[Bug 1930573] Please test proposed package

[Brian Murray]

Hello Mathieu, or anyone else affected,

Accepted usrmerge into hirsute-proposed. The package will build now and
be available at
https://launchpad.net/ubuntu/+source/usrmerge/24ubuntu3.1 in a few
hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
hirsute to verification-done-hirsute. If it does not fix the bug for
you, please add a comment stating that, and change the tag to
verification-failed-hirsute. In either case, without details of your
testing we will not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

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https://bugs.launchpad.net/bugs/1930573

Title:
  usrmerge error after upgradingfrom 20.10 to 21.04

Status in usrmerge package in Ubuntu:
  Fix Committed
Status in usrmerge source package in Hirsute:
  Fix Committed
Status in usrmerge source package in Impish:
  Fix Committed
Status in usrmerge source package in Jammy:
  Fix Committed
Status in usrmerge package in Debian:
  Unknown

Bug description:
  [Impact]

   * Starting with Ubuntu Hirsute, the 'usrmerge' package is pulled into
  the default installation, doing the merging of /{bin,sbin,lib}/ and
  /usr/{bin,sbin,lib} on upgrade. If there are left-over generated files
  it will fail with an error like this:

  Setting up usrmerge (24ubuntu3) ...

  FATAL ERROR:
  Both /lib/udev/hwdb.bin and /usr/lib/udev/hwdb.bin exist.

  
  The upgrade has completed but there were errors during the upgrade 
  process. 

   * We want a fix in Hirsute+ that clears the old location (e.g.
  /lib/udev/hwdb.bin) if the file has already been re-generated at the
  new location (e.g. /usr/lib/udev/hwdb.bin).

  
  [Test Plan]

  Prepare a recent, but non-usrmerge'd system (e.g. launch Bionic and upgrade to Focal then Hirsute):
  $ lxc launch ubuntu:bionic usrmerge
  # do-release-upgrade
  [...]
  # reboot
  # ls -la / # to make sure that /lib is not (yet) a link to /usr/lib

  Simulate duplicated generated files & upgrade:
  # mkdir -p /usr/lib/udev && cp /lib/udev/hwdb.bin /usr/lib/udev/
  # vim /etc/update-manager/release-upgrades # change to "Prompt=normal"
  # do-release-upgrade
  [...]
  => Upgrade fails, press "C" to cancel bug report
  => "The upgrade has completed but there were errors during the upgrade process."

  Verify that the script still fails:
  # /usr/lib/usrmerge/convert-usrmerge
  FATAL ERROR:
  Both /lib/udev/hwdb.bin and /usr/lib/udev/hwdb.bin exist.

  Install relevant usrmerge package:
  # wget https://launchpad.net/ubuntu/+archive/primary/+files/usrmerge_VER_all.deb
  # dpkg -i usrmerge_VER_all.deb
  => The system has been successfully converted.
  # /usr/lib/usrmerge/convert-usrmerge
  => The system has been successfully converted.
  # echo $?
  0

  [Where problems could occur]

   * The upload modifies the convert-usrmerge script, adding special handling for certain, generated files.
   * If something goes wrong, it could delete the wrong state of udev's hwdb which would be re-generated by systemd-hwdb-update.service
   * It could also interrupt the upgrade processes on installation of the usrmerge package, asking the user for manual action (e.g. solving some file conflict and re-running /usr/lib/usrmerge/convert-usrmerge)

  [Other Info]
   
   * The patch was sent to Debian: https://bugs.debian.org/997866

  
  === Original Description ===

  I got the following error after upgrading from 20.10 to 21.04:

  Setting up usrmerge (24ubuntu3) ...

  FATAL ERROR:
  Both /lib/udev/hwdb.bin and /usr/lib/udev/hwdb.bin exist.

  You can try correcting the errors reported and running again
  /usr/lib/usrmerge/convert-usrmerge until it will complete without errors.
  Do not install or update other Debian packages until the program
  has been run successfully.

  dpkg: error processing package usrmerge (--configure):
   installed usrmerge package post-installation script subprocess returned error exit status 1
  Errors were encountered while processing:
   usrmerge

  Running "sudo dpkg --configure -a", "sudo apt -f install" or "sudo
  /usr/lib/usrmerge/convert-usrmerge" give exactly the same error.

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