grub2 + xen + lz4 kernels

[Shaun Reitan]

I currently use XEN to boot PV (paravirt) virtual server instances for our customers. Grub2 introduced support for booting a xen kernel directly from a guests disk image which has worked great for years. We use the following command to build our image

grub-mkstandalone -O x86_64-xen -o grub2-x86_64.gz boot/grub/grub.cfg

What we have been seeing more and more is newer distros like Ubuntu 20.04 using lz4 compressed kernel images which will not boot and displays the error "not xen image."

If i use the https://raw.githubusercontent.com/torvalds/linux/master/scripts/extract-vmlinux utility to decompress the kernel image I am able to boot it without any issues using our current grub2 xen loader.

My question is how can I get lz4 support added into grub2 for xen? We are willing to pay for a dev to add this support if needed as I have limited time to really dig into this.

There are a few workarounds out their, most involve a hook that decompresses the kernel after an update but I'm not wanting to add complexity to the kernel update process. It leaves too much room for error and the possibility of a clients server failing to boot after what should of been a simple kernel upgrade.

Any help, even if just pointing me in the right direction would be appreciated!

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Shaun Reitan

NDCHost.com