Essential Ubuntu Commands: A Practical CLI Cheat Sheet

If you manage an Ubuntu server, these are some of the most useful commands to know. This cheat sheet covers system updates, files, directories, disk space, services, networking, logs, permissions, processes, and other everyday server administration tasks.

Most examples work on modern Ubuntu releases, including Ubuntu 24.04 LTS.

System Updates

Update the package list

Checks configured repositories for the latest available packages. This does not install updates.

sudo apt update

See available updates

apt list --upgradable

Install available updates

sudo apt upgrade

Perform a full upgrade

Allows APT to install or remove packages when necessary to complete an upgrade.

sudo apt full-upgrade

Always review the packages APT proposes to remove before approving a full upgrade on a production server.

Remove packages that are no longer needed

sudo apt autoremove

Clean the package cache

sudo apt autoclean

Install a package

sudo apt install package-name

Example:

sudo apt install htop

Remove a package

sudo apt remove package-name

Completely remove a package and its configuration

sudo apt purge package-name

System Information

Check the Ubuntu version

lsb_release -a

Or:

cat /etc/os-release

Check the kernel version

uname -r

Show detailed system information

hostnamectl

Check how long the server has been running

uptime

Check the current hostname

hostname

Check the current date and time

date

Check timezone configuration

timedatectl

CPU and Memory

Check memory usage

free -h

View running processes and resource usage

top

Use a more user-friendly process monitor

htop

If it is not installed:

sudo apt install htop

Check CPU information

lscpu

Check the number of CPU cores

nproc

Disk Space

Check disk usage

df -h

Check the size of the current directory

du -sh .

Check the size of a specific directory

du -sh /var/log

Show the size of files and directories in the current location

du -sh *

Sort directories by size

du -sh * | sort -h

View disks and partitions

lsblk

Interactive disk-space analyzer

ncdu

Install it with:

sudo apt install ncdu

Then, for example:

sudo ncdu /

Navigating the Filesystem

Show your current location

pwd

List files

ls

Detailed file listing

ls -lh

Show hidden files

ls -la

Detailed listing with human-readable file sizes

ls -lah

Change directory

cd /path/to/directory

Go up one directory

cd ..

Go to your home directory

cd ~

Go to the previous directory

cd -

Creating, Copying, Moving, and Deleting Files

Create a directory

mkdir new-directory

Create nested directories

mkdir -p path/to/new/directory

Create an empty file

touch file.txt

Copy a file

cp file.txt copy.txt

Copy a directory

cp -r source-directory destination-directory

Move a file

mv file.txt /new/location/

Rename a file

mv old-name.txt new-name.txt

Delete a file

rm file.txt

Delete an empty directory

rmdir directory-name

Delete a directory and everything inside it

rm -rf directory-name

Be extremely careful with rm -rf. Deleted files do not go to a recycle bin.

Viewing and Editing Files

Display an entire file

cat file.txt

Scroll through a large file

less file.txt

Press q to exit.

Show the first 10 lines

head file.txt

Show the last 10 lines

tail file.txt

Show the last 100 lines

tail -n 100 file.txt

Watch a file for new lines in real time

Excellent for monitoring log files:

tail -f /var/log/nginx/error.log

Press Ctrl+C to stop watching.

Edit a file with Nano

nano file.txt

In Nano:

• Ctrl+O saves the file
• Ctrl+X exits
• Ctrl+W searches
• Ctrl+K cuts a line
• Ctrl+U pastes a line

Searching for Files

Find a file by name

find /path -name "filename.txt"

Search the entire server:

find / -name "filename.txt" 2>/dev/null

Case-insensitive search

find / -iname "filename.txt" 2>/dev/null

Find directories

find / -type d -name "directory-name" 2>/dev/null

Searching Inside Files

Search a file for text

grep "search text" file.txt

Case-insensitive search

grep -i "error" file.txt

Search recursively through a directory

grep -R "search text" /path/to/directory

Include line numbers

grep -n "search text" file.txt

Search logs for errors

grep -i "error" /var/log/nginx/error.log

Users and Permissions

Show the current user

whoami

Show user and group information

id

Show groups

groups

Change a user’s password

passwd username

Change file ownership

chown user:group file.txt

Recursively change ownership:

