Gerrit Pape wrote:
> You know, I know how to do it.
Okay, I did some digging in the archives. Sorry to those who
already went over this all.
debian-package-dash-getv...@list.smarden.org
debian-package-dash-getv...@list.smarden.org
debian-package-dash-getv...@list.smarden.org
In April, Gerrit Pape wrote:
> I was hoping there're other
> contributors appearing, so I can learn from their questions, and jump in
> when time permits.
Makes sense.
Previous proposals
~~~~~~~~~~~~~~~~~~
Thorsten's proposal [quoted in 13]:
Concurrent upload of all shells, with Breaks: old versions of
other shells.
Shared debconf template and scripts to turn it into reality.
The shared template would have permitted values: 'unchanged'
'dash' 'bash' 'mksh' 'ksh93' 'posh'.
Upgrade code works like this: drop all diversions. Update
symlink. Add diversion if some package wants to ship /bin/sh.
Sounds good, but it does not address how bash can lose /bin/sh
without causing breakage during the upgrade.
Raphael's proposal [13]:
bash loses /bin/sh! Like so:
- dash's preinst is rewritten in C, so it does not require
/bin/sh initially.
- bash's postinst removes any diversion from dash, if present,
taking care to preserve /bin/sh.
- dash's preinst still adds a diversion, to make room for its
/bin/sh.
- bash pre-depends on this version of dash.
- Any shell except dash that wants to divert /bin/sh has to
predepend on this bash version; doing so makes everything okay.
- Any shell that wants to divert /bin/sh, including bash, does
so with a debconf prompt after it is installed.
Presumably the idea is that before bash is updated, its /bin/sh is
always diverted, so the removal of bash's copy of /bin/sh causes
no harm.
I don't see why dash's preinst urgently has to be rewritten in C
(though I don't disagree that it's a good thing to do); if /bin/bash
is missing, aren't we in deep trouble anyway?
Where to go from here
~~~~~~~~~~~~~~~~~~~~~
Based on the above, a possible order of operations:
I. Get rid of /bin/sh in bash.
Preinst:
1. Ensures some _other_ package (e.g., dash) diverts /bin/sh.
2. Makes sure /bin/sh points to the same place at the
beginning and end.
Files list: removes /bin/sh
The result is that /bin/sh is unchanged and that (if anything
does) dash nominally provides /bin/sh. The next time dash is
unpacked, it would overwrite /bin/sh.
II. Teach dash to cope with (I).
Precondition: /bin/sh exists.
Preinst:
1. Reads /bin/sh to determine who should provide it.
2. Set up the corresponding diversion.
Files list: /bin/sh -> dash
Rationale: Resetting the /bin/sh diversion before unpacking
dash prevents the problem described in (I).
III. Teach bash to avoid the problem with (I).
Pre-Depends: dash (>= the version from (II))
Thoughts? Questions? Advice?
Thanks,
Jonathan
A somewhat orthogonal task
~~~~~~~~~~~~~~~~~~~~~~~~~~
IV. Introduce a new package to take responsibility for the /bin/sh symlink.
Preinst (not necessarily in this order):
1. Removes all diversions
2. Sets up a diversion
3. Makes sure /bin/sh points to the same place at the
beginning and end.
Debconf prompt lets a person choose what shell to use.
Postinst makes sure /bin/sh points to the configured place.
It is be hard to get this right while avoiding file conflicts
until only one package provides /bin/sh, but it should be possible
to experiment on lenny.
V. Teach shells to rely on the package from (IV) for configuration.
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