In reply to フェリックスたん.

I was pointed to dbus settings for 'gdm' and this should do the trick. "sudo -u gdm dbus-run-session gsettings list-recursively org.gnome.settings-daemon.plugins.power | grep sleep" list all options and removing the timeout should prevent this: "sudo -u gdm dbus-run-session gsettings set org.gnome.settings-daemon.plugins.power sleep-inactive-ac-timeout 0"

I'll update the article once confirmed.