.

Create User

sudo useradd username

 Creating new user

sudo useradd -m username

 Creating new user with its home directory

sudo passwd username

 Setting password to user

cat /etc/passwd

 See user info

Delete User

sudo userdel username

 Delete user

sudo userdel -r username

 Delete user with directory of the user

sudo deluser user1 group1

 Remove user from specific group

 Create Goup

sudo groupadd groupname

 Create a group

sudo adduser user123 group123

 Adding user to a group

cat /etc/group

 See group info

sudo usermod -aG docker ubuntu

 Adding ubuntu user in docker group -a append

sudo usermod –aG group1, group2, group3 commonuser

 Add a user to multiple groups at once

Delete Group

sudo groupdel group1

Change Ownership

chown <user_name> <file_name>

 To change file or directory ownership

chgrp <group_name> <file_name>

 To change group ownership

File Permission

chmod <permission> <file_name>

To change permission of the file

chmod 700 file1.txt

 To give rwx permission to owner of the file

chmod u+wx file1.log

 To add read and execute permission for user

chmod ugo+rwx foldername

 To give read, write, and execute to everyone.

chmod a=r foldername

 To give only read permission for everyone.

chmod o-rwx foldername

 To remove read write & exec permission for other

Access Control List

getfacl <file or directory name>

 Get the current permission status

setfacl -m u:abcuser:rwx test/declarations.sh

 To add permission for user -m : modify

setfacl -m g:groupName:permissions /path/to/file

 To add permissions for a group

setfacl -x u:user:w /path/to/file

 To remove write ACL permission of user: -x = remove

Server Level Commands

top

 Get the details of all active processes.

ps

 Give the status of running processes for a user

free -h

 Display the free and used memory; -h  human-readable form

cat /proc/meminfo

 Information about memory like total and occupied

du

 Disk usage of a file or directory