I'm going to be deploying an Linux machine as a sort of public terminal at a remote location. I'd like to be able to access it remotely via SSH for maintenance but I don't want to keep a port open on the remote firewall for the rare occasions I need to access this machine. I've though about a simple script to create a reverse SSH tunnel to a machine on the outside, but I'd rather not have to have a user have to do anything when I need to access it. Any ideas?
Update: I've decided to go with my original plan of a script to create a reverse ssh tunnel. While other suggested solutions, such as port knocking would be more along the lines of what I really want to do, in this case, I don't have any access to configure the router other than walking a user through a config. shudder