Crossgrading support (was Re: Y2038 - best way forward in Debian?)
Adam Borowski wrote:
>On Wed, Feb 12, 2020 at 06:10:53PM +0000, Steve McIntyre wrote:
>>
>> /me ponders - this could be a fun task for a GSoC/outreachy student to
>> hack on, maybe?
>
>Prior art:
>
>* my unfinished https://github.com/kilobyte/crossgrade -- does a lot of
> error checking and continue-after-problem, but currently stops after
> crossgrading the essential set
>
>* stuff linked from https://wiki.debian.org/CrossGrading
Ah, cool!
>Problems:
>
>* crossgrades fail _badly_ in a hard to recover way if packages for the
> two architectures come in different versions (including binNMUs). This
> hurts especially if -ports archs are involved.
Yup. Probably best done on top of a stable release, by default, to
avoid the worst of this,
>* arch-specific or local packages are not as bad but 1. crossgrade must
> know what's safe to remove, 2. what should be left unchanged (and their
> recursive deps unremoved), 3. there may be non-multiarchable packages
> within 1. or 2.'s dependency chain
Yup. So I think it would be good to have a tool which can work through
the existing state of a system up-front and analyse what's likely to
work or not.
>* systemd can't handle being crossgraded (I'm a systemd hater, but same was
> noticed by eg. anarcat and Simon Richter). On a minimal system it may
> survive but usually it starts killing daemons (including X), unmounting
> stuff, choking and forcing an unclean reboot, etc. This could be worked
> around by:
> â?¢ switching to sysvinit
> â?¢ booting from a different media then chrooting to crossgrade (not for
> ordinary users unless it's eg. scripted from d-i)
> â?¢ having a package bring a grub entry that boots with
> init=/usr/sbin/crossgrade to do the thing?
ACK. Booting in a *simple* state is likely to be key.
--
Steve McIntyre, Cambridge, UK. steve@einval.com
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