[Bug 2128606] Re: Correctly copy Architecture-Variant field

Thu Oct 23 08:17:40 UTC 2025

Manual test case before and after, with after reverting back to amd64.

Before: It is broken, no Architecture-Variant registered

root at deef22dfcf58:/# apt  policy apt
apt:
  Installed: 3.1.6ubuntu2
  Candidate: 3.1.6ubuntu2
  Version table:
 *** 3.1.6ubuntu2 500
        500 http://archive.ubuntu.com/ubuntu questing/main amd64 Packages
        100 /var/lib/dpkg/status
root at deef22dfcf58:/#
root at deef22dfcf58:/# export DEBIAN_FRONTEND=noninteractive
root at deef22dfcf58:/# apt -o APT::Architecture-Variants=amd64v3 -U install apt
[...]
Fetched 22.4 MB in 2s (14.8 MB/s)
56 packages can be upgraded. Run 'apt list --upgradable' to see them.
Upgrading:
  apt

Summary:
  Upgrading: 1, Installing: 0, Removing: 0, Not Upgrading: 55
  Download size: 1439 kB
  Space needed: 20.5 kB / 8224 MB available

Get:1 http://archive.ubuntu.com/ubuntu questing/main amd64v3 apt amd64 3.1.6ubuntu2 [1439 kB]
Fetched 1439 kB in 1s (2474 kB/s)
(Reading database ... 5217 files and directories currently installed.)
Preparing to unpack .../apt_3.1.6ubuntu2_amd64v3.deb ...
Unpacking apt (3.1.6ubuntu2) over (3.1.6ubuntu2) ...
Setting up apt (3.1.6ubuntu2) ...
Processing triggers for libc-bin (2.42-0ubuntu3) ...
root at deef22dfcf58:/# apt -o APT::Architecture-Variants=amd64v3 policy apt
apt:
  Installed: 3.1.6ubuntu2
  Candidate: 3.1.6ubuntu2
  Version table:
     3.1.6ubuntu2 500
        500 http://archive.ubuntu.com/ubuntu questing/main amd64v3 Packages
 *** 3.1.6ubuntu2 100
        100 /var/lib/dpkg/status
root at deef22dfcf58:/# dpkg --status apt | grep ^Arch
Architecture: amd64

After: Architecture-Variant is correctly registered
[...]
Setting up dpkg (1.22.21ubuntu3.1) ...
root at deef22dfcf58:/# apt -o APT::Architecture-Variants=amd64v3 -U install apt
[...]
Fetched 22.6 MB in 3s (7880 kB/s)
65 packages can be upgraded. Run 'apt list --upgradable' to see them.
Upgrading:
  apt

Summary:
  Upgrading: 1, Installing: 0, Removing: 0, Not Upgrading: 64
  Download size: 1439 kB
  Space needed: 20.5 kB / 8140 MB available

Get:1 http://archive.ubuntu.com/ubuntu questing/main amd64v3 apt amd64 3.1.6ubuntu2 [1439 kB]
19% [1 apt 347 kB/1439 kB 24%]
Fetched 1439 kB in 1s (1314 kB/s)
(Reading database ... 8961 files and directories currently installed.)
Preparing to unpack .../apt_3.1.6ubuntu2_amd64v3.deb ...
Unpacking apt (3.1.6ubuntu2) over (3.1.6ubuntu2) ...
Setting up apt (3.1.6ubuntu2) ...
Processing triggers for libc-bin (2.42-0ubuntu3) ...
root at deef22dfcf58:/# apt policy apt
apt:
  Installed: 3.1.6ubuntu2
  Candidate: 3.1.6ubuntu2
  Version table:
 *** 3.1.6ubuntu2 100
        100 /var/lib/dpkg/status
root at deef22dfcf58:/# apt -o APT::Architecture-Variants=amd64v3 policy apt
apt:
  Installed: 3.1.6ubuntu2
  Candidate: 3.1.6ubuntu2
  Version table:
 *** 3.1.6ubuntu2 500
        500 http://archive.ubuntu.com/ubuntu questing/main amd64v3 Packages
        100 /var/lib/dpkg/status
root at deef22dfcf58:/# dpkg --status apt | grep ^Arch
Architecture: amd64
Architecture-Variant: amd64v3

