[Bug 1566508] Re: autofs races with sssd on startup

[Maciej Puzio]

Victor, you are right saying that we are dealing with more than one bug
here. It appears to me that we have 3 or 4 separate bugs all conspiring
to prevent autofs from starting in the configuration as described above.
I think that the "setautomntent" error message is a symptom of a
different bug than the one causing the "no mounts in table" error. I
experienced both problems in Trusty/upstart, but so far only the
"setautomntent" bug in Xenial/Systemd/autofs-with-SysV. According to my
tests, the "setautomntent" bug is caused by sssd starting before network
is ready, while "no mounts in table" results from sssd reaching ready
state before its responders are up. However, Xenial startup is a total
mess, and I am still trying to figure out what is really happening, so I
may be wrong in the details.

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Title:
  autofs races with sssd on startup

Status in autofs package in Ubuntu:
  Confirmed
Status in sssd package in Ubuntu:
  Confirmed

Bug description:
  This report concerns a configuration where autofs and sssd are both
  installed, sssd is configured to provide automount maps, and
  nsswitch.conf directs autofs to use sssd. In such a configuration
  autofs often fails on boot complaining "no mounts in table". This is
  because autofs may be started before sssd, or after sssd is started
  but before its autofs support is ready. If this happens, one can
  restart autofs and it will work fine.

  This bug affects other users:
  * Bug 40189 "autofs needs to be restarted to pick up some shares" - a very old bug with invalid status, but see last comment #46, complaining about Ubuntu trusty: https://bugs.launchpad.net/ubuntu/+source/autofs/+bug/40189/comments/46
  * Link to SSSD-users mailing list, also complaining about Ubuntu trusty: https://lists.fedorahosted.org/pipermail/sssd-users/2015-July/003166.html

  $ lsb_release -rd
  Description:    Ubuntu 14.04.4 LTS
  Release:        14.04

  $ apt-cache policy autofs sssd
  autofs:
    Installed: 5.0.7-3ubuntu3.2
  sssd:
    Installed: 1.11.5-1ubuntu3

  $ uname -a
  Linux **** 3.13.0-83-generic #127-Ubuntu SMP Fri Mar 11 00:25:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

  Workaround:
  Edit /etc/init/autofs as shown in attached files (both full file and diff provided). Unfortunately, this modification will work only in this particular configuration, thus it is not a good candidate for a patch. 
  Explanation:
  We have to deal with two problems here:
  1. Autofs starts on runlevel [2345], and in effect its startup order in relation to sssd is random. We fix this by changing start stanza to "start on started sssd".
  2. Unfortunately this is not enough, because sssd emits started event too early, before its autofs support is ready. To work around this, we add a loop to pre-start script that waits for sssd to start listening on /var/lib/sss/pipes/autofs.

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