[Bug 1555760] Re: Too many levels of symbolic links /proc/sys/fs/binfmt_misc

[Martin Pitt]

I tried to reproduce this with the standard images.linuxcontainers.org
trusty container image, on both a wily and a xenial host, but this
doesn't happen with obvious steps (otherwise we would have noticed this
much earlier already).

>From the github issue I take it you are using Ubuntu wily -- which lxd
package version do you use? The 0.20-0ubuntu4.1 shipped in Wily or some
backport? I tried the wily version and that does not even work any more
("error: json: cannot unmarshal string into Go value of type int64" when
trying to list or launch from images:), and there's no newer version in
wily-backports.

How exactly did you create the container?

How often does this happen, under the same circumstances? Is this a race
condition which only happens sometimes, or is this always reproducible?
Can you reproduce this with running

    sudo systemctl stop proc-sys-fs-binfmt_misc.mount
    lxc launch [...]

several times? Stopping proc-sys-fs-binfmt_misc.mount will stop the
actual mount and go back to systemd providing a "proxy" mount until the
first access.

Please give me the output of "systemctl status proc-sys-fs-
binfmt_misc.mount" and "mount | grep binfmt" before and after the failed
"lxc launch".

Does it always work after the first failure and after
/proc/sys/fs/binfmt_misc actually gets mounted?

** Changed in: systemd (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1555760

Title:
   Too many levels of symbolic links /proc/sys/fs/binfmt_misc

Status in binfmt-support package in Ubuntu:
  New
Status in systemd package in Ubuntu:
  Incomplete

Bug description:
  At first I thought this was an LXD issue, but it turns out the issue
  is in systemd

  https://github.com/lxc/lxd/issues/1727#issuecomment-194416558

  ls -l  /proc/sys/fs/binfmt_misc  fails with error:

  Too many levels of symbolic links

  
  I restarted binfmt manually by running:

      sudo /usr/sbin/update-binfmts --disable
      sudo /usr/sbin/update-binfmts --enable

  I think using systemd to do this would have also worked:

      sudo service binfmt-support restart

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