current ubuntu kernel compression method is breaking VMs using pygrub (Xen)

Christian Ehrhardt christian.ehrhardt at
Wed Jan 26 15:15:51 UTC 2022

On Wed, Jan 26, 2022 at 3:47 PM Oliver Linden <oliver_linden at> wrote:
> With at least the two most recent kernel versions
> linux-image-5.13.0-25-generic
> linux-image-5.13.0-27-generic
> ubuntu switched to ZSTD as default kernel compression method breaking all Xen installations using "pygrub", regardless whether it's a Dom0 or a DomU.
> Please switch back to a "pygrub" supported kernel compression method.

Hi Oliver,
I'm not going into the pygrub side of things here, but I wanted to let
you know that there is [1] which I think reported this issue for xen.
There is work ongoing that tries to get a newer xen into jammy that
can work with that.

There might be SRUs later that fix this in older releases, but given
that xen is "only" in universe I do not want to commit/promise that.


> Best, Oliver
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Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd

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