Latest Focal Minimal disk images from livecd-rootfs do not boot

[Pat Viafore]

[Impact]

 * Minimal images built from livecd-rootfs after March 12th do not boot. There are no broken images on cloud-images.ubuntu.com, but no further images will be published until this is fixed. Cloud-specific minimal images are unaffected, as they do the proper steps in their build hooks to mitigate this problem.

[Test Plan]

 * Build a minimal image from livecd-rootfs in the focal branch.
 * Launch it through qemu to verify it boots: qemu-system-x86_64 -cpu host -machine type=q35,accel=kvm -m 2048 -snapshot -netdev id=net00,type=user,hostfwd=tcp::2222-:22 -device virtio-net-pci,netdev=net00 -drive if=virtio,format=qcow2,file=focal-server-cloudimg-amd64.img -drive if=virtio,format=raw,file=seed.img -nographic
 * Verify cloud-specific minimal builds still operate as intended (single boot, no double boot fallback)

[Where problems could occur]

 * The changes are forcing a boot without initramfs for all minimal images. This was the default behavior before the March 12th change.

[Bug Description]

Here is the kernel panic:

VFS: Cannot open root device "LABEL=cloudimg-rootfs" or unknown-block(0,0): error -6
Please append a correct "root=" boot option; here are the available partitions:
fe00 2306048 vda
 driver: virtio_blk
  fe01 2192367 vda1 eba1d37a-4dc1-4c42-8cab-ed045e561faa

  fe0e 4096 vda14 9bbe6566-13bd-412a-9a58-8d85918ebe0f

  fe0f 108544 vda15 b4d6d9b6-0a70-41eb-9d71-5d64fc7e7d08

fe10 366 vdb
 driver: virtio_blk
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-1034-kvm #35-Ubuntu
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-1 04/01/2014
Call Trace:
 0xffffffff92b471a8
 0xffffffff92b23a3d
 0xffffffff9332f5d4
 0xffffffff9332f6b0
 0xffffffff9332f7e7
 0xffffffff9332f287
 ? 0xffffffff92b4a5e0
 0xffffffff92b4a5e9
 0xffffffff92c00215
Kernel Offset: 0x11400000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ]---

Kernel command line :

Linux version 5.4.0-1034-kvm (buildd@lgw01-amd64-033) (gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04)) #35-Ubuntu SMP Wed Feb 24 14:09:38 UTC )
Command line: BOOT_IMAGE=/boot/vmlinuz-5.4.0-1034-kvm root=LABEL=cloudimg-rootfs ro console=tty1 console=ttyS0

The root should be set to a PARTUUID, not a label.

[Pat Viafore (patviafore)]

Commit 4c504f678178104eceaf5b3aae40bcff20863235 needs to be backported to Focal to fix this

[Brian Murray (brian-murray)]

Is this fixed in the development release of Ubuntu (hirsute)?

[Robert C Jennings (rcj)]

This is fixed in devel in changes that span multiple commits and this bit was omitted from the backport of those changes (which broke focal images)

[Brian Murray (brian-murray)]

Hello Pat, or anyone else affected,

Accepted livecd-rootfs into focal-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/livecd-rootfs/2.664.19 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-focal to verification-done-focal. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-focal. 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.

[Pat Viafore (patviafore)]

I have done testing on minimal images built from 2.664.19 livecd-rootfs and run them through qemu to verify they still boot. I have also tested cloud-specific images to make sure they do not double boot as part of this change.

[Launchpad Janitor (janitor)]

This bug was fixed in the package livecd-rootfs - 2.664.19

---------------
livecd-rootfs (2.664.19) focal; urgency=medium

  [ Patrick Viafore ]
  * Fix broken minimal cloud image boot on amd64 LP: #1920043

 -- Robert C Jennings <email address hidden> Mon, 22 Mar 2021 10:57:50 -0500

[Brian Murray (brian-murray)]

The verification of the Stable Release Update for livecd-rootfs has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.