Re: Repeatable builds using pkgbase

On Mon, 21 Aug 2023 at 17:26, Doug Rabson <dfr@rabson.org> wrote:

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> On Mon, 21 Aug 2023 at 17:23, Baptiste Daroussin <bapt@freebsd.org> wrote:
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>> On Mon, Aug 21, 2023 at 02:33:24PM +0100, Doug Rabson wrote:
>> > While working on build scripts for FreeBSD container images, I wanted to
>> > get to the point where my builds are repeatable, i.e. if I create two
>> > images with the same set of packages installed in the same order, they
>> > should be identical.
>> >
>> > The main stumbling block is timestamps. I can force all the file
>> timestamps
>> > to a fixed value with buildah using the '--timestamp' argument to either
>> > 'buildah commit' or 'buildah build' but even then, the two images have
>> > different hashes. Looking deeper, the difference is in
>> > /var/db/pkg/local.sqlite. If I compare SQL dumps of the databases from
>> each
>> > image, I can see a timestamp embedded in the sqlite file:
>> >
>> > diff dump1 dump2
>> >
>> >
>> > 4c4
>> > < INSERT INTO packages
>> > VALUES(1,'base','FreeBSD-zoneinfo','13.2p2','zoneinfo package','zoneinfo
>> > package',NULL,NULL,'FreeBSD:13:amd64','re@FreeBSD.org','
>> > https://www.FreeBSD.org
>> >
>> ','/',731014,0,0,1,1692446701,'2$2$c9w95oqai9bwhny1k4pcg8mji77xgk43zjxxb69j1duzq5jao18wak4deer85epmfpc8ngyysyt9wu74pg7sczkqc3ekyawkfgwzi8d',NULL,NULL,0);
>> > ---
>> > > INSERT INTO packages
>> > VALUES(1,'base','FreeBSD-zoneinfo','13.2p2','zoneinfo package','zoneinfo
>> > package',NULL,NULL,'FreeBSD:13:amd64','re@FreeBSD.org','
>> > https://www.FreeBSD.org
>> >
>> ','/',731014,0,0,1,1692622924,'2$2$c9w95oqai9bwhny1k4pcg8mji77xgk43zjxxb69j1duzq5jao18wak4deer85epmfpc8ngyysyt9wu74pg7sczkqc3ekyawkfgwzi8d',NULL,NULL,0);
>> >
>> >
>> > Looking at the pkg source, I can see that the prepared statement for
>> > inserting into the packages table explicitly uses NOW() for this column.
>> > Would it be reasonable to allow changing this, e.g. by adding a command
>> > line argument to pkg to override the default? I haven't tried this to
>> see
>> > if that makes the two databases identical - if not, I guess I'll just
>> > remove pkg metadata altogether.
>>
>> yes this would be reasonable, if you use en env var, please respect
>> SOURCE_DATE_EPOCH.
>>
>> I'll try this out, probably using an env var as you suggest. Hopefully
> there is nothing non-deterministic in sqlite which would stop this from
> being reproducible.
>

Sadly, even if I override the timestamp written to the packages table, the
resulting local.sqlite files on two consecutive runs are still different.
If I compare the two using 'sqlite3 local.sqlite .dump', the sql dumps are
identical so there is something else in sqlite which is making things
non-reproducible. I guess I'll have to fall back to plan B and remove the
package metadata from my images.

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