[Bug 1623383] Re: Some restarts fail due to missing base devices

[Stefan Bader]

Changing the type of systemd-modules-load from oneshot to simple might
work around the problem. At least this output looks like it would have
been a hang:

* systemd-modules-load.service - Load Kernel Modules
   Loaded: loaded (/lib/systemd/system/systemd-modules-load.service; static; vendor preset: enabled)
   Active: active (exited) since Fri 2016-09-23 09:57:49 BST; 5h 12min ago
     Docs: man:systemd-modules-load.service(8)
           man:modules-load.d(5)
 Main PID: 546 (code=exited, status=0/SUCCESS)
    Tasks: 0 (limit: 4915)
   Memory: 0B
      CPU: 0
   CGroup: /system.slice/systemd-modules-load.service

Sep 23 09:57:57 kernel02 systemd[1]: systemd-modules-load.service: Failed to send unit remove signal for systemd-modules-load.service: Transport endpoint is not connected
Sep 23 09:57:57 kernel02 systemd[1]: systemd-modules-load.service: Changed dead -> exited

I can ssh into the system and netstat -an shows something listening on
/run/systemd/provate

netstat -an|grep private
unix  2      [ ACC ]     STREAM     LISTENING     31143    /run/user/1000/systemd/private
unix  2      [ ACC ]     STREAM     LISTENING     9536     /run/systemd/private

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https://bugs.launchpad.net/bugs/1623383

Title:
  Some restarts fail due to missing base devices

Status in udev package in Ubuntu:
  Confirmed

Bug description:
  Arch: s390x
  Release: Yakkety / 16.10

  This happens on some (but not all) system starts with Yakkety. In
  Xenial (which is using the same 4.4 kernel version the Yakkety systems
  were using when the problem was first observed) this did not happen.
  The system (LPAR) this was seen first was an upgrade from Xenial but
  since then has been freshly installed with Yakkety. The same behaviour
  is seen on a zVM guest running Yakkety.

  The attached syslog shows a failed boot, followed by one that did work. Note the "Found device .*(sclp|encc00).*" messages in the good boot. Those are missing in the bad attempt and as a result networking and console fail to be usable. Also note, those boots were 4.8 kernels but we saw this with 4.4 kernels, too.
  This might be a systemd problem / race, I just filed it into udev for now as that better matches the not finding basic devices symptom.

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