[Bug 1555237] Re: Upgrade from 14.04.4→ 16.04 dies midway taking out the session.

[Martin Pitt]

Mathieu found the culprit, many thanks! This is due to some cleanup code
in udevd which wreaks havoc when not running under systemd, as it
assumes that it runs in its own cgroup (normally /system.slice/systemd-
udevd.service). src/udev/udevd.c on_post() has:

                       } else if (manager->cgroup)
                                /* cleanup possible left-over processes in our cgroup */
                                cg_kill(SYSTEMD_CGROUP_CONTROLLER, manager->cgroup, SIGKILL, false, true, NULL);

But under upstart processes don't run in cgroups, and hence
manager->cgroup is (almost surely) "/" and thus it kills all running
processes. We need to disarm this to only clean up if the cgroup is not
empty.

This can be reproduced fairly easily:

  - Boot a trusty VM (cloud-image/autopkgtest image is fine)
  - Install udisks2
  - Change apt sources to xenial, install udev from xenial
  - apt-get install --reinstall udisks2

The last command triggers udev rules and causes most processes to get
killed and restarted, which can be seen nicely in their startup time and
in /var/log/syslog.

** Changed in: systemd (Ubuntu)
    Milestone: None => ubuntu-16.04

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Title:
  Upgrade from 14.04.4→ 16.04 dies midway taking out the session.

Status in dbus package in Ubuntu:
  In Progress
Status in systemd package in Ubuntu:
  In Progress
Status in ubuntu-release-upgrader package in Ubuntu:
  Invalid

Bug description:
  STEPS:
  1. Install 14.04.4 on a uefi securebooted system
  2. update it
  3. Install openssh-server for debug access
  4. reboot
  5. Hit alt+f2
  6. Type update-manager -d and hit enter

  EXPECTED:
  I expected a smooth transition to 16.04

  ACTUAL:
  System is completely taken out mid way through the process killing the session and x also no tty when hitting ctrl+alt+f1-6

  ---

  TESTS RESULTS (from cyphermox):

  On amd64 (no EFI) under qemu/libvirt, qxl graphics:
  - upgrading just libglib2.0-0 from 16.04 on top of 14.04.4: PASS
  - upgrading ubuntu-desktop (running gnome-shell) 14.04.4 to 16.04: PASS
  - upgrading ubuntu-desktop (running xubuntu-session) 14.04.4 to 16.04: PASS
  - manually upgrading compiz and other packages to 16.04 versions; after adding xenial sources:
    - compiz and related packages (http://paste.ubuntu.com/15415280/) : PASS
    - xserver-xorg and related: PASS
    - unity and related: PASS
    - ubuntu-desktop: PASS
    - libgl1-mesa-dri: PASS
    - apt-get dist-upgrade: FAIL (screensaver may have kicked in)
  - standard upgrading 14.04.4 to 16.04; screensaver disabled: FAIL (looked fine, but upgrade eventually froze, might well be a different issue)
  - re-enabling screensaver after upgrade, before reboot: TODO (above failed)

  On ppc64el:
  - upgrading ubuntu-server 14.04.4 -> 16.04: PASS

  ---

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: ubuntu-release-upgrader-core 1:0.220.8
  ProcVersionSignature: Ubuntu 4.2.0-30.36~14.04.1-generic 4.2.8-ckt3
  Uname: Linux 4.2.0-30-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.19
  Architecture: amd64
  CrashDB: ubuntu
  Date: Wed Mar  9 17:01:27 2016
  InstallationDate: Installed on 2016-03-04 (5 days ago)
  InstallationMedia: Ubuntu 14.04.4 LTS "Trusty Tahr" - Beta amd64 (20160224)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  Symptom: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to xenial on 2016-03-09 (0 days ago)
  VarLogDistupgradeTermlog:

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