I recently installed Ubuntu server on my server and I found out it had no GUI by default. So I installed it with the help of this page
Everything seemed to be fine so I started copying some files to my server. When I checked it to see if it was done I saw the lock screen that asked for the root password. But I never set that password so I tried the password which I set for my user account. I have also tried some other different passwords. I searched the internet and found out that there is no default password for root.
Am I stuck in this lock screen?
How should I shut the computer down? (there is no shutdown button in the lock screen)