How do I start GUI mode in Ubuntu?

sudo systemctl enable lightdm (if you enable it, you’ll still have to boot in “graphical. target” mode to have GUI) sudo systemctl set-default graphical. target Then sudo reboot to restart your machine, and you should be back to your GUI.

How do I get to GUI in terminal?

Ubuntu 18.04 allows me to go to terminal mode with Ctrl+Alt+F3 and back to GUI with Ctrl+Alt+F1.