restricted shell w/ bash?

I'm trying to setup certain users with a restricted shell. I've seen mention of invoking bash with a -r or "rbash", but I'm unsure how to do this via Netinfo. One tip suggested creating a symlink to bash that's named rbash, but that doesn't appear to work. Ideally I'd like to set this restricted shell when the account is created - I'm using a shell script that has a line like the following...

echo 'shortname::520:520::0:0:longname:/Users/shortname:/bin/bash' | sudo niload -v passwd /

All this is for a machine that will be configured soley as a ssh box for users to connect to and download data via scp, with no further privleges.