[Bug 2036195] Re: Any packages installed in binary hooks are marked as manually installed - even dependencies

[Philip Roche]

As there will be no further uploads accepted for xenial and bionic the
proposed changes @ https://code.launchpad.net/~philroche/livecd-
rootfs/+git/livecd-rootfs/+ref/bugfix/ubuntu-cpc-LP-2036195-auto-
installed-packages-xenial for xenial and
https://code.launchpad.net/~philroche/livecd-rootfs/+git/livecd-
rootfs/+ref/bugfix/ubuntu-cpc-LP-2036195-auto-installed-packages-bionic
for bionic have been merged to https://code.launchpad.net/~ubuntu-core-
dev/livecd-rootfs/+git/livecd-rootfs/+ref/ubuntu/xenial and
https://code.launchpad.net/~ubuntu-core-dev/livecd-rootfs/+git/livecd-
rootfs/+ref/ubuntu/bionic respectively, but there will be no
corresponding package upload.

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https://bugs.launchpad.net/bugs/2036195

Title:
  Any packages installed in binary hooks are marked as manually
  installed - even dependencies

Status in livecd-rootfs package in Ubuntu:
  Fix Released
Status in livecd-rootfs source package in Xenial:
  Fix Committed
Status in livecd-rootfs source package in Bionic:
  Fix Committed
Status in livecd-rootfs source package in Focal:
  Fix Committed
Status in livecd-rootfs source package in Jammy:
  Fix Committed
Status in livecd-rootfs source package in Lunar:
  Fix Committed

Bug description:
  After much debugging trying to understand why `apt-get autoremove` was
  not working in a binary hook I realised that all packages installed in
  a binary hook are marked as manually installed - even the dependencies
  of packages. This is a bug.

  Another side affect of this is that any dependency of a package in the
  base chroot that is removed in a binary hook is not autoremovable in
  the binary hook.

  It is autoremovable once the image is created and launched though.

  This is due to how the `setup_mountpoint` function works (see
  https://git.launchpad.net/livecd-rootfs/tree/live-
  build/functions#n123) specifically

  ```
  mount -t tmpfs none "$mountpoint/var/lib/apt"
  ```

  Which means that inside the chroot that the binary hook works on, the
  `/var/lib/apt` directory is empty... including the
  `/var/lib/apt/extended_states` file which is used to store whether a
  package was auto installed or not.

  The same goes the other way - any changes to the
  `/var/lib/apt/extended_states`  file inside chroot that the binary
  hook is changing are not reflected in the final image due to the
  `teardown_mountpoint` (see https://git.launchpad.net/livecd-
  rootfs/tree/live-build/functions#n152) not persisting any of those
  changes.

  The end result being.

  * If a package is removed in the binary hook then the resulting image will likely have autoremovable packages at first launch
  * Any package and their dependencies installed in a binary hook will all be marked as manually installed.

  SRU
  ====

  [ Impact ]

   * Packages installed in a binary hook are marked as manually
  installed - even the dependencies of packages

  [ Test Plan ]

   * Build test images and remove a package with dependencies. 
     * Confirm that the dependencies are marked as autoremovable.
     * Confirm there are packages marked as auto installed

  [ Where problems could occur ]

   * Is any dependent packages are not marked as autremovable. 
   * If no packages are marked as auto installed

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