[Bug 1778817] Re: release upgrade from xenial to bionic desktop: screen locks itself, password to unlock fails

[Brian Murray]

I tested a release upgrade from Ubuntu 16.04 to Ubuntu 18.04 today using
the version of release-upgrader in -proposed and the lock screen did not
appear.

bdmurray at clean-xenial-amd64:/tmp/u-r-u$ grep "release-upgrader version" /var/log/dist-upgrade/main.log 
2018-07-16 14:00:39,174 INFO release-upgrader version '18.04.21' started


** Tags removed: verification-needed verification-needed-bionic
** Tags added: verification-done verification-done-bionic

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https://bugs.launchpad.net/bugs/1778817

Title:
  release upgrade from xenial to bionic desktop: screen locks itself,
  password to unlock fails

Status in compiz package in Ubuntu:
  New
Status in ubuntu-release-upgrader package in Ubuntu:
  Fix Released
Status in compiz source package in Bionic:
  New
Status in ubuntu-release-upgrader source package in Bionic:
  Fix Committed

Bug description:
  [Impact]
  During a release upgrade, the screen should not be locked because the upgrade of underlying libraries may leave the system in an inconsistent state where the process locking the screen may not be able to unlock it again. (Its possible for the screen to lock during the fetching process before the call to inhibitIdle happens.)

  [Test Case]
  1) Configure a screen lock with a short time period (1 minute) and ensure it'll take more than 1 minute to fetch all the packages
  2) Upgrade an Ubuntu 16.04 system to Ubuntu 18.04
  3) Observe the screen locks during the upgrade process

  With the version of ubuntu-release-upgrader from -proposed the screen
  will not lock during the fetching process. I wasn't able to recreate
  the bug where the system would not unlock but testing that the screen
  doesn't lock should be sufficient to verify this.

  [Regression Potential]
  Code is just being moved from DistUpgradeQuirks.py to DistUpgradeController.py but its possible a mistake was made so this should be tested carefully.

  [Original Description]
  There is code in the ubuntu-release-upgrader to handle this (DistUpgrade/DistUpgradeQuirks.py:DistUpgradeQuirks._inhibitIdle).

  I have just started a release upgrade of an Ubuntu desktop from xenial
  to bionic with update-manager -d.  After leaving it unattended for a
  while, I came back to find the screen was locked.

  /var/log/auth.log includes messages such as:

  Jun 26 16:00:45 epona compiz: PAM unable to dlopen(pam_unix.so):
  /lib/security/pam_unix.so: cannot open shared object file: No such
  file or directory

  This indicates a problem dlopen()ing the PAM modules (actual path:
  /lib/x86_64-linux-gnu/security/pam_unix.so) because some ABI has
  changed in the system libraries, and the copy loaded into the running
  compiz process does not have the symbols required in order to run this
  module.

  This is the exact reason the screensaver is supposed to be inhibited
  on upgrade.

  This is also why every sensible screensaver spawns a fresh helper
  process to handle the authentication through PAM.  compiz (unity),
  apparently, does not.

  I do not yet know what symbols have changed to cause this failure.
  I'm still investigating that.

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