[Bug 974584] Re: Semaphores cannot be created in lxc container

[Steve Langasek]

I think there are the following possible valid end states that we want
to get to at the end of the postinst:

 - we're not in a chroot.  /dev/shm is bind mounted to /run/shm, with the reboot script handling the fix-up to make /dev/shm a symlink to /run/shm before next boot.
 - we're in a chroot and /dev is not bind mounted.  sysvshm should be mounted *somewhere* within the chroot, but we don't know where this will be done and we're not going to do it ourselves.  So dictate that this should be /run/shm, and make /dev/shm a symlink there.
 - we're in a chroot and /dev is bind mounted, and /dev/shm is a symlink to /run/shm (because the parent environment is also a recent Debian/Ubuntu release).  Make the /run/shm directory.
 - we're in a chroot, /dev is bind mounted, and /dev/shm is also bind mounted.  This is not a good situation to be in, because it means that the future correctness of the chroot is dependent on the setup remaining the same on the host system - which it won't if the host system is an older Debian/Ubuntu release that is later upgraded.  But we do the best we can for now, and make /run/shm a symlink to /dev/shm.
 - we're in a chroot, /dev/ is bind mounted, and /dev/shm is a non-bind-mounted directory.  We can't fix this, so we should just create the /run/shm directory and leave /dev/shm alone.

Does that make sense?

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https://bugs.launchpad.net/bugs/974584

Title:
  Semaphores cannot be created in lxc container

Status in Launchpad itself:
  Invalid
Status in “lxc” package in Ubuntu:
  Fix Released
Status in “sysvinit” package in Ubuntu:
  Triaged
Status in “lxc” source package in Precise:
  Fix Released
Status in “sysvinit” source package in Precise:
  Triaged
Status in “lxc” source package in Quantal:
  Fix Released
Status in “sysvinit” source package in Quantal:
  Triaged
Status in “sysvinit” package in Debian:
  New

Bug description:
  >>> from multiprocessing import synchronize
  >>> synchronize.Lock()
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    File "/usr/lib/python2.6/multiprocessing/synchronize.py", line 117, in __init__
      SemLock.__init__(self, SEMAPHORE, 1, 1)
    File "/usr/lib/python2.6/multiprocessing/synchronize.py", line 49, in __init__
      sl = self._semlock = _multiprocessing.SemLock(kind, value, maxvalue)
  OSError: [Errno 38] Function not implemented

  Thanks to hallyn, there's a workaround and a fix: adding this line to the container's fstab will fix the problem:
  none dev/shm tmpfs defaults 0 0

  He is updating the ubuntu template with this change.

  Original bug report description was Launchpad related (celery tests
  fail on parallel testing instances)

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