[Bug 1996489] Re: The unminimize command fails to reinstall packags with missing files in the `share` and `locale` directories

[Ferenc Wágner]

I think the main problem with the unminimize script in jammy and later
is that dpkg 1.21 changed the way it reports missing files: instead of
reporting a checksum failure (..5......) it explicitly says "missing"
since https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=963087 was
implemented, breaking the unminimize logic entirely, as demonstrated by
/usr/share/doc/libprocps8/NEWS.Debian.gz still being missing at the end
of

$ docker run --rm -it ubuntu:jammy sh -c 'yes | unminimize; dpkg
--verify libprocps8'

This affects all packages having anything besides their copyright and
changelog under /usr/share/doc but having no man pages nor localization.

The above also explains why unminimize uses different logic for
different files: the changelog and copyright files are always kept
around, while manuals and localization files are excluded entirely.

The ugly but harmless errors from dpkg -S could be avoided by simply
using the --no-run-if-empty option of xargs.

xargs should automatically take care of not exceeding the argument
length limit of the system, so I assume the comment mentioning that is
stale.

** Bug watch added: Debian Bug tracker #963087
   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=963087

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https://bugs.launchpad.net/bugs/1996489

Title:
  The unminimize command fails to reinstall packags with missing files
  in the `share` and `locale` directories

Status in cloud-images:
  New
Status in livecd-rootfs package in Ubuntu:
  Confirmed

Bug description:
  I am building a custom Docker image based on:

      https://github.com/microsoft/vscode-dev-
  containers/tree/main/containers/ubuntu

  I added a line that runs `yes | unminmize':

  https://github.com/nomirose/devcontainer/commit/1ba51c651c06b9ce71c73e7bf016939d989cfa2c#diff-4c1f94864a9642897e2fa6c1d532830b6d1a2ba9d6b6f2f149178dde32cf0e77R10-R11

  Here's from build log :

  https://github.com/nomirose/devcontainer/actions/runs/3451129967/jobs/5760151170#step:6:1565

  And here are the errors from the `uminmize` command:

      #9 47.54 Reinstalling packages with system documentation in /usr/share/doc/ ..
      #9 48.76 dpkg-query: error: --search needs at least one file name pattern argument
      #9 48.76
      #9 48.76 Use --help for help about querying packages.
      #9 48.80 Reading package lists...
      #9 49.49 Building dependency tree...
      #9 49.62 Reading state information...
      #9 49.76 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
      #9 49.76 Restoring system translations...
      #9 50.97 dpkg-query: error: --search needs at least one file name pattern argument
      #9 50.97
      #9 50.97 Use --help for help about querying packages.
      #9 51.01 Reading package lists...
      #9 51.71 Building dependency tree...
      #9 51.85 Reading state information...
      #9 52.00 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
      #9 53.18 Documentation has been restored successfully.
      #9 DONE 54.3s

  Specifically, the error is:

      dpkg-query: error: --search needs at least one file name pattern
  argument

  I copped `/usr/local/sbin/unminimize` to my local directory to see if
  I could debug what was doing on.

  When looking for packages with missing files in the `/usr/bin/man`
  directory, the script does this:

      dpkg -S /usr/share/man/ |sed 's|, |\n|g;s|: [^:]*$||' |
  DEBIAN_FRONTEND=noninteractive xargs apt-get install --reinstall -y

  However, for the `/usr/share/docs/` the script does this:

      dpkg --verify --verify-format rpm | awk '/..5......   \/usr\/share\/doc/ {print $2}' | sed 's|/[^/]*$||' | sort |uniq \
          | xargs dpkg -S | sed 's|, |\n|g;s|: [^:]*$||' | uniq | DEBIAN_FRONTEND=noninteractive xargs apt-get install --reinstall -y

  The script runs the same command for the `/usr/share/locale/`
  directory.

  In both cases, no packages ever make it to the `xargs dpkg -S`
  command, so the script throws an error. However, because the error
  occurs in a pipe, it is lost, and the script continues despite the
  `set -e` at the start (which is a bug in itself).

  However, with a little experimentation, I found that the original
  command for `/usr/local/bin` works perfectly for the
  `/usr/share/docs/` and `/usr/share/locale/` directories.

  Why not run the same command for all three directories? You could even
  wrap it in a function.

  However, you could improve performance by combining all three into a
  single command.

  The `unminimize` script notes:

      # Reinstallation takes place in two steps because a single dpkg --verified
      # command generates very long parameter list for "xargs dpkg -S" and may go
      # over ARG_MAX. Since many packages have man pages the second download
      # handles a much smaller amount of packages.

  I understand the concern about hitting `ARG_MAX`, but I think a better
  solution to that problem would be to use `xargs -n` to set a limit on
  the maximum number of arguments. This change would allow xargs to run
  `dpkg -S` as many times as need (to avoid hitting ARG_MAX).

  Doing it this way would also speed up the script.

  There are many packages with missing files in multiple minmized
  directories, meaning that as it stands, even if the bug was fixed,
  some packages would be re-installed twice, maybe even three times.

  (I have seen this for myself because I essentially wrote a shorter
  version of the script for my own use.)

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