[RFC] /etc/shells management (fish, mksh, posh, tcsh, zsh)

[Yaakov Selkowitz <yselkowitz at cygwin dot com>]

On 2016-05-11 14:06, Yaakov Selkowitz wrote:
> On 2016-05-11 12:09, Andrew Schulman wrote:
> > > Am 10.05.2016 um 20:19 schrieb Andrew Schulman:
> > > > Achim, can you please add /bin/fish and /usr/bin/fish to /etc/shells in
> > > > base-files?
> > >
> > > I seem to remember that this was discussed before.  If you could perhaps
> > > look up that discussion and fill me in what the conclusion was last time
> > > around?
> >
> > Hm, you're right, it was discussed before:
> >
> > https://www.cygwin.com/ml/cygwin/2014-02/msg00696.html
> >
> > I don't know if there was consensus, but the last word there from CGF was
> > that shell packages should run a postinstall step to add themselves to
> > /etc/shells.
>
> While I'm always ready to reconsider previous decisions, this is how it
> appears to be handled in Linux distros.  The implication thereof is that
> (once all packages have been adapted) the default /etc/shells should
> only contain those shells available by default (namely, sh, bash, and
> /sbin/nologin), e.g.:
>
> https://git.fedorahosted.org/cgit/setup.git/tree/shells
>
> (except that /sbin != /usr/sbin on Cygwin.)

AFAICS this should be a two-step process.

1) base-files' default /etc/shells should contain only the shells in a 
Base install, namely:

/bin/sh
/bin/ash
/bin/bash
/bin/dash
/usr/bin/sh
/usr/bin/ash
/usr/bin/bash
/usr/bin/dash
/sbin/nologin

2) Then all non-Base shells, namely:

fish                                         Andrew Schulman
mksh                                         Chris Sutcliffe
posh                                         Jari Aalto
tcsh                                         Corinna Vinschen
zsh                                          Peter A. Castro

will bump release adding an update_etc_shells call, per the attached 
patch, with the path of their shell(s).

> > That seems reasonable. There are questions about the right way to do it,
> > but I'll ask those in a separate thread.
>
> Probably best if we have a cygport function for creating the necessary
> postinstall and preremove commands.

Attached.  Any questions or comments before I make this official?

Or, is this just not worth the trouble?  What are the consequences of 
having shells listed in /etc/shells which aren't on the system?

--
Yaakov

Attachment: 0002-Add-update_etc_shells-for-etc-shells-management.patch
Description: Text document