Apparmor removed on 16.04 LTS -> 18.04 upgrade

[Arni Johannesson]

Apparmor is removed when upgrading a vanilla 16.04 system to 18.04

This broke my LXD. The LXD team guided me here, per https://github.com/lxc/lxd/issues/4504

Easily solved by re-installing apparmor

[Jamie Strandboge (jdstrand)]

I tried to reproduce this and was unable to. The apparmor package did added a Breaks: media-hub, mediascanner2.0, messaging-app, webbrowser-app because of bug #1756800 and bug #1761176 so I tried upgrades with and without these installed. Test configurations:

* Ubuntu Desktop default install
 * update sources.list to include bionic and run apt-get update
  * apt-get upgrade correctly holds apparmor
  * apt-get dist-upgrade correctly upgrades apparmor
 * revert changes to sources.list and run apt-get update
  * do-release-upgrade -d correctly upgrades apparmor. Package
    removal at end does not suggest removing apparmor. Reboot
    shows apparmor is installed

* Ubuntu Desktop default install with media-hub, mediascanner2.0,
  messaging-app and webbrowser-app installed
 * update sources.list to include bionic and run apt-get update
  * apt-get upgrade correctly holds apparmor
  * apt-get dist-upgrade correctly upgrades apparmor and removes
    media-hub, mediascanner2.0, messaging-app and webbrowser-app
 * revert changes to sources.list and run apt-get update
  * do-release-upgrade -d correctly upgrades apparmor and removes
    media-hub, mediascanner2.0, messaging-app and webbrowser-app.
    Package removal at end does not suggest removing apparmor.
    Reboot shows apparmor is installed

* Ubuntu Server default install
 * update sources.list to include bionic and run apt-get update
  * apt-get upgrade correctly upgrades apparmor (no Breaks
    installed so no reason to hold)
  * apt-get dist-upgrade correctly upgrades apparmor
 * revert changes to sources.list and run apt-get update
  * do-release-upgrade -d correctly upgrades apparmor. Package
    removal at end does not suggest removing apparmor. Reboot
    shows apparmor is installed

* Ubuntu Server default install with media-hub installed
 * update sources.list to include bionic and run apt-get update
  * apt-get upgrade correctly holds apparmor
  * apt-get dist-upgrade correctly upgrades apparmor and removes
    media-hub
 * revert changes to sources.list and run apt-get update
  * do-release-upgrade -d correctly upgrades apparmor and removes
    media-hub. Package removal at end does not suggest removing
    apparmor. Reboot shows apparmor is installed

I believe that the apparmor removal has nothing to do with the new added Breaks in 18.04's apparmor, however, as mentioned, I cannot reproduce.

Can you provide steps to reproduce?

[Jamie Strandboge (jdstrand)]

Looking at https://github.com/lxc/lxd/issues/4504#issuecomment-384759354, it seems that the system may not have had ubuntu-standard installed, so on do-release-upgrade the final package removal step may have listed apparmor.

[Arni Johannesson (webdock)]

Yes the omission of ubuntu-standard seems to be the leading candidate for the cause of this issue. Thank you for investigating.