Re: Switching /bin/sh to dash without dash essential

[Frans Pop <elendil@planet.nl>]

Manoj Srivastava wrote:
> I think we can engineer a system where Debian suggests various
> shells as the default shell, and the user selects one. And only the
> selected default shell is one that can't be removed from the system.

Debian Installer could in theory support this by having a default shell 
(varying per-architecture even). It could also prompt the user for which 
shell to use in expert mode.

The main challenge for installations would be that the default shell is 
installed by debootstrap, so that would need to be extended with a 
parameter to select a shell.

Problem is package priorities: can you have (pseudo) package that is 
priority required which is provided by packages that are all priority 
optional (which the shells would have to be to avoid them being installed 
automatically by debootstrap or the standard task)?
And that would also mean that no packages of prio standard or higher can 
be allowed to depend on a specific shell (as policy would make that shell 
package get the same priority).

In addition all shells supported as defaults would need to be included on 
CD images. And the selected shell would of course have to be set as the 
default for new users.
Debootstrap would still need a sane default in case no shell is set 
through a parameter or if the selected shell is not available for some 
reason.

For switching the default shell on an installed system, something (a prerm 
script shared between shell packages?) would need to check for the shell 
being removed whether there are users who have it as their default shell 
and what the default shell for new users is, and fail if the shell is 
still in use. I also feel that this is a case where showing a debconf 
dialog warning about possible consequences is appropriate.

Plenty of challenges...

Cheers,
FJP