[Bug 1594658] Re: diskless setup with nfs mounted home hangs on shutdown/reboot

[Paul Crawford]

We were seeing this on a fresh Ubuntu 16.04 64-bit installation using
fixed IP addresses and automounter for NFS drives. The suggestion #7
seems to fix it for use, but it would be useful to know just what is
happening with the script. Is it trawling through some user's home
directory when expanding the '~*' entry in the case statement in
/sbin/resolvconf by any chance?

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https://bugs.launchpad.net/bugs/1594658

Title:
  diskless setup with nfs mounted home hangs on shutdown/reboot

Status in nfs-utils package in Ubuntu:
  Confirmed
Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  Ubuntu 16.04 fresh install hangs when shutting down.
  The system is diskless PXE-booted with a couple of nfs mounted directories including homedir.

  As I have no persistent storage whatsoever, I don't have any logs, but
  in debug-shell, running journalctl -f I can see that it hangs at

  [   *] (1 of 2) A stop job running for Raise Network Interfaces (10s / 1min 30s)Jun 20 20:23:05 $hostname kernel: nfs: server $nfs-ip-address not responding, still trying
  Jun 20 20:23:05 $hostname kernel: nfs: server $nfs-ip-address not responding, still trying
  Jun 20 20:23:14 $hostname kernel: nfs: server $nfs-ip-address not responding, still trying
  Jun 20 20:24:08 $hostname kernel: nfs: server $nfs-ip-address not responding, still trying

  Second job in "(1 of 2)" is thermald, turning it off does not fix the problem.
  Also, this counter "(10s / 1min 30s)" stops visually updating.

  server $nfs-ip-address is not responding, because, all network
  interfaces are already down at this point.

  I am not exactly sure why this happens. Looks like there is a wrong
  ordering of shutdown of systemd services, which bring down interfaces
  before something nfs-related, but I am not sure if that's the reason
  of hanging.

  
  Workaround that fixes the problem:
  In /lib/systemd/system/networking.service
  comment following line:
  ExecStop=/sbin/ifdown -a --read-environment

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