How do I restart Cinnamon from the tty?
Hit Alt+F2, type r and hit enter.
The cinnamon --replace process can be sent the HUP signal which will trigger it to restart, thus preserving your open window and running applications.
$ pkill -HUP -f "cinnamon --replace"
This will take care to send the HUP signal to a process that matches the pattern, "cinnamon --replace". The signal HUP (SIGHUP) tells the process to "Hang Up".