I lost Ubuntu Graphical Interface (GUI) about year ago. This problem was caused by a currupted Ubutu softare package. If your Ubuntu desktop OS does not start desktop interface and if you think your Ubuntu software pacakge is damaged, you should clean package. This what I did and got my Ubuntu desktop interface back.

At first, you should make sure that your Ubuntu can access to interne because you need to download the pckages. When you lose Ubuntu desktop, you also lose your internet access at the same time. My Ubuntu lost the internet access beucase of the software package curruption. Here is what I did to get my internet back.

To manually setup IP Address: 

sudo ip address add <available IP Address>/24 dev enp5s0 
sudo ip link set <network interface name (e.g., enp0s25)> up 
sudo ip route add default via <default gateway IP Address>

Set DNS: 

echo "nameserver 8.8.8.8" | sudo tee /etc/resolv.conf > /dev/null

Initialize sources.list

Initialize sources.list.  

Rename source.list: mv /etc/apt/sources.list /etc/apt/sources.list.old 

mv /etc/apt/sources.list /etc/apt/sources.list.old

Copy barebone source.list from /usr/share/doc/apt/examples/sources.list

sudo cp /usr/share/doc/apt/examples/sources.list /etc/apt/sources.list

Update and install python3 because Ubuntu software pacakge depends on python scripts. 

sudo apt-get update 
sudo dpkg --configure –a 
sudo apt-get -f install 
sudo apt-get install build-essential  
sudo apt autoremove 
sudo apt install python3

Reboot.

    If you still do not see Ubuntu desktop interface, you may need to install UBuntu Desktop Application again.

    Install tasksel. 

    sudo apt-get install tasksel

    List GUI applications.

    tasksel --list-tasks 

    Install Ubuntu Desktop.

    sudo apt-get install ubuntu-desktop

    After all these operation, I got my Ubuntu desktop GUI came back on. I hope this post help some of you.

    By : Peita