Ubuntu Server 20.04 LTS (or previous version) does not include a Graphical User Interface (GUI) upon installation. However, a desktop environment (a GUI) can be added after Ubuntu Server is installed. Installation is done from the command line interface (CLI) either with or without the necessity of installing or employing the task select manager utility (tasksel), which necessity will depend on the Display Manager and/or the GUI that you choose.

Since we want to have access to the latest packages that are available to install, it is good practice to begin with updating the repositories and package lists by entering the following at the CLI.

sudo apt-get update && sudo apt-get upgrade

Press y and the enter key at the prompt - 'Do you want to continue?“

If asked, enter your root/sudo password at the prompt.

This ensures that we have the most recent software updates.

Tasksel is a utility for simultaneously installing related software packages.

To install tasksel manager utility, enter the following at the CLI:

sudo apt-get install tasksel

If asked, enter your root/sudo password at the prompt.

The display manager chosen supports certain or various choices of the GUI / Desktop Environment that you select based on your choices of the look, feel, functionality of the display manager and GUI, as well as the resources that are consumed or preserved (with a heavier or more light weight display manager and/or GUI).

The “default” display manager is GDM3 which is relatively resource-intensive. The GDM3 display manager is used with and supports the KDE-Plasma Desktop GUI. In order to conserve resources, there are lighter display managers in the genus to choose from, such as SDDM, SLiM, and LightDM.

Here is how to install a specific display manager other than the GDM3 default display manager. It may involve the command line apt-get package manager to install, or by using the tasksel menu (addressed below).

The SDDM display manager can be installed from the tasksel menu during installation of KDE Desktop.

To install either SLiM or LightDM managers, use the apt-get Package manager as follows:

To install SLiM enter the following at the CLI:

sudo apt-get install slim

To install LightDM, instead enter:

sudo apt-get install lightdm

GNOME is the mostly the default desktop GUI.

KDE is a different popular GUI.

First, launch the tasksel manager from the CLI:

tasksel

A graphical installation interface will appear and you are prompted to choose which software to install from a long list. Use the down arrows to move the cursor down the list to Ubuntu desktop and press the space-bar to put a [*] next to “Ubuntu desktop.” Press Tab to select OK at the bottom of the interface list, and press Enter. The software will install and the operating system will reboot, resulting in a graphical login screen that will be generated from the display manager (default or chosen). For example, is we installed SLiM, then SLiM would generate the gnome ubuntu desktop login screen.

Enter you login credentials (password), to proceed to the graphical interface, in this case the GNOME UI environment.

To install KDE Plasma, use the following command:

sudo apt-get install kde-plasma-desktop

During installation, you may be asked to select a default display manager by using the arrow keys to make a selection and pressing the Enter key.

Next, launch KDE Plasma with one of the following commands, depending on the particular display_manager previously installed (namely, either SLiM, lightDM, SDDM):

sudo service Slim start

sudo service lightdm start

sudo service sddm start

If you are concerned about the substantial resource usage of these above Ubuntu Server GUI applications, then you may want to consider one of the lighter GUI applications, less resource-intensive GUI apps, listed below. This can conserve server resources.

Mate is a popular and lightweigtht GUI which can be installed as following:

sudo tasksel install ubuntu-mate-core

Mate can be launched after installation with one of the 3 following choices of your installed display manager:

sudo service slim start

sudo service lightdm start

sudo service sddm start

You will be prompted to enter your login credentials / password.

To exit the GUI, open the command line or console and enter one of the following commands, depending on you installed display manager – sudo service display_manager stop:

sudo service slim stop

sudo service lightdm stop

sudo service sddm stop

Use Lubuntu if you want to minimize the impact on your system memory and processors (GPU and/or CPU).

To install Lubuntu enter:

sudo tasksel install lubuntu-core

Or you can alternatively install Lubuntu from the tasksel graphical menu list by invoking tasksel as follows:

tasksel

Use the arrow keys and space bar to select the Lubuntu GUI, than Tab down to the OK button and press Enter to proceed with installing Lubuntu.

Launch The Lubuntu GUI with one of the applicable display manager that you have installed, as follows:

sudo service slim start

sudo service lightdm start

sudo service sddm start

Xubuntu uses the Xfce desktop environment.

Install Xubuntu with:

sudo tasksel install xubuntu-core

Launch Xubuntu with:

sudo service slim start

sudo service lightdm start

sudo service sddm start

Login.

Install Xfce with:

sudo apt-get install xfce4 slim

Launch Xfce with:

sudo service slim start

Login.

Xfce GUI is only compatible with the SLiM display manager.

If you have more than one GUI installed you can select which one GUI that you wish to use when you launch your display manager and are prompted to login. PRESS the F1 key at the login screen and you will be offered a selection from the multiple GUIs that are installed. Make your GUI choice and log-in with your credentials.