restrict access to a system
rssh is a restricted shell for use with OpenSSH, allowing only scp and/or sftp. It now also includes support for rdist, rsync, and cvs. For example, if you have a server which you only want to allow users to copy files off of via scp, without providing shell access, you can use rssh to do that.
When a user has rssh as his/her shell, the user cannot login any more. His/her access is restricted to using one or more of scp, sftp, rsync, cvs, and rdist. This can be configured in /etc/rssh.conf.
The homepage of rssh is http://www.pizzashack.org/rssh/index.shtml