[Bug 2080233] Re: do-release-upgrade fails when snap returns non-zero exit code [[wsl] do-release-upgrade fails with systemd disabled]

Mon Apr 14 16:55:02 UTC 2025

> Such errors currently are fatal to the upgrade, but they should not
be.

Why should snap errors not be fatal to an upgrade? Many applications on
a typical ubuntu system are snaps nowadays.

What's the risk of continuing a release upgrade when such errors are
ignored? What are the consequences?

Or is the statement from the bug too broad an incorrect, since we are
just ignoring all errors around the "snap debug connectivity" call?

I think we need a test plan that will do a release upgrade of a normal
desktop system with the usual snaps installed, and simulating the snap
store connectivity error, so that self._snapstore_reachable is false.
And then someway to check that the upgrade finished correctly, even
without the snaps being considered.

** Changed in: ubuntu-release-upgrader (Ubuntu Oracular)
       Status: New => Incomplete

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to ubuntu-release-upgrader in
Ubuntu.
https://bugs.launchpad.net/bugs/2080233

Title:
  do-release-upgrade fails when snap returns non-zero exit code [[wsl]
  do-release-upgrade fails with systemd disabled]

Status in ubuntu-release-upgrader package in Ubuntu:
  Fix Released
Status in ubuntu-release-upgrader source package in Noble:
  New
Status in ubuntu-release-upgrader source package in Oracular:
  Incomplete

Bug description:
  [Impact]

  There are various setups where snap will not behave as expected, such
  as in WSL or chroot environments. There are currently quirks in
  ubuntu-release-upgrader that are not resilient to general snap
  failures.

  Such errors currently are fatal to the upgrade, but they should not
  be.

  [Test Plan]

  Test #1

  In an Ubuntu container, simulate snap errors by "removing" snap:

  $ mv /usr/bin/snap /usr/bin/.snap

  Then, attempt an upgrade. Without a patch, the upgrade will fail
  early:

  $ do-release-upgrade

  [...]

  Reading package lists... Done    
  Building dependency tree... Done 
  Reading state information... Done

  Traceback (most recent call last):
    File "/tmp/ubuntu-release-upgrader-ihkoc99x/noble", line 8, in <module>
      sys.exit(main())
    File "/tmp/ubuntu-release-upgrader-ihkoc99x/DistUpgrade/DistUpgradeMain.py", line 241, in main
      if app.run():
    File "/tmp/ubuntu-release-upgrader-ihkoc99x/DistUpgrade/DistUpgradeController.py", line 2662, in run
      return self.fullUpgrade()
    File "/tmp/ubuntu-release-upgrader-ihkoc99x/DistUpgrade/DistUpgradeController.py", line 2467, in fullUpgrade
      if not self.doPostInitialUpdate():
    File "/tmp/ubuntu-release-upgrader-ihkoc99x/DistUpgrade/DistUpgradeController.py", line 1438, in doPostInitialUpdate
      self.quirks.run("PostInitialUpdate")
    File "/tmp/ubuntu-release-upgrader-ihkoc99x/DistUpgrade/DistUpgradeQuirks.py", line 102, in run
      func()
    File "/tmp/ubuntu-release-upgrader-ihkoc99x/DistUpgrade/DistUpgradeQuirks.py", line 143, in noblePostInitialUpdate
      self._checkStoreConnectivity()
    File "/tmp/ubuntu-release-upgrader-ihkoc99x/DistUpgrade/DistUpgradeQuirks.py", line 661, in _checkStoreConnectivity
      connected = Popen(["snap", "debug", "connectivity"], stdout=PIPE,
    File "/usr/lib/python3.10/subprocess.py", line 971, in __init__
      self._execute_child(args, executable, preexec_fn, close_fds,
    File "/usr/lib/python3.10/subprocess.py", line 1863, in _execute_child
      raise child_exception_type(errno_num, err_msg, err_filename)
  FileNotFoundError: [Errno 2] No such file or directory: 'snap'

  With a patch in place, the error should be logged instead, and the upgrade should continue.

  Test #2 (from Noble only, not necessary from Jammy b/c TPM FDE does
  not exist there)

  Ensure that the fix does not regress the quirk on TPM FDE systems.
  Create a 24.04 LTS VM, select hardware-backed full disk encryption in
  the installer. Then, attempt an upgrade with:

  $ do-release-upgrade --proposed

  The upgrade should still be blocked.

  [Where problems could occur]

  This patch changes an existing quirk designed to prevent unsupported
  upgrades on TPM FDE systems. An incorrect patch could regress that
  quirk. To mitigate this, Test #2 above verifies the quirk still works
  as intended.

  [Original Description]

  Original report: https://github.com/ubuntu/WSL/issues/493

  On WSL, systemd is not always enabled. This is the case on WSL1 where
  it cannot be enabled and on WSL2 when it's been disabled or not
  enabled by default.

  When systemd is not available do-release-upgrade fails with the error
  below and upgrade is cancelled:

  From the report
  ===
  Traceback (most recent call last):
    File "/tmp/ubuntu-release-upgrader-uqmd8iby/noble", line 8, in <module>
      sys.exit(main())
    File "/tmp/ubuntu-release-upgrader-uqmd8iby/DistUpgrade/DistUpgradeMain.py", line 241, in main
      if app.run():
    File "/tmp/ubuntu-release-upgrader-uqmd8iby/DistUpgrade/DistUpgradeController.py", line 2642, in run
      return self.fullUpgrade()
    File "/tmp/ubuntu-release-upgrader-uqmd8iby/DistUpgrade/DistUpgradeController.py", line 2447, in fullUpgrade
      if not self.doPostInitialUpdate():
    File "/tmp/ubuntu-release-upgrader-uqmd8iby/DistUpgrade/DistUpgradeController.py", line 1438, in doPostInitialUpdate
      self.quirks.run("PostInitialUpdate")
    File "/tmp/ubuntu-release-upgrader-uqmd8iby/DistUpgrade/DistUpgradeQuirks.py", line 102, in run
      func()
    File "/tmp/ubuntu-release-upgrader-uqmd8iby/DistUpgrade/DistUpgradeQuirks.py", line 127, in noblePostInitialUpdate
      self._test_and_fail_on_tpm_fde()
    File "/tmp/ubuntu-release-upgrader-uqmd8iby/DistUpgrade/DistUpgradeQuirks.py", line 1898, in _test_and_fail_on_tpm_fde
      snap_list = subprocess.check_output(['snap', 'list'])
    File "/usr/lib/python3.10/subprocess.py", line 421, in check_output
      return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
    File "/usr/lib/python3.10/subprocess.py", line 526, in run
      raise CalledProcessError(retcode, process.args,
  subprocess.CalledProcessError: Command '['snap', 'list']' returned non-zero exit status 1.
  """

  This error should be ignored when systemd is not running.

  Read https://github.com/ubuntu/WSL/issues/493#issuecomment-2324510606
  for details. Thanks to Vadim for the investigation.

  """
  In /tmp/ubuntu-release-upgrader-t8sg0mg9/DistUpgrade/DistUpgradeQuirks.py:

       def _test_and_fail_on_tpm_fde(self):
          """
          LP: #2065229
          """
          try:
              snap_list = subprocess.check_output(['snap', 'list'])
              snaps = [s.decode().split()[0] for s in snap_list.splitlines()]
          except FileNotFoundError:
              # snapd not installed?
              return
  I think except FileNotFoundError: should be extended to except:

  Because DistUpgradeQuirks.py is stored in some temp directory, it was hard to change it inplace, but I succeeded, and then the upgrade process continued as it should
  ===

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/2080233/+subscriptions