ubuntu-cpc lacks common function to reverse setup_mountpoint

[Robert C Jennings]

[SRU Justification]
After the move of livefs builds to lxd containers and use of --rbind with /dev, cloud image builds fail where setup_mountpoint was called from the common functions. There is no related teardown for this common function so extra binary hooks that called setup_mountpoint were forced to duplicate the cleanup locally which became out of sync with the setup.

This change adds a common function called teardown_mountpoint to reverse the operations performed by setup_mountpoint and makes use of that new function.

[Test case]
Daily images on cloud-images.ubuntu.com are currently failing to build as a result of this bug. The daily images are built using a private overlay on top of the livecd-rootfs in the archive, so unfortunately we can't describe directly a public end-to-end test case for this.

We will verify this fix by verifying that we are able to produce daily cloud images again for each of the releases.

[Regression potential]
For xenial we should also verify this change by doing a test build of all images against xenial-proposed to guard against any possible regressions.
For zesty, there are no ongoing builds of any projects other than cloud images so there is no risk of external regressions.

[Robert C Jennings (rcj)]

Attaching a patch to add a teardown_mountpoint function to reverse the actions taken by setup_mountpoint.

[Brian Murray (brian-murray)]

Hello Robert, or anyone else affected,

Accepted livecd-rootfs into zesty-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/livecd-rootfs/2.441.6 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-zesty to verification-done-zesty. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-zesty. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Brian Murray (brian-murray)]

Hello Robert, or anyone else affected,

Accepted livecd-rootfs into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/livecd-rootfs/2.408.17 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-xenial to verification-done-xenial. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-xenial. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Launchpad Janitor (janitor)]

This bug was fixed in the package livecd-rootfs - 2.455

---------------
livecd-rootfs (2.455) artful; urgency=medium

  * Restore the call to 'umount -R $mountpoint' from umount_partition,
    accidentally dropped in previous upload.

 -- Steve Langasek <email address hidden> Wed, 13 Sep 2017 12:50:10 -0700

[Robert C Jennings (rcj)]

Marking xenial as verification failed. I have been able to test on xenial and it failed quickly.

Our first call to 'udevadm settle' in our first binary hook fails:
+ teardown_mountpoint binary/boot/filesystem.dir
+ local mountpoint=binary/boot/filesystem.dir
+ umount binary/boot/filesystem.dir/var/cache/apt
+ umount binary/boot/filesystem.dir/var/lib/apt
+ umount binary/boot/filesystem.dir/tmp
+ umount binary/boot/filesystem.dir/sys
+ umount binary/boot/filesystem.dir/proc
+ umount -R binary/boot/filesystem.dir/dev
+ udevadm settle
config/functions: line 107: udevadm: command not found
E: config/hooks/030-root-tarball.binary failed (exit non-zero). You should check for errors.

In a prior good build we see that we had not been calling udevadm until after the first call to mount_image in the common functions. We were getting udev installed as a side-effect of a call to install kpartx:
+ mount_image binary/boot/disk.ext4 1
+ apt-get install -qqy kpartx
Selecting previously unselected package udev.

I have a possible fix @ http://bazaar.launchpad.net/~rcj/livecd-rootfs/xenial-proposed/revision/1420 but I'm unable to test before I'm out of the office (and the builders have a spectacular backlog currently of ~9hrs).

[Steve Langasek (vorlon)]

Accepted a new livecd-rootfs into -proposed with the proposed fix for this latest problem, and resetting verification state.

[Dan Watkins (oddbloke)]

I've successfully built new images with the livecd-rootfs in xenial-proposed.

[Launchpad Janitor (janitor)]

This bug was fixed in the package livecd-rootfs - 2.408.18

---------------
livecd-rootfs (2.408.18) xenial; urgency=medium

  [ Robert C Jennings ]
  * Install udev before calls to udevadm

 -- Steve Langasek <email address hidden> Wed, 13 Sep 2017 22:10:11 -0700

[Łukasz Zemczak (sil2100)]

Could we get the zesty packages tested as well? There is a second livecd-rootfs SRU pending and blocked by the zesty one in -proposed.

[Chris Glass (tribaal)]

I've successfully built new images with the livecd-rootfs in zesty-proposed.

Marking verification-done.

[Launchpad Janitor (janitor)]

This bug was fixed in the package livecd-rootfs - 2.441.8

---------------
livecd-rootfs (2.441.8) zesty; urgency=medium

  [ Robert C Jennings ]
  * Install udev before calls to udevadm

 -- Steve Langasek <email address hidden> Wed, 13 Sep 2017 22:27:45 -0700