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

[Maciej Puzio]

I finally had a chance to test this issue in Ubuntu 16.04. In a setup
described as in the bug description above, autofs still won't start
correctly, and this is a result of the whole string of problems. Most of
them appear to be separate bugs, but I will list them here for
completeness:

1. ifup returns before interface is up.
2. ifup at .service finishes before interface is up. This is for two reasons: because the service calls ifup, and because the service has wrong type (simple instead of oneshot). As a result, network-online.target is reached at a wrong time.
3. sssd.service does not wait for network-online.target.
4. autofs reverted in Xenial to a SysV-style script and does not have a systemd-style service file. Thus it is difficult to request that it is started after sssd. However, fixing #2 causes systemd to run SysV scripts much later, providing a relief for problems #4 and #5.
5. The issue being subject of this bug report is very likely still present, though I was unable to reproduce it exactly. Unfixed issue #2 caused auto fs to fail with a different error message ("setautomntent: lookup(sss): setautomntent: No such file or directory"), while fixed issue #2 hid the bug. The workaround involving waiting for sssd to start listening on /var/lib/sss/pipes/autofs can still be used for extra safety. I will test this further.

I will work more on these problems and submit bug reports for them if
they haven't been reported yet.

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https://bugs.launchpad.net/bugs/1566508

Title:
  autofs races with sssd on startup

Status in autofs package in Ubuntu:
  New
Status in sssd package in Ubuntu:
  New

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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