[Bug 1060404] Re: update-grub runs and fails in containers

[Serge Hallyn]

@Henning,

At one point we thought a workaround was to have devtmpfs mounted in the
container.  However that is a bad thing to do as changes in the
container's /dev will be reflected in the host's /dev.

So the only workaround right now (until grub is fixed in precise) is to
check (with 'mount') which device / is mounted from in the container,
and then create that device in the container.

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https://bugs.launchpad.net/bugs/1060404

Title:
  update-grub runs and fails in containers

Status in “grub2” package in Ubuntu:
  Fix Released
Status in “lxc” package in Ubuntu:
  Fix Released
Status in “grub2” source package in Precise:
  In Progress
Status in “lxc” source package in Precise:
  Triaged
Status in “grub2” source package in Quantal:
  Fix Released
Status in “lxc” source package in Quantal:
  Fix Released

Bug description:
  [Impact] GRUB upgrades fail in containers.
  [Test Case] Upgrade the grub-pc package in a container.
  [Regression Potential] In itself, this postinst fix should be quite safe.  It's possible it won't solve the whole problem - e.g. linux-image-* upgrades calling update-grub - but I wanted to backport just what was in quantal/raring rather than getting creative in an SRU.

  [XXX edit - removed the SRU justification for lxc part.  The proposed solution
  was not safe, and was undone in a later commit.  devtmpfs cannot be mounted
  in a container, because changes under the container's /dev are then
  reflected in the host's /dev.

  If grub is installed in a container (as happens, for instance, with
  the ubuntu-cloud template) then an update of grub or linux-image will
  cause update-grub to be run.  It tries, finds it can't access the root
  device, fails, and causes the update to fail.

  It would be better for update-grub to detect that it is in a container
  and simply exit 0, so that the apt-get can succeed.  I'm attaching a
  debdiff which does that.

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