[Bug 2043820] Re: Unable to contact snap store on Xubuntu from Jammy to Noble

[Nick Rosbrook]

** Description changed:

+ [Impact]
+ 
+ Upgrades from Jammy to Noble can fail if snap transition packages are
+ installed after the new systemd has been unpacked, but before systemd-
+ resolved has been unpacked.
+ 
+ In practice, this manifests on at least Xubuntu upgrades during the
+ chromium-browser snap transition.
+ 
+ [Test Plan]
+ 
+ Without this fix, the snap store connectivity check will fail when
+ installing the chromium-browser snap because systemd-resolved is not
+ present, so DNS lookups fail during the connectivity check.
+ 
+ With the fix in place, the systemd-resolved stub resolver should be
+ disabled during the upgrade so that DNS lookups succeed even when
+ systemd-resolved is not yet unpacked on the system again.
+ 
+ So, to test this fix, we should run an upgrade on a Xubuntu 22.04
+ system:
+ 
+ $ do-release-upgrade -d
+ 
+ And verify that (a) the chromium-browser installation (and snap store
+ connectivity check) succeeds, and (b) that the stub resolver is not in
+ use during the upgrade.
+ 
+ $ cat /etc/resolv.conf
+ $ cat /run/systemd/resolved.conf.d/dist-upgrade-no-stub-resolver.conf
+ 
+ [Where problems could occur]
+ 
+ This patch disables the systemd-resolved stub resolver by writing a drop-in to
+ /run/systemd/resolved.conf.d. If there was a mistake in the drop-in, it would not correctly disable the stub resolver.
+ 
+ [Original Description]
+ 
  When running `do-release-upgrade -d` on Jammy Xubuntu, the upgrade fails
  consistently at the `Installing the firefox snap` step.
  
  This was first detected on Jenkins [1], then reproduced locally with
  `auto-upgrade-testing`, then finally by manually running a `do-release-
  upgrade -d` in a VM.
  
  [1]: https://platform-qa-jenkins.ps5.ubuntu.com/view/upgrade-
  list/job/upgrade_ubuntu-jammy-noble-xubuntu-amd64_qemu/7/consoleFull
  (Jenkins full log attached)
  
  ProblemType: Bug
  DistroRelease: Ubuntu 22.04
  Package: ubuntu-release-upgrader-core 1:22.04.17
  ProcVersionSignature: User Name 5.15.0-88.98-generic 5.15.126
  Uname: Linux 5.15.0-88-generic x86_64
  ApportVersion: 2.20.11-0ubuntu82.5
  Architecture: amd64
  CasperMD5CheckResult: unknown
  CrashDB: ubuntu
  CurrentDesktop: XFCE
  Date: Fri Nov 17 18:24:22 2023
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  Symptom: ubuntu-release-upgrader
  UpgradeStatus: No upgrade log present (probably fresh install)

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https://bugs.launchpad.net/bugs/2043820

Title:
  Unable to contact snap store on Xubuntu from Jammy to Noble

Status in firefox package in Ubuntu:
  Confirmed
Status in snapd package in Ubuntu:
  Confirmed
Status in ubuntu-release-upgrader package in Ubuntu:
  Invalid
Status in firefox source package in Noble:
  Confirmed
Status in snapd source package in Noble:
  Confirmed
Status in ubuntu-release-upgrader source package in Noble:
  Triaged

Bug description:
  [Impact]

  Upgrades from Jammy to Noble can fail if snap transition packages are
  installed after the new systemd has been unpacked, but before systemd-
  resolved has been unpacked.

  In practice, this manifests on at least Xubuntu upgrades during the
  chromium-browser snap transition.

  [Test Plan]

  Without this fix, the snap store connectivity check will fail when
  installing the chromium-browser snap because systemd-resolved is not
  present, so DNS lookups fail during the connectivity check.

  With the fix in place, the systemd-resolved stub resolver should be
  disabled during the upgrade so that DNS lookups succeed even when
  systemd-resolved is not yet unpacked on the system again.

  So, to test this fix, we should run an upgrade on a Xubuntu 22.04
  system:

  $ do-release-upgrade -d

  And verify that (a) the chromium-browser installation (and snap store
  connectivity check) succeeds, and (b) that the stub resolver is not in
  use during the upgrade.

  $ cat /etc/resolv.conf
  $ cat /run/systemd/resolved.conf.d/dist-upgrade-no-stub-resolver.conf

  [Where problems could occur]

  This patch disables the systemd-resolved stub resolver by writing a drop-in to
  /run/systemd/resolved.conf.d. If there was a mistake in the drop-in, it would not correctly disable the stub resolver.

  [Original Description]

  When running `do-release-upgrade -d` on Jammy Xubuntu, the upgrade
  fails consistently at the `Installing the firefox snap` step.

  This was first detected on Jenkins [1], then reproduced locally with
  `auto-upgrade-testing`, then finally by manually running a `do-
  release-upgrade -d` in a VM.

  [1]: https://platform-qa-jenkins.ps5.ubuntu.com/view/upgrade-
  list/job/upgrade_ubuntu-jammy-noble-xubuntu-amd64_qemu/7/consoleFull
  (Jenkins full log attached)

  ProblemType: Bug
  DistroRelease: Ubuntu 22.04
  Package: ubuntu-release-upgrader-core 1:22.04.17
  ProcVersionSignature: User Name 5.15.0-88.98-generic 5.15.126
  Uname: Linux 5.15.0-88-generic x86_64
  ApportVersion: 2.20.11-0ubuntu82.5
  Architecture: amd64
  CasperMD5CheckResult: unknown
  CrashDB: ubuntu
  CurrentDesktop: XFCE
  Date: Fri Nov 17 18:24:22 2023
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  Symptom: ubuntu-release-upgrader
  UpgradeStatus: No upgrade log present (probably fresh install)

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