From the past version of Ubuntu the desktop environment change was made leaving the Unity project something that some users dislike, but it is not so bad, just reinstall it on the system to continue using it.
In this new entry I will share with you the way we can install Unity desktop environment on Ubuntu 18.04 and derived using the meta package that we find in the official Ubuntu repositories.
I should mention that the installation of this meta package apart from including all the necessary packages to run Unity the Lightdm login screen will also be installed, the complete Unity interface with global menu, default indicators, etc.
That is why some things will be replaced and you will be asked in the installation process, for example, if you want to replace gdm with Lightdm.
How to install Unity Desktop on Ubuntu 18.04 LTS and derivatives?
To install Unity on our system we just have to look for the meta package from the Ubuntu software center or we can support ourselves with Synaptic, just search for "Unity" and we must install the one that appears as "Unity Desktop"
Now if you prefer You can also do it from the terminal by executing the following command:
sudo apt install ubuntu-unity-desktop -y
With that will start downloading all necessary packages, during the configuration process we a screen will appear asking us which login manager they prefer.
If the Gnome (gdm) or Unity (Lightdm) one has already chosen the one of your preference and once the installation is finished, they must reboot their system.
Now only they must choose Unity on their login screen on the gear icon and they will be able to start their user session with this desktop environment.
Customizing the Unity installation
Being inside your user session you will be able to notice that the default gtk theme of Ubuntu 18.04 is still preserved, so we can resort to installing the Numix theme.
We can find the topic from the Ubuntu software center or if you prefer, you just have to open a terminal and run the following command to install it:
sudo apt install numix-gtk-theme
Now also to be able to customize our environment it is almost essential that we install the Unity retouching tool, for this we execute the following command on the terminal to install it on our system:
sudo apt install unity-tweak-tool
Once the installation is done with it, we will be able to change the gtk themes as well as the icons of our desktop environment to our liking.
How to uninstall Unity from Ubuntu 18.04 LTS and derivatives?
In case you want to remove the desktop environment from your system, I must remind you that before doing so you must have another environment installed on your systemIf you did not uninstall the Gnome environment, you can safely do this process.
I give you this warning because otherwise you will lose the only environment you have and you will have to work in terminal mode.
To uninstall the environment, you must close your Unity user session and log in to a different environment to this or you just have to open a TTY and run the following command:
sudo apt purge ubuntu-unity-desktop
Once this is done, if you chose the Unity login manager, you must reconfigure the previous one, in the case of Gnome you only have to execute the following command:
sudo dpkg-reconfigure gdm3
For Kubuntu, Xubuntu and others just replace gdm with their distribution.
Once this is done, we can remove lightdm from our system with the following command:
sudo apt purge lightdm
And that's it to finish we just execute this command To remove any packages that have been orphaned on the system:
sudo apt autoremove
Once this is done, it is necessary that we restart our computer for the changes to take effect and we can start our user session with another desktop environment.