Important Linux commands

All the tools you need as a server admin

It is difficult to compile a definitive list of the most important commands on Linux, as the importance of different commands can vary depending on the specific needs and tasks of the user.

Let's try it anyway! Here is our all-time favorite list of commonly used and important commands on Linux systems, that you should definitely know:

bash: widely used Unix shell
cat: concatenate and display files
cd: change the current directory
cp: copy files and directories
df: display information about free disk space
du: display the size of a file or directory
echo: display a message or the value of a variable
kill: send a signal to a process
less: view the contents of a file one page at a time
ls: list the contents of a directory
man: display the manual page for a command
mc: start the Midnight Commander
mkdir: create a new directory
mv: move or rename files and directories
ping: send a network test packet
ps: display information about running processes
pwd: print the current working directory
rm: delete files and directories
rsync: synchronize files between two systems
screen: run multiple "tabs" in one terminal session
ssh: connect to a remote host using the Secure Shell (SSH) protocol
sudo: execute a command as root
tail: display the last few lines of a file
top: display the top running processes

Here at CleverUptime, we are using all of those commands on a daily basis. They make our life easier and everybody knows them by heart.

If you read this far, you probably know already all the commands above and you're interested to learn about other commands that can help you as an admin.

Great! Here is the extended list:

ab: a tool for benchmarking web servers
alias: create a shortcut for a command
apt: install, remove, and manage software packages
apt-cache: search for and display information about software packages
apt-get: install, remove, and manage software packages
aptitude: a high-level interface for managing packages in Debian-based systems
aria2c: download files using different protocols
at: execute a command at a specified time
atop: show performance metrics
awk: perform text processing and data manipulation tasks
bg: resume a suspended job in the background
blkid: identify and manage filesystem labels and UUIDs
btrfs: manage the btrfs file system
bunzip2: decompress .bz2 files
bzip2: compress files using the Burrows-Wheeler block-sorting compression algorithm
cancel: remove jobs from the print queue
certbot: manage SSL/TLS certificates from Let's Encrypt
chgrp: change the group ownership of a file or directory
chkconfig: manage system services across runlevels
chmod: change the permissions of a file or directory
chown: change the owner of a file or directory
comm: compare two sorted files line by line
crontab: schedule a command to be executed at a specified time
cryptsetup: encrypt block devices
csh: launch the C shell, a Unix command interpreter with C-like syntax
curl: transfer data to or from a server
cut: extract fields or columns from a file
date: display the current date and time
dd: copy data between block devices
dd_rescue: rescue data from block devices
dhclient: request and configure network parameters using DHCP
diff: compare two files and display the differences
dig: query the domain name system
dispatch-conf: update configuration files with Gentoo Linux
dmesg: view the kernel's message buffer
dnf: install, remove, and manage software packages on Fedora-based systems
docker: manage software running in containers
dosfsck: check and repair FAT file systems
dpkg: install, remove, and manage Debian package files
dpkg-reconfigure: reconfigure installed packages in Debian-based systems
e2fsck: check and repair ext file systems
ebuild: manage and install Gentoo packages manually
emacs: edit text files with the Emacs editor
emerge: install, remove, and manage software packages on Gentoo-based systems
equery: query information about installed packages in Gentoo
eselect: manage system configurations in Gentoo
etc-update: merge updated configuration files in Gentoo
exec: replace the current shell process with a specified command
export: set the value of an environment variable
exportfs: export directories to NFS clients
fdisk: manage partitions on hard drives and SSDs
fdupes: find and manage duplicate files
ffmpeg: manipulate multimedia files
fg: bring a background job to the foreground
file: determine the type of a file
find: search for files and directories
flock: manage file locking from shell scripts
fold: adjust the width of output
free: display information about free and used memory
fsck: check and repair a file system
fuser: identify processes using files or sockets
gcc: compile C files
gdb: debug programs written in various languages
gdisk: guided partition table manipulation
genkernel: automate kernel and initramfs generation in Gentoo
getenforce: display SELinux status (enforcing, permissive, or disabled)
getent: get information from administrative databases
git: a version control system
gpasswd: administer /etc/group and manage group passwords
grep: search for a pattern of text within a file
groupadd: add a group
groupdel: delete a group
groupmod: modify a group
gunzip: decompress files
gzip: compress or decompress files
halt: shut down the system
head: display the first few lines of a file
hexdump: display file contents in hexadecimal, decimal, octal, or ASCII
host: query DNS servers
hostname: display the hostname of the system
htop: display performance metrics
id: display user and group IDs
ifconfig: display information about network interfaces
init: change the runlevel
iostat: display information about the current I/O performance
iotop: display performance metrics for I/O
ip: display and configure network interfaces
iptables: configure the kernel's firewall
jobs: display active jobs in the current shell session
join: join lines of two files on a common field
journalctl: display logging information
jq: process JSON input and produce JSON output
killall: terminate processes by name
ksh: launch the Korn shell, a Unix command interpreter
last: display users who logged in last
lastb: show failed login attempts
lastlog: display the last login time for each user
ldconfig: configure dynamic linker run-time bindings
lilo: install and configure the Linux bootloader
ln: manage hard and soft links
locate: search for files and directories using a database
logger: add messages to the system log
