How to Kill X Server on Ubuntu 21.04 Guide

Killing X

1. First, Hit
   Ctrl+Alt+F1.

2. Then Login again
   So enter your Username & Pass.

3. And Kill the Display Manager.

   sudo service lightdm stop

   Or:

   sudo service gdm stop

   But if you have a Custom display manager then look for the command to Stop it…

4. Finally, Go to Runlevel 3
   With:

   sudo init 3

   To test you are on Ubuntu Server Mode issue:

   who -r