Restrict SSH connections

[Philipp Marek]

> To limit amount of shells, you can use pam_limits [1], but it does not
> catch non-shell connections such as sftp, port forwarding, jumps to
> other servers and so on. For that, you need to use something home-
> cooked or some non-standard tool.

You could also use ulimit to restrict the total number of user
processes, if that works for your use-case.