[SRU] Release minimized image related changes to Xenial

[Balint Reczey]

[Impact]

 * Ability to generate minimized images is a new feature of
   livecd-rootfs. Minimized images have smaller footprint on disk, may
   not use initramfs to boot and may have smaller RAM footprint as well.
 * Using minimal images can save bandwidth and system resources and we
   would like to make those improvements available for Xenial users.

[Test Case]

 * A new autopkgtest (minimized) was added to test building minimized
   images. The test logs show the generated image sizes for ubuntu-cpc
   images with and without minimization and the minimized images have
   to be smaller.

[Regression Potential]

 * The changes should not affect images which are not minimized but the
   minimized images may not boot on some systems. For example the Linux
   kernel does not boot in a Vagrant VM without initramfs, but the
   minimized Vagrant image does not include initramfs.

 * In case the effect of changes are not limited to the minimized image
   they may make packages missing from regular images and/or may make the
   regular images unbootable.

[Other Info]

 * The current patch works around the 'minimized' autopkgtest failure on
   ppc64el which affects Artful and can be observed when the Linux kernel
   package does not depend on initramfs-tools (LP: #1700972) thus the
   minimized images don't include initramfs support.

[Balint Reczey (rbalint)]

The changes are available in the following bzr branch but I'll attach the full patch here:
https://code.launchpad.net/~ubuntu-core-dev/livecd-rootfs/xenial-proposed

[Brian Murray (brian-murray)]

Hello Balint, 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/2.408.20 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!

[Steve Langasek (vorlon)]

autopkgtests for livecd-rootfs 2.408.21 have passed for all architectures. Log for the amd64 build is here, showing the minimized test:

https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-xenial/xenial/amd64/l/livecd-rootfs/20171021_072728_a605c@/log.gz

Sizes for the unminimized (first column) vs. minimized (second column) image builds are:

277M 204M livecd.ubuntu-cpc.disk1.img
266M 195M livecd.ubuntu-cpc.disk1.vmdk
273M 202M livecd.ubuntu-cpc.ova
195M 164M livecd.ubuntu-cpc.rootfs.tar.gz
124M 100M livecd.ubuntu-cpc.rootfs.tar.xz
157M 131M livecd.ubuntu-cpc.squashfs
272M 202M livecd.ubuntu-cpc.uefi.vmdk
285M 211M livecd.ubuntu-cpc.uefi1.img
267M 197M livecd.ubuntu-cpc.vagrant.box

This is working as expected.

[Launchpad Janitor (janitor)]

This bug was fixed in the package livecd-rootfs - 2.408.21

---------------
livecd-rootfs (2.408.21) xenial; urgency=medium

  [ Balint Reczey ]
  * Use kvm kernel only on amd64.
  * Make non-x86 minimized images consistent with x86 by not explicitly
    installing the server task.
  * Clean up dangling /boot/initrd.img symlink left behind on minimized
    builds.

 -- Steve Langasek <email address hidden> Fri, 20 Oct 2017 23:10:29 -0700