Re: Public PC freeze configuration
If you set the machines up for automatic guest login per grahammechanical's second link, there are still ways to accomplish administrative tasks.
You could install openssh-server on the machines so that you can ssh into them. A lot of administrative tasks can be handled through the CLI and can be managed that way.
Then, you could create two different versions of /etc/lightdm/lightdm.conf (one with automatic guest login and one without) which you store somewhere else. Then, you could create two shell scripts that copy one or the other to /etc/lightdm/lightdm.conf. That way, for non-CLI admin tasks, you could ssh in and run the shell script disabling automatic guest login.
Jane, stop this crazy thing!