Debian Bug report logs - #992647
backuppc: stores wrong path to ping6 if built on merged-/usr system

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Simon McVittie <smcv@debian.org>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: backuppc: stores wrong path to ping6 if built on merged-/usr system

Date: Sat, 21 Aug 2021 18:37:31 +0100

[Message part 1 (text/plain, inline)]

Source: backuppc
Version: 4.4.0-4
Severity: important
Tags: patch bookworm sid
User: reproducible-builds@lists.alioth.debian.org
Usertags: usrmerge
X-Debbugs-Cc: reproducible-bugs@lists.alioth.debian.org

If backuppc is built on a merged-/usr system (as created by new installations
of Debian >= 10, debootstrap --merged-usr, or installing the usrmerge
package into an existing installation), the path to ping6 is recorded in the
binary as /usr/bin/ping6.

This can be seen on the reproducible-builds.org infra:
https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/diffoscope-results/backuppc.html
(search for "ping6" to see the difference I'm concerned about).

If you have sbuild available, an easy way to reproduce this is to build
twice, once with --add-depends-arch=usrmerge and once without.

The problematic situation is if the package is *built* on a merged-/usr
system, but *used* on a non-merged-/usr system. In this situation,
/usr/bin/ping6 exists on the build system but not on the system where
backuppc will be used, resulting in the feature that uses ping6 not being
available.

Technical Committee resolution #978636 mandates heading towards a
transition to merged-/usr, and this will become a non-issue at the end of
that transition; but variation between merged-/usr and non-merged-/usr
builds is a problem while that transition is taking place, because it
can lead to partial upgrades behaving incorrectly. It is likely that
this class of bugs will become release-critical later in the bookworm
development cycle.

Some Debian developers advocate that instead of merged-/usr, we should
use a different strategy where /bin becomes a "symlink farm" with
individual symlinks such as /bin/ping6 -> /usr/bin/ping6. If that route is
taken instead of merged-/usr, then resolving bugs like this one will be
equally important as part of that transition, because it shares the
property that both /bin/ping6 and /usr/bin/ping6 exist after the transition,
but only /bin/ping6 exists on untransitioned systems.

The attached patch resolves this: with it applied, the package builds
identically with and without --add-depends-arch=usrmerge.

A side benefit of fixing this is that this change seems to be sufficient
to make the package reproducible (as recommended by Policy §4.15).

    smcv

[0001-d-rules-Specify-canonical-path-to-ping6.patch (text/x-diff, attachment)]

Message #10 received at 992647@bugs.debian.org (full text, mbox, reply):

From: Axel Beckert <abe@debian.org>

To: Simon McVittie <smcv@debian.org>, 992647@bugs.debian.org

Subject: Re: Bug#992647: backuppc: stores wrong path to ping6 if built on merged-/usr system

Date: Sun, 22 Aug 2021 12:45:04 +0200

Hi Simon,

Simon McVittie wrote:
> If backuppc is built on a merged-/usr system (as created by new installations
> of Debian >= 10, debootstrap --merged-usr, or installing the usrmerge
> package into an existing installation), the path to ping6 is recorded in the
> binary as /usr/bin/ping6.

*sigh* Thanks for the bug report.

> Technical Committee resolution #978636 mandates heading towards a
> transition to merged-/usr,

Unfortunately, yes. :-( IMHO that whole usrmerge thing is completely
unnecessary and harmful for Debian — as can be seen in this and
hundreds of other bug reports.

> From 7a89355ff53e827de8f3a5b91f7ebb79d47ad1c6 Mon Sep 17 00:00:00 2001
> From: Simon McVittie <smcv@debian.org>
> Date: Sat, 21 Aug 2021 18:26:59 +0100
> Subject: [PATCH] d/rules: Specify canonical path to ping6

Thanks for the patch.

		Regards, Axel
-- 
 ,''`.  |  Axel Beckert <abe@debian.org>, https://people.debian.org/~abe/
: :' :  |  Debian Developer, ftp.ch.debian.org Admin
`. `'   |  4096R: 2517 B724 C5F6 CA99 5329  6E61 2FF9 CD59 6126 16B5
  `-    |  1024D: F067 EA27 26B9 C3FC 1486  202E C09E 1D89 9593 0EDE

Message #17 received at 992647-close@bugs.debian.org (full text, mbox, reply):

From: Debian FTP Masters <ftpmaster@ftp-master.debian.org>

To: 992647-close@bugs.debian.org

Subject: Bug#992647: fixed in backuppc 4.4.0-5

Date: Thu, 02 Sep 2021 00:33:31 +0000

Source: backuppc
Source-Version: 4.4.0-5
Done: Axel Beckert <abe@debian.org>

We believe that the bug you reported is fixed in the latest version of
backuppc, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 992647@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Axel Beckert <abe@debian.org> (supplier of updated backuppc package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

Format: 1.8
Date: Thu, 02 Sep 2021 02:10:05 +0200
Source: backuppc
Architecture: source
Version: 4.4.0-5
Distribution: unstable
Urgency: medium
Maintainer: Debian BackupPC Team <team+pkg-backuppc@tracker.debian.org>
Changed-By: Axel Beckert <abe@debian.org>
Closes: 992647
Changes:
 backuppc (4.4.0-5) unstable; urgency=medium
 .
   [ Simon McVittie ]
   * debian/rules: Specify canonical path to ping6. (Closes: #992647)
 .
   [ Axel Beckert ]
   * Remove wrong declaration of /etc/backuppc/hosts being Perl syntax.
   * Refresh 09-hardcode-debians-rundir.patch to remove unwanted offset.
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 19a6be537cbde4540e88a1efae093b27d6469e60 59476 backuppc_4.4.0-5.debian.tar.xz
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Checksums-Sha256:
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 efb2710e7b75e990577081a63be3f3cb2e439a09401381c4df1065acd56d153a 59476 backuppc_4.4.0-5.debian.tar.xz
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 7c1f79e7e9770ed1f8e23f813c60c81c 59476 utils optional backuppc_4.4.0-5.debian.tar.xz
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