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Bug#746578: libpam-systemd to flip dependencies - proposal



On Sat, 1 Nov 2014 18:55:32 +0000 Ian Jackson <ijackson@chiark.greenend.org.uk> wrote:
> Rationale (Constitution 6.1(5)):
> 
> 1. Currently libpam-systemd (which is pulled in by quite a few
>    dependency chains) Depends on `systemd-sysv | systemd-shim'.

Here, you give the simplified dependency without the version constraint,
while below you give the full Depends with version constraint.  Please
choose one or the other and use it consistently.

> 2. The effect of this is that installing certain leaf packages which
>    depend on libpam-systemd can cause a user's init system to be
>    switched to systemd, even on systems where a user has deliberately
>    chosen not to use the default init system, and even when the switch
>    is unnecessary.

Nit: s/certain leaf//; the packages depending on libpam-systemd are not
actually leaf packages, and in fact various other packages depend on
them.

> 3. Swappping the order of these dependencies would avoid that and has
>    no harmful effect.

I would suggest expanding on what "no harmful effect" means here: "In
particular, on systems that already have systemd-sysv installed,
libpam-systemd will still not pull in systemd-shim, thus minimizing the
risk of breakage on systemd systems.  However, on systems that
intentionally do not have systemd installed, the installation of
libpam-systemd will then prefer to pull in systemd-shim and keep the
installed init system rather than switching to systemd-sysv."

Stating that explicitly in the rationale, to set expectations, seems
preferable to a vague "no harmful effect" that does not fully make sense
without reading the full history in the bug.  TC decisions should be
self-contained.

> Decision (Constitution 6.1(4)):
> 
> 4. We therefore overrule the decision of the maintainer of
>    libpam-systemd binary package.  The Depends entry
>       systemd-sysv | systemd-shim (>= 8-2)
>    should be replaced by 
>       systemd-shim (>= 8-2) | systemd-sysv

I think this decision needs to explicitly state that it does not require
any particular version numbers in the versioned dependencies, only the
specific order.  In particular, if libpam-systemd needs to increase its
versioned dependency on systemd-shim, or if it ever needs to add a
versioned dependency on systemd-sysv, that change should not violate
this TC decision.

> Release (Constitution  6.1(5)):
> 
> 5. We request that the Release Team allow this change to into jessie.
>    (This request should be conveyed to the Release Team, after the
>    change is in unstable, by filing an unblock request in the usual
>    way.)

Is this point necessary?  The freeze has not yet occurred, and I don't
see any obvious reason why the TC needs to explicitly direct the release
team here.

- Josh Triplett


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