On a PC for public use people enter very private data, then don't logout, which doesn't seem optimal, so I would like if anyone could tell me how to automatically log out the guest session user after idle time. The OS is Linux Mint 18.3 64-bit Cinnamon. All the ways of automatically logging somebody out I have found, don't seem to work for the guest session.
"Log out idle users
The program reads the utmp file, entry by entry. The username for each 'user process' is compared to the entries in the configuration file. The first entry to match both the name, the group, and the tty line of the process will be used to conduct the automatic logout."