The command line might seem like a scary place. With no fancy GUI windows to click on just you, your keyboard, and a (in most cases) bash prompt.

Understanding the terminal

A terminal or terminal emulator is a program that emulates a video terminal in some sort of other video environment, like a GUI. These terminal emulators provide an environment for application like a text shell or CLI application to run in. The most common shell on linux is the BASH, or born again shell, shell. A typical bash prompt could look like the following:

nathan@virtmachine:~$

This prompt is split up into the following parts

• The first part is the current username, in this case it is nathan
• The second part is the hostname of the PC or the PC’s name, in this case it is virtmachine
• The Third part is the path, in this case it is ~
• The fourth path tells you if you are a regular user of root, in this case it is a normal user indicated by the $

You can change this prompt to give you different information, with specific programs designed to change the shell prompt like starship, which is what I use. This shell provides a scripting language as well a way to invoke programs.

Opening a terminal windows

To get started using the CLI, you need to open you terminal emulator, on a generic ubuntu install, click on the nine dots in the bottom right: the search of ‘Terminal’. The click on the ‘Terminal’ application. This should open up the following window .

If this is the first time opening the terminal, you might see a message about the sudo command. This command is the equivalent of ‘Run as administrator’.

Navigating the file system

An important thing to know how to do in the terminal is how you navigate the file system. Firstly you may want to know where you are in the file system, to do this use the pwd command:

pwd

This will show you your current path. To change directory you can use the cd command.

cd <path>

This allows for you to change into any given directory. with the given path. For example if you want to enter you downloads folder use:

cd ~/Downloads

Note: the ~ is being used in place for /home/nathan, my home directory.

If you need to go up a directory, i.e. from /home/nathan/Downloads to /home/nathan, you can use

cd ..

Finally, you can list the contents with the ls command.

ls

This will show everything in the director, although not the directory any hidden files, if you want to show hidden files use the -a flag

ls -a

Running as administrator

To run software as administrator like a package manager or systemctl because they need elevated access to preform the actions. This can be done using the sudo command.

sudo <command>

This command is very useful for all sorts of different uses.

Managing services

Majority of the linux system will use the systemd init system to start and manage services on linux. Services are just programs that have a specific task running in the background, like Wi-Fi and sound. Services can be started and stopped and queried using the systemctl command.

Starting a service

To start a service, use

sudo systemctl start <service>

This will start service in the background

Querying the status of a service

A service can be queried with

sudo systemctl status <service>

Stopping a service

A service can be stoped with

sudo systemctl stop <service>

Starting a service at boot

A service can be started on boot using the

sudo systemctl enable <service>

This will start the service in the background

Stopping a service

A service can be stopped using

sudo systemctl disable <service>