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I've got a new Fedora box that I'm setting up as a Xen host (Dom0), which is proving a little more difficult than expected.

First stop - install Xen via DNF and reboot. Find that the Xen boot option fails (lots of errors about multiboot). After a bit of googling I learn that this is because multiboot has been stripped out due to security concerns.[1]

Ok - well that's annoying. Looks like I have two options [2]:

  • Manually reconfigure GRUB to use the older Chain Loader behaviour
  • Bypass GRUB and use Xen as the EFI bootloader

I'm going for option 2, since this seems like a cleaner solution and doesn't require wrangling the layers of shell scripts that have built up around GRUB these days to make it do what I want.

I've gotten as far as creating an EFI boot option for Xen, but it appears to get silently skipped on start up. No errors, no useful output. I'm not sure what to check next.

What I've got so far:

EFI partition has EFI/xen with:

  • xen.efi (copy of EFI/fedora/xen-4.11.1.efi)
  • Copies of initramfs & vmlinuz from /boot
  • xen.cfg

xen.cfg text:

[global]
default=fedora

[fedora]
options=
kernel=vmlinuz root=/dev/nvme0n1p1 rhgb LANG=en_GB.UTF-8
ramdisk=initramfs.img

EFI option created using:

efibootmgr -c -L Xen -d /dev/sdc -p 1 -l \\EFI\\xen\\xen.efi -c

Target state here is: Machine booting with Xen and a Fedora Dom0. What should I check, or what should I try next?

[1] https://access.redhat.com/security/cve/cve-2015-5281

[2] https://wiki.xenproject.org/wiki/Xen_EFI

  • Just curious: why Xen and not KVM? – mattdm Dec 29 '18 at 17:31
  • I'm planning to go with paravirtualized VMs (no need to emulate any kind of hardware, so closer to the metal and a little more efficient). – Adam Luchjenbroers Dec 29 '18 at 22:37
  • I'm not sure that's an up-to-date assessment. See this from 2015, even. – mattdm Dec 30 '18 at 4:00
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Ok, so as it turns out my efibootmgr command was correct (must've been a typo the first time I typed it).

That got me as far as booting the kernel, but the stock Fedora kernel kept suffering from a kernel oops at start-up (which was resolved via a kernel update).

And the Xen Dom0 is then up and running.

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