Linux Commands Cheat Sheet - PCWDLD

There are hundreds – possibly thousands – commands available in Linux. Remembering every command is not possible and it can be quite daunting for a novice user. The good news is that you don't need to remember each command. Only a very small subset of those commands are used on a day-to-day basis.

This cheat sheet offers a set of commands that you can use for quick reference. I have prepared this Linux Commands Cheat Sheet as quick reference for both experienced and basic users.

Basic Linux Commands

In this section, we will show you some basic Linux commands with examples.

Command	Description
hostnamectl	Get system information including, operating system, kernel, and release version
date	Display the current system date and time
hostname	Display the hostname of the system
ifconfig	Display the IP and Mac Address of the system
w	Display currently logged in users in the system
free -m	Display free and used memory in the system
top	Display all running processes
ls	List all files and directories in the current working directory
ls -al	List all files and directories including, hidden files and other information like permissions, size, and owner
cd	Change the directory to the home directory
cd ..	Change the directory to one level up
cat filename	Display the content of the file
cat file1 file2 > file3	Combine two files named file1 and file2 and store the output in a new file file3
tail filename	Display the last 10 lines of a file
head filename	Display the first 10 lines of a file
mv oldfile newfile	Rename a file
rm filename	Delete a file
mkdir dirname	Create a directory
rm -rf dirname	Remove a directory
history	Print a history list of all commands
clear	Clear the terminal
shutdown -h now	Shut down the system
reboot	Restart the system

Networking Commands

Command	Description
ip addr show Or ifconfig	List all IP addresses and network interfaces
ip addr add IP-Address dev eth1	Add a temporary IP address to interface eth1
netstat -pnltu	Display all listening port
whois domainname	Display more information about any domain
dig domainname	Display DNS information of any domain
host domainname	Perform an IP lookup for a domain
dig -x IP-Address	Perform a reverse lookup of an IP address
dig -x domainame	Perform a reverse lookup on domain
ping host-ip	Check connectivity between two hosts

File Permission Commands

Command	Description
ls -l filename	Check the current permission of any file
chmod 777 filename	Assign full(read, write, and execute) permission to everyone
chmod -R 777 dirname	Assign full permission to the directory and all sub-directories
chmod 766 filename	Assign full permission to the owner, and read and write permission to group and others
chmod -x filename	Remove the execution permission of any file
chown username filename	Change the ownership of a file
chown user:group filename	Change the owner and group ownership of a file
chown -R user:group dirname	Change the owner and group ownership of the directory and all sub-directories

User and Group Management Commands

Linux is a multi-user operating system. So multiple users can log in to the system and work on the system at the same time. In some cases, two or more users may need to share access to system resources like files and directories. In that case, user and group management allows you to complete your objectives.

Command	Description
w	Display all login users
useradd username	Add a new user account
userdel -r username	Delete a user account
usermod [option] username	Change the user account information including, group, home directory, shell, expiration date
usermod -aG groupname username	Add a user to a specific group
groupadd groupname	Create a new group
groupdel groupname	Remove a group
last	Display information of the last login user
id	Display UID and GID of the current user

Process Management Commands

When you run any application in Linux. The application will get a process ID or PID. Process Management helps you to monitor and manage your application.

Command	Description
ps	Display all active processes
ps -ef | grep processname	Display information of specific process
top	Manage and display all processes in realtime
pstree	Display processes in the tree-like diagram
lsof	List all files opened by running processes
kill pid	Kill a specific process using process ID
killall processname	Kill all processes by name
bg	Display stopped or background jobs
pidof processname	Get the PID of any process

Disk Management Commands

In this section, we will show you disk management commands including, add and remove partitions, mount a partition, check disk space, format partition, etc.

Command	Description
fdisk -l	List all disk partitions
fdisk /dev/sda	Create a new partition on /dev/sda device
mkfs.ext4 /dev/sda1	Format the partition named /dev/sda1
fsck.ext4 /dev/sda1	Check and repair a filesystem for any error
mount /dev/sda1 /mnt	Mount any partition to any directory
df -h	Display free space of mounted file system
df -i	Display free inodes on the filesystem
du -hs	Display the size of your current directory
lsblk	Display information about block devices
lsusb -tv	Display all USB devices
hdparm -tT /dev/sda	Perform a read speed test on disk /dev/sda
badblocks -s /dev/sda	Test for unreadable blocks on disk /dev/sda

Package Management Command

In this section, we will show a list of all commands to install, remove and manage packages in Linux.

Command	Description
apt-get install packagename	Install the package on Debian based distributions
apt-get remove packagename	Remove a package on Debian based distributions
dpkg -l | grep -i installed	Get a list of all packages on Debian based distributions
dpkg -i packagename.deb	Install .deb package
apt-get update	Update the repository on Debian based distributions
apt-get upgrade packagename	Upgrade a specific package on Debian based distributions
apt-get autoremove	Remove all unwanted packages on Debian based distributions
yum install packagename	Install the package on RPM-based distributions
yum remove packagename	Remove a package on RPM-based distributions
yum update	Update all system packages to the latest version on RPM-based distributions
yum list --installed	List all installed packages on RPM-based distributions
yum list --available	List all available packages on RPM-based distributions

Compress and Uncompress Commands

Tar, Zip, and Unzip are the most popular command-line utility in Linux used to compress and uncompress files and directories.

Command	Description
tar -cvf filename.tar filename	Compress a file in the Tar archive
tar -xvf filename.tar	Uncompress a Tar file
tar -tvf filename.tar	List the content of the Tar file
tar -xvf filename.tar file1.txt	Untar a single file from Tar file
tar -rvf filename.tar file2.txt	Add a file to the Tar file
zip filename.zip filename	Compress a single file to a zip
zip filename.zip file1.txt file2.txt file3.txt	Compress multiple files to a zip
zip -u filename.zip file4.txt	Add a file to a zip file
zip -d filename.zip file4.txt	Delete a file from a zip file
unzip -l filename.zip	Display the content of zip archive file
unzip filename.zip	Unzip a file
unzip filename.zip -d /dirname	Unzip a file to a specific directory

Conclusion

The above examples are the most commonly used Linux commands. I hope this will help you to perform your day-to-day system administration task.