[Bug 2075969] Re: add support to do-release-upgrade for (EOL) kinetic/lunar to noble upgrades

[Nick Rosbrook]

I will stage these changes in git, but we just did an SRU for the
24.04.2 release, and this is not urgent enough to do another one
immediately.

** Description changed:

+ [Impact]
+ 
+ Users stuck in kinetic, lunar, and mantic cannot upgrade to noble.
+ 
+ [Test Plan]
+ 
+ 1. Perform an upgrade from kinetic
+ 
+ * First, create a jammy container and then manually upgrade it to
+ kinetic:
+ 
+ $ lxc launch ubuntu:jammy j
+ $ lxc exec j bash
+ $ sed -i 's/archive.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list
+ $ sed -i 's/jammy/kinetic/g' /etc/apt/sources.list
+ $ apt update && apt dist-upgrade -y
+ 
+ [...]
+ 
+ * Now, try to upgrade:
+ 
+ $ do-release-upgrade
+ 
+ * This will fail with a message along the lines of "upgrades from
+ kinetic to noble are not supported." Try with the version in -proposed,
+ and it should work now:
+ 
+ $ do-release-upgrade --proposed
+ 
+ * This should run to completion.
+ 
+ 2. Do a jammy -> noble upgrade to ensure no adverse side effects were
+ introduced:
+ 
+ $ lxc launch ubuntu:jammy j
+ $ lxc exec j bash
+ $ do-release-upgrade --proposed
+ 
+ [Where problems could occur]
+ 
+ This patch changes the way From= is used in DistUpgrade.cfg. It now
+ treats that field as a list and interprets it as allowable upgrade
+ paths, instead of requiring a DistUpgrade.cfg.$series to exist for the
+ current series.
+ 
+ This of course could disrupt existing upgrade paths, which is why the
+ test plan requires a jammy->noble upgrade, too.
+ 
+ There were also other places in the code that used that From= field.
+ These have been updated, but if any spots were missed, that could break
+ existing logic.
+ 
+ [Original Description]
+ 
  [Current Behavior]
  Users still on Kinetic and Lunar are prompted to upgrade to Noble via the motd, however d-r-u claims that upgrading from those releases -> noble is unsupported. You also can not upgrade to mantic anymore, so you would need to manually change your sources to facilitate the upgrade.
  
  [Expected Behavior]
  Despite these releases being EOL, historically we have allowed d-r-u (hirsute->jammy for example).
  
  [Replication Steps]
  Launch a lunar instance, upgrade to latest packages, and call do-release upgrade
  
  [Root Cause]
  It appears that we're missing DistUpgrade.cfg.jammy for kinetic/lunar's UpgradeTools . Ideally we should fix this to allow easier upgrades to supported releases, as we had previously.

** Changed in: ubuntu-release-upgrader (Ubuntu Noble)
       Status: Triaged => In Progress

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https://bugs.launchpad.net/bugs/2075969

Title:
  add support to do-release-upgrade for (EOL) kinetic/lunar to noble
  upgrades

Status in ubuntu-release-upgrader package in Ubuntu:
  Fix Committed
Status in ubuntu-release-upgrader source package in Noble:
  In Progress

Bug description:
  [Impact]

  Users stuck in kinetic, lunar, and mantic cannot upgrade to noble.

  [Test Plan]

  1. Perform an upgrade from kinetic

  * First, create a jammy container and then manually upgrade it to
  kinetic:

  $ lxc launch ubuntu:jammy j
  $ lxc exec j bash
  $ sed -i 's/archive.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list
  $ sed -i 's/jammy/kinetic/g' /etc/apt/sources.list
  $ apt update && apt dist-upgrade -y

  [...]

  * Now, try to upgrade:

  $ do-release-upgrade

  * This will fail with a message along the lines of "upgrades from
  kinetic to noble are not supported." Try with the version in
  -proposed, and it should work now:

  $ do-release-upgrade --proposed

  * This should run to completion.

  2. Do a jammy -> noble upgrade to ensure no adverse side effects were
  introduced:

  $ lxc launch ubuntu:jammy j
  $ lxc exec j bash
  $ do-release-upgrade --proposed

  [Where problems could occur]

  This patch changes the way From= is used in DistUpgrade.cfg. It now
  treats that field as a list and interprets it as allowable upgrade
  paths, instead of requiring a DistUpgrade.cfg.$series to exist for the
  current series.

  This of course could disrupt existing upgrade paths, which is why the
  test plan requires a jammy->noble upgrade, too.

  There were also other places in the code that used that From= field.
  These have been updated, but if any spots were missed, that could
  break existing logic.

  [Original Description]

  [Current Behavior]
  Users still on Kinetic and Lunar are prompted to upgrade to Noble via the motd, however d-r-u claims that upgrading from those releases -> noble is unsupported. You also can not upgrade to mantic anymore, so you would need to manually change your sources to facilitate the upgrade.

  [Expected Behavior]
  Despite these releases being EOL, historically we have allowed d-r-u (hirsute->jammy for example).

  [Replication Steps]
  Launch a lunar instance, upgrade to latest packages, and call do-release upgrade

  [Root Cause]
  It appears that we're missing DistUpgrade.cfg.jammy for kinetic/lunar's UpgradeTools . Ideally we should fix this to allow easier upgrades to supported releases, as we had previously.

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