chown -R user:group directory/

Set standard file permissions

chmod 644 file.txt

Set standard directory permissions

chmod 755 directory/

Make a script executable

chmod +x script.sh

Run a command as another user

sudo -u username command

Managing Services with systemd

Check a service

systemctl status nginx

Start a service

sudo systemctl start nginx

Stop a service

sudo systemctl stop nginx

Restart a service

sudo systemctl restart nginx

Reload a service without a full restart

sudo systemctl reload nginx

Check whether a service is running

systemctl is-active nginx

Enable a service at startup

sudo systemctl enable nginx

Disable a service at startup

sudo systemctl disable nginx

Show failed services

systemctl --failed

Logs and Troubleshooting

View recent system logs

journalctl

Show recent errors

journalctl -xe

View logs for a specific service

journalctl -u nginx

Show the last 100 log entries for a service

journalctl -u nginx -n 100

Watch service logs live

journalctl -u nginx -f

Show logs from the current boot

journalctl -b

Show kernel messages

dmesg

Process Management

Show running processes

ps aux

Find a particular process

ps aux | grep nginx

Find a process ID

pgrep nginx

Stop a process

kill PID

Example:

kill 12345

Forcefully terminate a process

kill -9 PID

Use kill -9 only when a normal termination does not work.

Networking

Show network interfaces and IP addresses

ip addr

Short version:

ip a

Show routing information

ip route

Test connectivity

ping google.com

Check your server’s public IP

curl ifconfig.me

Check HTTP response headers

curl -I https://example.com

Follow redirects

curl -IL https://example.com

Download a file

wget https://example.com/file.zip

Or:

curl -O https://example.com/file.zip

DNS Troubleshooting

Look up a domain

dig example.com

Look up a specific DNS record

dig example.com A

dig example.com MX

dig example.com TXT

dig www.example.com CNAME

Get a short DNS answer

dig +short example.com

Query a specific DNS resolver

dig @1.1.1.1 example.com

Trace DNS delegation

dig +trace example.com

Ports and Connections

Show listening ports and the processes using them

ss -tulpn

Check whether port 443 is listening

ss -tulpn | grep :443

Check whether port 80 is listening

ss -tulpn | grep :80

SSH

Connect to a server

ssh username@server-ip

Connect using a hostname

ssh username@example.com

Generate an SSH key

ssh-keygen

Copy your SSH public key to a server

ssh-copy-id username@server

Copy a local file to a remote server

scp file.txt username@server:/path/

Copy a remote file to your computer

scp username@server:/path/file.txt .

Archives and Compression

Create a ZIP archive

zip -r archive.zip directory/

Extract a ZIP archive

unzip archive.zip

Create a compressed TAR archive

tar -czf backup.tar.gz directory/

Extract a TAR.GZ archive

tar -xzf backup.tar.gz

View the contents without extracting

tar -tzf backup.tar.gz

Command History

Show command history

history

Search your history

history | grep nginx

Repeat the previous command

!!

An even better trick is pressing:

Ctrl+R

Then start typing part of an old command to search your command history interactively.

Cron Jobs

View your cron jobs

crontab -l

Edit your cron jobs

crontab -e

Check the cron service

systemctl status cron

Rebooting and Shutting Down

Reboot the server

sudo reboot

Shut down immediately

sudo shutdown -h now

Schedule a reboot in 10 minutes

sudo shutdown -r +10

Cancel a scheduled shutdown or reboot

sudo shutdown -c

Useful Keyboard Shortcuts

Shortcut	Action
Tab	Auto-complete commands and paths
Ctrl+C	Stop the current command
Ctrl+L	Clear the terminal
Ctrl+R	Search command history
Ctrl+A	Move to beginning of line
Ctrl+E	Move to end of line
Ctrl+U	Delete from cursor to beginning
Ctrl+K	Delete from cursor to end
↑ / ↓	Browse previous commands

A Simple Ubuntu Server Update Routine

For routine server maintenance, start by refreshing the package information:

sudo apt update

See exactly what can be upgraded:

apt list --upgradable

Install the available updates:

sudo apt upgrade

Check whether Ubuntu requires a reboot:

test -f /var/run/reboot-required && echo "Reboot required" || echo "No reboot required"

Check for failed services:

systemctl --failed

Check disk space:

df -h

Check memory:

free -h

If a reboot is required:

sudo reboot

The Commands Worth Memorizing

If you only memorize a handful of Ubuntu commands, make them these:

pwd
ls -lah
cd
cp
mv
rm
nano
cat
less
tail -f
grep
find
df -h
du -sh
free -h
top
htop
ps aux
systemctl status
systemctl restart
systemctl --failed
journalctl -xe
ip a
ss -tulpn
curl -I
dig
apt update
apt list --upgradable
apt upgrade
history
reboot

These commands cover a surprisingly large percentage of everyday Ubuntu server administration.