Back to v1 also works correctly and drops it:

root at deef22dfcf58:/# apt install -U apt
[...]
Fetched 22.7 MB in 2s (14.0 MB/s)
8 packages can be upgraded. Run 'apt list --upgradable' to see them.
Upgrading:
  apt

Summary:
  Upgrading: 1, Installing: 0, Removing: 0, Not Upgrading: 7
  Download size: 1432 kB
  Freed space: 20.5 kB

Get:1 http://archive.ubuntu.com/ubuntu questing/main amd64 apt amd64 3.1.6ubuntu2 [1432 kB]
Fetched 1432 kB in 1s (1373 kB/s)
(Reading database ... 8961 files and directories currently installed.)
Preparing to unpack .../apt_3.1.6ubuntu2_amd64.deb ...
Unpacking apt (3.1.6ubuntu2) over (3.1.6ubuntu2) ...
Setting up apt (3.1.6ubuntu2) ...
Processing triggers for libc-bin (2.42-0ubuntu3) ...
root at deef22dfcf58:/# apt  policy apt
apt:
  Installed: 3.1.6ubuntu2
  Candidate: 3.1.6ubuntu2
  Version table:
 *** 3.1.6ubuntu2 500
        500 http://archive.ubuntu.com/ubuntu questing/main amd64 Packages
        100 /var/lib/dpkg/status
root at deef22dfcf58:/# dpkg --status apt | grep ^Arch
Architecture: amd64

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https://bugs.launchpad.net/bugs/2128606

Title:
  Correctly copy Architecture-Variant field

Status in dpkg package in Ubuntu:
  Fix Released
Status in dpkg source package in Questing:
  Fix Committed
Status in dpkg source package in Resolute:
  Fix Released

Bug description:
  [Impact]
  amd64v3 packages are differentiated from amd64 packages by

  Architecture-Variant: amd64v3

  When APT sees amd64v3 packages, it considers them an upgrade to amd64
  packages, so when amd64v3 is enabled, a dist-upgrade first upgrades
  you to amd64v3.

  Inadvertently, dpkg did not copy the field when installing the
  package, causing apt to consider the installed amd64v3 package as
  amd64 again, and the next dist-upgrade trying to "upgrade" them again.

  [Test plan]
  Check that the field appears in dpkg --status when installing an amd64v3 package
  Check that the field disappears in dpkg --status when installing an amd64 package.

  If no amd64v3 packages are involved the field always remains NULL (no
  Architecture-Variant is written to the status file); so no visible
  change is seen on any system in the real world now; as amd64v3 is opt-
  in and not yet announced.

  Do a release-upgrade in a lxd container with the new dpkg available
  and installed during the upgrade; vs a lxd container without the new
  dpkg, and ensure there are no regressions.

  [Where problems could occur]
  The field could be garbage if not initialized (covered by "install an amd64 package"). The default value of the field is NULL; this is not a concern:

  The field is used here:

  src/deb/build.c
  487:                 pkg->available.arch_variant ? pkg->available.arch_variant : pkg->available.arch->name, DEBEXT);

  ^ this is unaffected by the change as available always contains the
  field if availabe

  lib/dpkg/parse.c
  66:  { FIELD("Architecture-Variant"),      f_charfield,       w_charfield,      PKGIFPOFF(arch_variant)   },

  - w_charfield will now write that field if set (it checks if the field
  value is null and skips it, which always happened so far)

  src/main/unpack.c
  908:  pkg->installed.arch_variant = pkg->available.arch_variant;

  ^ here we copy the available value to the installed database, this is
  the new line. It's a no-op everywhere that doesn't have amd64v3
  packages about to be installed (copying default NULL to NULL, nothing
  else set the field of course).

  lib/dpkg/dpkg-db.h
  124:  const char *arch_variant;

  ^ declaration of the field inside the struct

  The only thing that reads the field outside of dpkg is apt when it
  sees if the installed version is the same as an available version:
  There it checks if they have matching variants. A variant is always
  preferred over an architecture.

  If no variants where ever configured or force-installed, variants do
  not appear anywhere on the system.

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