[Bug 1546214] Re: Docker containers lose their cgroup after systemd reload

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: docker.io (Ubuntu)
       Status: New => Confirmed

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Title:
  Docker containers lose their cgroup after systemd reload

Status in docker.io package in Ubuntu:
  Confirmed
Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  
  After a Systemd reload & any service restart, docker top no longer show process of containers:

  To reproduce this issue, do the following step:

  # docker run -d --name test busybox sleep 1d
  # docker top test
  UID                 PID                 PPID                C                   STIME               TTY                 TIME                CMD
  root                26416               1072                1                   18:05               ?                   00:00:00            sleep 1d
  # systemctl --system daemon-reload && systemctl restart atd.service
  # docker top test
  UID                 PID                 PPID                C                   STIME               TTY                 TIME                CMD
  [  no process listed... but sleep is still running]

  Note: this idea of restarting any service restart come from patch
  https://lists.freedesktop.org/archives/systemd-
  devel/2014-September/023276.html (which is applied to Systemd package
  in Ubuntu)

  
  After few searching, this seems to be due to process from the container being moved in other cgroup by Systemd. More details on https://github.com/docker/docker/issues/20152

  Depending on version of Systemd (Wily or Xenial), this issue:

  * Wily: Happend with Docker 1.10 (with default option)
  * Wily: Does NOT happend with Docker 1.10 and --exec-opt native.cgroupdriver=systemd
  * Wily: Does NOT happend with Docker 1.9
  * Xenial: Does always happend (Docker 1.9, 1.10 with or without native.cgroupdriver=systemd)

  
  I don't know if this issue is a Systemd issue, a Docker issue... or in middle.

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