Fix kernel panic after unattended kernel upgrade#3
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The update-initramfs diversion (to /bin/true) was permanent — applied in bootcmd with no restore. When unattended-upgrades installed a new kernel, its postinst called update-initramfs which silently did nothing. GRUB picked up the new vmlinuz but with no initrd line. On next boot the kernel couldn't load virtio_blk (module in initramfs), so the root disk was invisible and it panicked with "VFS: Unable to mount root fs". Fix: divert only during first-boot provisioning (guarded by boot-finished), then restore in runcmd so future kernel upgrades generate a working initramfs. Add e2e test that installs a second kernel flavor, verifies the initrd is created, reboots, and confirms the VM comes back on the new kernel. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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@ddellacosta I finally had a little time to dig into the kernel panic we both saw. The call was coming from inside the house (overzealous "speed" hack!) |
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@ddellacosta You will probably want to undivert/unsymlink (per the "Undo" bit) your current VM and re-run update-initramfs so you don't lose your work again. |
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Gotcha, will give it a shot! |
The cloud kernel package name includes the arch suffix (linux-image-cloud-arm64 vs linux-image-cloud-amd64). Use dpkg --print-architecture inside the guest to pick the right one. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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The update-initramfs symlink (to /bin/true) made the machine unbootable after updating the kernel (no real surprise there.)
Claude explanation:
When unattended-upgrades installed a new kernel, its postinst called update-initramfs which silently did nothing. GRUB picked up the new vmlinuz but with no initrd line. On next boot the kernel couldn't load virtio_blk (module in initramfs), so the root disk was invisible and it panicked with "VFS: Unable to mount root fs".
Fix: divert only during first-boot provisioning (guarded by boot-finished), then restore in runcmd so future kernel upgrades generate a working initramfs.
Add e2e test that installs a second kernel flavor, verifies the initrd is created, reboots, and confirms the VM comes back on the new kernel.