Today, I installed a Ubuntu server 16.04 LTS on my test lab. I installed it as a virtual machine on my Hyper-V host. When installation finished, I was presented with the server Core edition. As I am fairly new to Linux OS, I wanted to have Graphical User Interface (GUI). I went on Internet to find a way to convert my Core server to GUI. I learnt that I need to install ubuntu-desktop package to have GUI. sudo apt-get install ubuntu-desktop When I ran this command, I got a following error message: E: Unable to locate package update After doing a bit of a research, I found out that I will have to run some more commands to upgrade current package list before trying to install desktop version. I used following command to have GUI version of Ubuntu server. Use following command to upgrade packages installed on your PC or update your all system. When Prompted, type Y and press Enter key. Sudo apt-get upgrade Once you've upgraded your system, run this com