[Bug 1988299] Re: Can't upgrade from 20.04 to 22.04 due to extreme space requirement for /boot

[George]

I had the same issue. I managed to work around it by removing all but
the running kernel version (5.15.0-46) and changing the initramfs
compression setting to 'lzma'.

The issue seems to result from lines 1146, 1148 of
DistUpgrade/DistUpgradeCache.py:

1146    if pkg.marked_install or pkg.marked_upgrade:
1148        kernel_count += 1

The package for my running kernel (5.15.0-46) was marked for upgrade to
the jammy version of the same kernel. As far as I know, this package
upgrade would not result in an *additional* kernel image and initrd
image being generated, so incrementing kernel_count erroneously
increases /boot space requirements.

However, there is justification on lines 1144, 1145 for the above code
snippet:

1144    # upgrade because early in the release cycle the major version
1145    # may be the same or they might be -lts- kernels

so I am not sure if this behavour of the upgrade tool should be
considered a bug.

It seems like the boot-performance-motivated switch to lz4 for initramfs
compression may have left those with separate /boot partitions in a
situation where Ubuntu's default initramfs.config is inappropriate.
Ultimately, this seems to be an Ubuntu UX issue caused by inappropriate
default configs generated at install-time. So it may make sense to close
this issue as a wontfix, and open a new issue for the installer
regarding its selection of initramfs compression settings in the case
where a separate /boot partition is used.

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https://bugs.launchpad.net/bugs/1988299

Title:
  Can't upgrade from 20.04 to 22.04 due to extreme space requirement for
  /boot

Status in ubuntu-release-upgrader package in Ubuntu:
  Incomplete

Bug description:
  I'm attempting to upgrade from 20.04 to 22.04 and my installation uses
  full disk encryption, so I have a separate partition for /boot.

  The size of the /boot partition was set by the installer for 20.04 (to
  704 MiB) and I currently have 329 MiB free after removing old kernels
  with apt autoremove:

    $ df -h /boot
    Filesystem      Size  Used Avail Use% Mounted on
    /dev/sdb2       704M  324M  329M  50% /boot

  When attempting to upgrade to 22.04 it fails with:

    The upgrade has aborted. The upgrade needs a total of 787 M free
    space on disk '/boot'. Please free at least an additional 442 M of
    disk space on '/boot'. You can remove old kernels using 'sudo apt
    autoremove' and you could also set COMPRESS=xz in
    /etc/initramfs-tools/initramfs.conf to reduce the size of your
    initramfs.

  So it claims to need more space than the total size of the partition
  (so presumably no amount of compressing initramfs will be enough!),
  which as noted above is the default size for /boot chosen by the 20.04
  installer.

  Another instance of this issue has been raised here: https://askubuntu.com/q/1423156/57751
  --- 
  ProblemType: Bug
  ApportVersion: 2.20.11-0ubuntu27.24
  Architecture: amd64
  CasperMD5CheckResult: skip
  CrashDB: ubuntu
  CurrentDesktop: ubuntu:GNOME
  DistroRelease: Ubuntu 20.04
  InstallationDate: Installed on 2020-04-25 (859 days ago)
  InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
  NonfreeKernelModules: nvidia_modeset nvidia
  Package: ubuntu-release-upgrader (not installed)
  ProcVersionSignature: Ubuntu 5.15.0-46.49~20.04.1-generic 5.15.39
  Tags:  focal dist-upgrade
  Uname: Linux 5.15.0-46-generic x86_64
  UpgradeStatus: Upgraded to focal on 2022-08-31 (1 days ago)
  UserGroups: adm cdrom dip docker lpadmin lxd plugdev sambashare sudo
  _MarkForUpload: True

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