Linux distributions can start and stop the graphical desktop in various ways. The exact method differs from distribution and among distribution versions. For the newer systemd-based distributions, the display manager is run as a service, you can stop the GUI desktop with the systemctl utility and most distributions will also work with the telinit command, as in:
$ sudo systemctl stop gdm (or sudo telinit 3)
and restart it (after logging into the console) with:
$ sudo systemctl start gdm (or sudo telinit 5)
On Ubuntu versions before 18.04 LTS, substitute lightdm for gdm.