logrotate: organize log files
lp: send files to the printer
lpq: check the print queue
lpr: send files to the printer
lprm: remove jobs from the print queue
lpstat: display information about print jobs
lsb_release: display information about your Linux distribution
lsblk: list block devices
lsmod: list loaded kernel modules
lsof: list open files
lspci: list PCI devices
lvcreate: create logical volumes
lvdisplay: show logical volumes
lvremove: delete logical volumes
lynx: browse the Web in a terminal window
mailq: manage the mail queue
md5sum: calculate the MD5 checksum
mdadm: manage RAID devices
memtest86: test the RAM
mkfs.btrfs: format a device with btrfs
mkfs.ext4: format a device with ext4
mkfs.ntfs: format a device with NTFS
mkfs.vfat: format a device with FAT
mkfs.xfs: format a device with XFS
mkswap: create swap space
modprobe: add or remove kernel modules
more: view the contents of a file one page at a time
mount: make file systems accessible in the directory tree
mutt: manage emails
mysqldump: create backups of your MySQL database
nano: edit text files with the Nano editor
nc: send data over the network
netconfig: configure network interfaces
netstat: display network statistics
nft: configure the kernel's firewall
nice: run a command with a modified scheduling priority
nmap: scan for open ports and services
nohup: run a command immune to hangups, with output to a non-tty.
nslookup: query DNS servers
ntpq: query NTP servers
openssl: manage SSL certificates
pacman: install, remove, and manage software packages on Arch Linux-based systems
partprobe: re-read the partition table
passwd: set user passwords
paste: combine lines of files
patch: apply a diff file to an original file
pdftk: manipulate PDF files
pkgtool: the Slackware package manager
pmap: report memory usage of a process
printenv: display the value of an environment variable
ptrace: trace and control system calls of a running process
pv: monitor the progress of a pipe
pvcreate: create a physical volume
pwd: print the current working directory
python: run Python scripts
qemu-img: manage virtual machine images
rclone: the swiss army knife for cloud storage
readlink: display information about hard and soft links
reboot: restart the system
renice: alter the priority of a running process
rmdir: delete an empty directory
rmmod: remove Kernel modules
route: modify the IP routing table
rsnapshot: create file system backups
run-parts: execute scripts or programs in a directory
sar: monitor performance metrics
scp: copy files to or from a remote host using the Secure Copy (SCP) protocol
sed: perform text manipulation and substitution tasks
semanage: manage SELinux policy settings
sendmail: send emails
sestatus: display current SELinux status and policy
setenforce: switch between enforcing and permissive mode in SELinux
setsebool: enable or disable SELinux boolean values
sftp: transfer files to or from a remote host using the Secure File Transfer Protocol (SFTP)
sh: launch the Bourne shell
sha1sum: compute and verify SHA-1 hash values
sha256sum: compute and verify SHA-256 hash values
showmount: display NFS server information
shutdown: turn off or reboot the system
sleep: do nothing for a specified time
smartctl: show health and performance data of disk drives
snmpwalk: a tool for network management
sort: sort the lines of a file
ss: show information about network connections
ssh-add: add private key identities to the SSH authentication agent
ssh-agent: manage private keys for secure shell connections
ssh-copy-id - add SSH keys to a remote server
ssh-keygen: generate keys for SSH
strace: trace system calls and signals
stress: load and stress test your system
strings: extract printable strings from files
su: become the superuser
swapoff: deactivate swap space
swapon: activate swap space
sysctl: a tool for fine-tuning your system
systemctl: manage services
tac: display files in reversed order
tar: create and extract archive files
tcpdump: capture network packages
tee: chaining together standard input and output
telnet: connect to a remote host using the Telnet protocol
timeout: run a command with a time limit
tmux: run multiple "tabs" in one terminal session
touch: create a new file or update the modification time of an existing file
tr: modify standard output
traceroute: display the network path to a host
visudo: edit the sudoers file safely
trap: handle signals and events in shell scripts
tune2fs: adjust tunable file system parameters on ext2/ext3/ext4
ufw: uncomplicated firewall for managing iptables rules
ulimit: set or display user-level resource limits
umount: remove file systems from the directory tree
uname: display information about the system
uniq: remove duplicate lines from a file
unset: unset the value of an environment variable
unzip: unpack files from a ZIP archive
unzstd: unpack files using ZStandard
update-alternatives: configure default programs for your system
uptime: display the current uptime of the system
useradd: add users
userdel: delete users
usermod: modify users
vi: edit text files with the vi editor
vim: edit text files with the Vim editor, a highly configurable text editor.
virsh: manage and interact with virtual machines through the command line.
virt-install: create virtual machines
virt-manager: manage virtual machines
visudo: safely edit the sudoers file, which defines user privileges.
vmstat: display performance statistics
watch: run a program in regular intervals
wc: count the number of lines, words, and characters in a file
wget: download files from the Web
whereis: display the location of a command, file, or manual page
which: display the path of a command
who: display a list of users which are currently logged in
xargs: transform text into commands
xfs_repair: repair XFS file systems
xz: compress or decompress files
yast: configure a SUSE based system
yum: install, remove, and manage software packages on Red Hat-based systems
zip: compress files into a ZIP archive
zsh: launch the Z shell, an extended version of the Bourne shell with many features
zstd: compress or decompress files
zypper: install, remove, and manage software packages on openSUSE-based systems

This is just a small selection of the many commands that are available on Linux systems. There are many other important and useful commands that may be specific to certain applications, programming languages, or tasks, and it is always a good idea to familiarize yourself with the commands that are relevant to your work.