I recently installed Ubuntu 18.04 (previously 16.04) and an important feature is missing: the option to switch between GUI and TTY. From the GUI I can switch to one of 5 TTY, by Ctrl-Alt-F2 to Ctrl-Alt-F6. I can login in the tty, do whatever I wish. When I Press Alt-F1, I get to the login-screen, not back to running GUI session. More @Wikipedia
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