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Windows Server 2022 HyperV / Ubuntu 20.04 and 22.04 / Processor compatibility mode/ "can't allocate initrd"

pw flag

When running Ubuntu 20.04 or 22.04 on Windows Server 2022 HyperV with Processor compatibility mode^1 enabled the Gen v2 VM won't boot and stops with "can't allocate initrd"^2 error.

Even the normal generic kernel don't work. Using a Gen v1 VM works fine.

Without enable Processor compatibility mode you can't do live migration to different servers. So this blocks me from upgrading my Windows 2019 servers to Windows 2022 servers.

This happens on a System with a AMD Ryzen 5 3600 but not on a AMD Ryzen 7 5700G.

The kernel panic is:

VFS: Cannot open root device "(null)" or unknow-block(0,0): error -6

Tried now from grub cmd. Reproduced via ubuntu server live cd ubuntu-20.04.4-live-server-amd64.iso Secure boot is disabled.

> set root=(cd0)
> linux /casper/vmlinux
> initrd /casper/initrd
error: can't allocate initrd
David avatar
cn flag
From your question. So this blocks me from upgrading my 2019 servers to 2022 What does this mean are these versions of something?
Michael Kriese avatar
pw flag
Updated. It's blocking Windows Server Upgrade.
Michael Kriese avatar
pw flag
I'm able to see the kernel panic, screenshot: https://techcommunity.microsoft.com/t5/image/serverpage/image-id/456912iE4B5951E3B8236E3/image-dimensions/2500?v=v2&px=-1
David avatar
cn flag
Have you tried to upgrade the Windows server before loading the Ubuntu stuff?
Michael Kriese avatar
pw flag
No, this server was freshly installed with windows server 2022. It has all available updates installed.
Michael Kriese avatar
pw flag
This hapens when booting the default command from `ubuntu-20.04.4-live-server-amd64.iso`
Michael Kriese avatar
pw flag
Tried now from grub cmd ```console set root=(cd0)
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