From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: Timestamps in tarballs created by 'patch-and-repack'
Date: Wed, 15 Jul 2015 16:30:19 +0200
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In-Reply-To: <87lheithka.fsf@netris.org> (Mark H. Weaver's message of "Tue, 14
	Jul 2015 20:01:25 -0400")
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To: Mark H Weaver <mhw@netris.org>
Cc: guix-devel@gnu.org

Mark H Weaver <mhw@netris.org> skribis:

> Mark H Weaver <mhw@netris.org> writes:
>
>> Mark H Weaver <mhw@netris.org> writes:
>>
>>> However, this raises a deeper problem: all of the outputs of
>>> 'patch-and-repack' contain non-deterministic timestamps, and these
>>> timestamps can cause problems with future builds.
>>>
>>> Would it be sufficient to simply zero out all of the timestamps before
>>> repacking?
>>
>> I looked into this a bit more.  In addition to timestamps, the other
>> impure bits getting into tar files are the names and numeric ids of the
>> owner and groups.  Section 4.3.1 (Overriding File Metadata) of the GNU
>> tar manual describes how to override these when creating an archive.
>>
>> My guess is that the following options would be sufficient to make the
>> generated tar archives deterministic:
>>
>>   --mtime=3D@0 --owner=3Droot:0 --group=3Droot:0
>
> This seems to work well, so I've added these flags when creating
> tarballs in commits 2e9511dfbdb5ddd78c2f205c4ca7fc23738d79f8 and
> c09e6a5f5e2a77beff89d68069f3037c1b6310e5 in core-updates.

That sounds like the right thing (it=E2=80=99s also what is used in
gnu/system/install.scm for the binary tarball.)

Thanks for noticing and fixing it!

Ludo=E2=80=99.