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Re: Unreproducible «When Docker images become fixed-point»?
From: |
Ludovic Courtès |
Subject: |
Re: Unreproducible «When Docker images become fixed-point»? |
Date: |
Tue, 05 Jul 2022 09:44:37 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.1 (gnu/linux) |
Hi,
zimoun <zimon.toutoune@gmail.com> skribis:
>> A possible reason why we’re building a different derivation than back
>> then is provenance info: as explained under ‘--save-provenance’ in the
>> manual, provenance info is not “canonical” and we could end up including
>> different provenance info. I don’t have any clear scenario in mind but
>> that sounds plausible.
>
> I do not understand why provenance is not deterministic. I mean I
> understand that two provenances can build the same pack, but I miss why
>
> guix time-machine -C channels.scm \
> -- pack -f docker --save-provenance -m manifest.scm
>
> is not building the same pack for the exact same channels.scm and
> manifest.scm files. Why the resulting provenance info should be
> different?
I don’t know either, but that’s the only plausible scenario I can think
of. We would need the original .drv or the original pack to compare.
> Maybe there is bug in how the provenance is managed; but I do not think
> it comes from this part. Instead, I vaguely think the bug is from
> elsewhere – dependent on filesystem or unsorted list or other creative
> ideas. :-)
No, no: the store file names differ. That means we’re building
different derivations in the first place.
> Well, let save some data, replay this scenario 6 months later and
> investigate. :-) Keep you in touch.
Yeah.
Another approach is to take the derivation returned by
guix time-machine --commit=fb32a38db1d3a6d9bc970e14df5be95e59a8ab02 -- \
pack -f docker --save-provenance python python-numpy -d
and to look for things that might vary between invocations or call
sites: provenance data, imported modules, (guix config) details,
whatever.
Thinking about it, (guix config) is one possible source of discrepancy:
it captures sysconfdir and localstatedir, so you’ll get a different
result if you have different settings. The defaults are:
(define-public %localstatedir "/var")
(define-public %sysconfdir "/etc")
Could it be that you had something different back then?
Ludo’.