[Bug 2119012] Re: Ubuntu Studio CD image build failure

[Timo Aaltonen]

Hello Juerg, or anyone else affected,

Accepted lowlatency-kernel into plucky-proposed. The package will build
now and be available at https://launchpad.net/ubuntu/+source/lowlatency-
kernel/1.3~25.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
plucky to verification-done-plucky. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-plucky. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: lowlatency-kernel (Ubuntu Plucky)
       Status: Confirmed => Fix Committed

** Tags added: verification-needed-plucky

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https://bugs.launchpad.net/bugs/2119012

Title:
  Ubuntu Studio CD image build failure

Status in livecd-rootfs package in Ubuntu:
  Confirmed
Status in lowlatency-kernel package in Ubuntu:
  Fix Released
Status in livecd-rootfs source package in Noble:
  Fix Released
Status in lowlatency-kernel source package in Noble:
  Fix Released
Status in livecd-rootfs source package in Plucky:
  Won't Fix
Status in lowlatency-kernel source package in Plucky:
  Fix Committed
Status in livecd-rootfs source package in Questing:
  Confirmed
Status in lowlatency-kernel source package in Questing:
  Fix Released

Bug description:
  [ Impact ]

  Ubuntu Studio uses the lowlatency kernel. With 6.14, the lowlatency
  kernel is just the generic kernel with some bootargs to make it
  lowlatency. This breaks the Ubuntu Studio livefs and CD image builds.

  https://launchpad.net/~ubuntu-
  cdimage/+livefs/ubuntu/noble/ubuntustudio

  Problem 1)

  The postinst hook of the lowlatency-kernel package calls update-grub
  unconditionally which fails if the package is installed in a chroot.

  From a livefs build log:

  Processing triggers for dbus (1.14.10-4ubuntu4.1) ...
  Processing triggers for libgtk-3-0t64:amd64 (3.24.41-4ubuntu1.3) ...
  Processing triggers for shared-mime-info (2.4-4) ...
  Processing triggers for libgtk2.0-0t64:amd64 (2.24.33-4ubuntu1.1) ...
  Processing triggers for desktop-file-utils (0.27-2build1) ...
  Processing triggers for initramfs-tools (0.142ubuntu25.5) ...
  Processing triggers for hicolor-icon-theme (0.17-2) ...
  Processing triggers for libc-bin (2.39-0ubuntu8.5) ...
  Processing triggers for man-db (2.12.0-4build2) ...
  Processing triggers for dictionaries-common (1.29.7) ...
  Processing triggers for linux-image-6.14.0-24-generic (6.14.0-24.24~24.04.3) ...
  /etc/kernel/postinst.d/initramfs-tools:
  update-initramfs: Generating /boot/initrd.img-6.14.0-24-generic
  cryptsetup: ERROR: Couldn't resolve device overlay
  cryptsetup: WARNING: Couldn't determine root device
  cryptsetup: ERROR: Couldn't resolve device /dev/vdb
  Errors were encountered while processing:
   lowlatency-kernel

  Problem 2)

  The kernel flavor name changed from 'lowlatency' to 'generic'. This
  breaks livecd-rootfs.

  [2025-07-30 21:10:37] No catalog entry template for standard.live
  [2025-07-30 21:10:38] P: Begin unmounting filesystems...
  [2025-07-30 21:10:38] P: Saving caches...
  [2025-07-30 21:10:38] No kernel output for lowlatency!
  [2025-07-30 21:10:38] P: Begin unmounting filesystems...
  [2025-07-30 21:10:38] P: Saving caches...
  [2025-07-30 21:10:38] Build failed

  Problem 3)

  The ISO kernel is the generic kernel now so needs additional boot args
  to make it lowlatency. Otherwise 'Try Ubuntu Studio' will run the
  generic kernel which is likely not what we want.

  [ Test Plan ]

  1. Trigger an Ubuntu Studio livefs build and watch it succeed.
  2. Boot a resulting CD image and verify the running kernel is lowlatency.
  3. Install Ubuntu Studio and verify the running kernel is lowlatency.

  [ Where Problems Could Occur ]

  Other consumers of livecd-rootfs could fail, i.e., other livefs builds
  might fail due to livecd-rootfs changes.

  Machines that have the lowlatency-kernel package installed might not
  update grub.cfg and hence not switch the kernel to lowlatency but
  continue to run with generic settings.

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