[Bug 2039268] Re: When upgrading to Mantic, it fails to install snap firmware-updater

[Haw Loeung]

** Also affects: ubuntu-release-upgrader (Ubuntu Noble)
   Importance: High
       Status: Invalid

** Also affects: snapd (Ubuntu Noble)
   Importance: Undecided
       Status: Fix Committed

** No longer affects: ubuntu-release-upgrader (Ubuntu Noble)

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https://bugs.launchpad.net/bugs/2039268

Title:
  When upgrading to Mantic, it fails to install snap firmware-updater

Status in snapd package in Ubuntu:
  Fix Committed
Status in ubuntu-release-upgrader package in Ubuntu:
  Invalid
Status in snapd source package in Lunar:
  Fix Released
Status in snapd source package in Mantic:
  Fix Released
Status in snapd source package in Noble:
  Fix Committed

Bug description:
  [Impact]

  While upgrading to Mantic the following message is reported:

  installing snap firmware-updater
  error: cannot perform the following tasks:
  - Automatically connect eligible plugs and slots of snap "firmware-updater" (internal error: auto-connect of &{"firmware-updater:desktop-legacy" "snapd:desktop-legacy"} failed: snap "snapd" has no slot named "desktop-legacy")

  
  [Test case]

  Confirming the failure:

  $ lxc launch ubuntu:lunar lp-2039268
  Creating lp-2039268
  Starting lp-2039268
  $ lxc exec lp-2039268 bash
  # sed -i -e's/lunar/mantic/' /etc/apt/sources.list && apt update && apt install -y systemd
  # ls -l /run/systemd/generator/snap.mount
  -rw-r--r-- 1 root root 274 Oct 18 05:49 /run/systemd/generator/snap.mount
  # ^D
  $ lxc delete --force lp-2039268

  Confirming the fix:

  $ lxc launch ubuntu:lunar lp-2039268
  Creating lp-2039268
  Starting lp-2039268
  $ lxc exec lp-2039268 bash
  # sed -i -e's/lunar/mantic/' /etc/apt/sources.list && apt update && apt install -y systemd
  # ls -l /run/systemd/generator/snap.mount
  ls: cannot access '/run/systemd/generator/snap.mount': No such file or directory
  # ^D
  $ lxc delete --force lp-2039268

  [Where problems could occur]
  This fix changes how snapd detects at boot time whether a bind remount of /snap with different mount options is necessary.  In unusual circumstances where the rootfs mount options are not what we expect by default in Ubuntu, AND the systemd generator is blocked by a custom security policy from reading /proc/1/mounts, it would get the wrong answer, fail to generate the mount unit under necessary circumstances, and regress the behavior of snapd.

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