Bug#919915: grub2-common: fails to upgrade from 'stretch-backports' - trying to overwrite /etc/kernel/postinst.d/zz-update-grub from grub-cloud-amd64 0.0.4~bpo9+1

[Andreas Beckmann <anbe@debian.org>]

Hi,

On 2019-01-20 23:03, Colin Watson wrote:
> On Sun, Jan 20, 2019 at 10:08:46PM +0100, Bastian Blank wrote:
>> On Sun, Jan 20, 2019 at 05:46:27PM +0000, Colin Watson wrote:
> Ah, yes, I'd forgotten about #910959.
> 
> Why don't you ship the files under different names, though?  There's no
> reason they have to be called "zz-update-grub".  The worst consequence
> of e.g. "zz-update-grub-cloud-amd64" would be possibly running
> update-grub more than once during upgrade, which is certainly better
> than hijacking another package's conffile.  Even that shouldn't happen
> much in practice as grub-cloud-amd64/stretch-backports conflicts with
> most of the other packages one is likely to install that ship
> zz-update-grub, and you could just leave those conflicts in place in
> stretch-backports if you were concerned about multiple runs of
> update-grub.
> 
> A workable approach would be:
> 
>  * 0.0.4~bpo9+2 in stretch-backports moves the conffile to a
>    non-colliding name
>  * 0.0.4.1 (or whatever) in buster removes that non-colliding name on
>    upgrade
> 
> I could probably put together NMU patches for you if you don't have the
> time.
> 
>>> I'm happy to add Breaks/Replaces, but first the version of
>>> grub-cloud-amd64 in stretch-backports needs to be fixed to stop
>>> hijacking grub2-common's conffiles.

since grub-cloud-amd64 does not seem to get improved in
stretch-backports, could we please have B+R in grub2-common to fix
upgrades to buster?

>>>  After that has been done, I would
>>> be happy to add Breaks/Replaces on grub-cloud-amd64 (<< fixed-version).
>>
>> There is not way to define Breaks/Replaces relations that only match on
>> the package variant in backports.
> 
> Why would that be necessary?  If you can confirm that >= 0.0.4 isn't
> going to have this problem, then Breaks/Replaces grub-cloud-amd64 (<<
> 0.0.4) in grub2-common would surely be fine;

I just verified in piuparts that adding
  Breaks+Replaces: grub-cloud-amd64 (<< 0.0.4)
to grub2-common fixes the file overwrite issue on upgrades from
stretch-backports to buster.


Andreas