Logging out other users from the command line

this is one answer

who -u

that give you the PID

Then you can kill the user session.

kill "pid"

You may use who to check which users are logged in:

who

You can log-out the user by sending the KILL signal to the user-process with:

sudo pkill -KILL -u <username>

(which is same as sudo pkill -9 -u <username>)

example:

sudo pkill -9 -u guest-2Rw4Lq

(to kill a guest session user named guest-2Rw4Lq)

Note (kudos to pbhj): If you get locked in a console, use Ctrl+Alt+F7 to get back to the GUI.

who -u


> adam     ttys000  Aug  4 09:22   .       91228 

then

sudo kill 'PID number'
sudo kill 91228

PID (process ID) is the four or five digit number at the end of the user readout (91228)