Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site bu-cs.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!harvard!bu-cs!root From: root@bu-cs.UUCP (Barry Shein) Newsgroups: net.unix Subject: Re: Alternate Shells Message-ID: <575@bu-cs.UUCP> Date: Tue, 13-Aug-85 22:34:02 EDT Article-I.D.: bu-cs.575 Posted: Tue Aug 13 22:34:02 1985 Date-Received: Thu, 15-Aug-85 21:55:46 EDT References: <10672@Glacier.ARPA> Organization: Boston Univ Comp. Sci. Lines: 33 >From: conor@Glacier.ARPA (Conor Rafferty) >Subject: Alternate Shells >Summary: Why is chsh fascist? >A quickie: 4.2BSD chsh does not allow the user to specify alternative >shells - only "sh" and "csh" are permitted. Why is this? It seems >ironically inappropriate in UNIX, where the shell is ``an ordinary, >swappable user program'' and ``user-selectable system interfaces [...] >become essentially trivial to implement'' [Ritchie & Thompson CACM 1974]. One obvious reason probably had more to do with the 'nuisance' of people setting various things to be their shell and then finding out it was a bad choice and rendering their account useless thus going and bothering some SA to unjam them. Note that chsh was a Berkeley thing and kids will be kids...(it's easy, by the way, to either change or re-write chsh to be more liberal or accept a wider variety of things, but obviously a priv'd account would have to install it.) Note that if you are priv'd I believe chsh lets you set to anything (besides, at that point you don't need chsh.) Another reason that nags the back of my mind is a security hole, but by the time a shell is exec'd for you in login you are already setuid()'d and setgid()'d to you so it doesn't seem to me it opens any hole that isn't already there...hmmm. I think you can see it more as a site policy rather than a restriction imposed by UNIX. Go bug your SA if you have a good argument. Alternatively, you could easily accomplish the same effect through your .login file, just put the command you want right there, no? -Barry Shein, Boston University