Ubuntu. Login to text mode. It is not need to remove GUI from the system.
You can leave it and just make your default boot as a text mode and if once you need a GUI you can restore it so easy.
open /etc/default/grub as and add text to the
sudo nano /etc/default/grub
And in the file, change this line:
Then update your Grub
Your system will then always boot to text mode.
If you once want to use GUI you can easly make light works
sudo service lightdm start