** Description changed:

  [SRU Justification]
  When booted without an initramfs, the root device will be /dev/root, not a
  named device. There is partial support for this when resizing filesystems,
  but not for growing partitions, without which it doesn't do much good.
  
  A system boots significantly slower with an initramfs than without, and
  we care about boot speed; a user should not have to have to boot with an
  initramfs to take advantage of root partition resizing.
  
  [Test case]
  Because there are not yet any official Ubuntu images that boot without 
initramfs, the test case is somewhat opaque.  Here is a test case that should 
work with public branches, though I will be doing validation in GCE using a 
private branch.
  1. Build livecd-rootfs from lp:~vorlon/livecd-rootfs/minimizing/ and upload 
it to a ppa.
  2. bzr branch lp:launchpad-buildd
  3. run the following setup commands:
  export BUILDID=cloud-init-test
  export CHROOT_ROOT=$HOME/build-$BUILDID/chroot-autobuild
  wget 
http://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-amd64-root.tar.xz
 -O /tmp/root.tar.xz
  mkdir -p $CHROOT_ROOT/build
  tar -C $CHROOT_ROOT -x -f /tmp/root.tar.xz
  rm $CHROOT_ROOT/etc/resolv.conf
  launchpad-buildd/mount-chroot $BUILDID
  launchpad-buildd/update-debian-chroot $BUILDID
  4. Run a build without -proposed enabled:
  launchpad-buildd/buildlivefs --arch amd64 --project ubuntu-cpc --subproject 
minimize --series <release> --build-id $BUILDID --image-target=none
  5. Boot the resulting image 
($HOME/build-$BUILDID/chroot-autobuild/build/binary/boot/disk.ext4) in an 
openstack environment.
  6. Verify that the image boots but does not expand the root partition.
  7. Run a build again with -proposed enabled:
  launchpad-buildd/buildlivefs --arch amd64 --project ubuntu-cpc --subproject 
minimize --series <release> --build-id $BUILDID --image-target=none --proposed
  8. Boot the resulting image in an openstack environment.
  9. Verify that the image boots, and that this time the root partition is 
expanded to use the full disk.
  
  [Regression potential]
  Users with existing initramfsless images that are configured with the default 
of resizing the root partition may be surprised when this starts to work.  
However, this only applies to first boot of an image, so only newly-mastered 
images would be affected, so this should be caught by any image CI before the 
affected users put such an image into production if it has serious impact for 
them.
+ 
+ 
+ Related bugs:
+  * bug 1684869: growing root partition does not always work with 
root=PARTUUID=

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https://bugs.launchpad.net/bugs/1677376

Title:
  growing partitions does not work when booted without initramfs

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