There were a number of responses, but the basic answer is "no this
can't be done".
George Cameron offered a kludge solution of running a cron job to
update /etc/shells and Renny Koshy mentioned that wu-ftp has an
"anyshell" option to it. Since I don't know anyhting about wu-ftp,
nor what it would take to replace our existing ftpd's with it on
every machine, the kludge sounds like the way to go. Since the
shells are entered into the user's passwd entry in NIS, it makes
sense to leverage NIS for the job, so a shells map has been created.
The cron job will just ypcat -k the shells.byname map into
/etc/shells. I have no idea on the frequency requirements, but I
suspect it should be at least daily. It would be better if I could
just ask every machine to update its /etc/shells file at will, but
that's another post all together ;) (do_all.sh anyone?)
Thanks for all the responses.
Cheers,
Richard.