cons.saver man page
cons.saver — general-purpose Linux console screen save and restore server
Invoke this helper program with the Ctrl-o key combination to save and restore the user session on the screen.
cons.saver takes only one argument, the TTY NAME from which the system will save and restore.
Cons.saver does not need to be invoked by root. It only needs read and write access to /dev/vcsa*, which is a priviledged operation. You should create an unprivileged user, make cons.saver setuid to that user, and assure that all the vcsa* are owned by that user too.
Manpage written by Rodrigo Rubira Branco <email@example.com>