Essential Linux commands for beginners

The command line is intimidating at first, but about thirty commands cover 90% of everyday needs: moving around, managing files, installing software, monitoring the machine. This guide groups them by task, each with an example you can type as is.

The examples are given for Debian and Ubuntu. Almost everything works the same on other distributions; only software installation differs (see part 7).

1. Terminal basics

Open a terminal: on Ubuntu, Ctrl + Alt + T, or search for "Terminal" in your applications. You see a line like this one, called the prompt:

spo@laptop:~$

It shows the user (spo), the machine name (laptop) and the folder you are in (~ means your home folder). The $ marks a regular user; a # marks the administrator account, root.

A command is always built the same way:

command -options arguments
ls -l /home

Here, ls is the command (list), -l the option (detailed view) and /home the argument (the folder to list). Linux is case-sensitive: Documents and documents are two different folders.

2. Finding your way around

Two ways to write a path:

• Absolute, from the root of the system, starts with /: /home/spo/Documents.
• Relative, from the current folder: Documents/invoices.

Files whose name starts with a dot (.bashrc, .ssh) are hidden: only ls -a shows them.

3. Managing files and folders

The * character stands for "anything": *.jpg means every file ending in .jpg. If a name contains spaces, put it in quotes: cd "My documents".

4. Reading a file

5. Editing a file with nano

nano is the simplest text editor, installed almost everywhere:

nano notes.txt

You type the text directly. The shortcuts are listed at the bottom of the screen (^ means Ctrl):

• Ctrl + O then Enter: save;
• Ctrl + X: quit;
• Ctrl + W: search;
• Ctrl + K: cut the line, Ctrl + U: paste it.

For a system file, add sudo in front: sudo nano /etc/hosts. Make a copy before editing a configuration file: sudo cp /etc/hosts /etc/hosts.bak.

6. Finding a file or some text

7. Installing and updating software

Each family of distributions has its own package manager. It downloads software from the official repositories, checked by the distribution: that is the method to prefer over downloading files from websites.

On Debian and Ubuntu, apt update refreshes the list of available software and apt upgrade installs the updates: always run both, in that order. sudo apt autoremove then removes packages that are no longer needed.

8. Users and permissions

sudo runs a command with administrator rights. It asks for your password (not root's), and nothing is displayed while you type: that is normal.

In an ls -l listing, the first column shows the permissions, for example -rwxr-xr--. After the first character (- for a file, d for a folder), you read three groups of three letters: the permissions of the owner, the group, then everyone else. r = read, w = write, x = execute (or enter, for a folder).

They are often written as numbers: r = 4, w = 2, x = 1, added together. The two values to know:

• chmod 644 file: you read and write, others only read (ordinary files);
• chmod 755 folder: you do everything, others read and enter (folders, scripts).

9. Monitoring the system

If kill is not enough, kill -9 4321 forces the process to stop, without giving it time to save: keep it as a last resort.

10. Managing services

Services (web server, SSH, printing…) run in the background. On almost every current distribution, they are controlled with systemctl:

systemctl status ssh          # service status
sudo systemctl restart ssh    # restart
sudo systemctl stop ssh       # stop
sudo systemctl start ssh      # start
sudo systemctl enable ssh     # start automatically at boot
journalctl -u ssh -n 50       # its last 50 messages

The service name varies by distribution: ssh on Debian and Ubuntu, sshd on Fedora or Rocky. Pressing Tab after systemctl status suggests the available names.

To shut down or restart the machine: sudo poweroff and sudo reboot.

11. Networking in a few commands

To go further: network troubleshooting and securing SSH access.

12. Archiving and compressing

tar -czf backup.tar.gz Documents/     # create a compressed archive
tar -tzf backup.tar.gz                # list its contents
tar -xzf backup.tar.gz                # extract it into the current folder
unzip archive.zip                     # extract a .zip

To remember tar: c = create, x = extract, t = list, z = gzip compression, f = file name (always last). unzip is not always installed: sudo apt install unzip.

13. Combining commands

The real power of the terminal is chaining commands:

And to find what you already typed:

• history: lists the latest commands;
• Ctrl + R then a few letters: searches the history;
• clear or Ctrl + L: clears the screen.

14. Getting help

• man ls: the full manual of a command (q to quit, /word to search);
• ls --help: a summary of the options, quicker to read;
• tldr ls: concrete examples rather than a manual, installed with sudo apt install tldr on Ubuntu (elsewhere, apt search tldr gives the package name).

Key takeaways

• Tab to complete, ↑ to recall, Ctrl + C to stop.
• pwd, ls, cd to find your way; cp, mv, rm, mkdir for files.
• rm does not use the bin: check with ls first.
• Regular updates: sudo apt update && sudo apt upgrade (or your distribution's equivalent).
• sudo only when needed, and never a command copied from the internet without understanding it.