Cant Boot Ubuntu 22.04 LTS after release update

Meth0d

Coming from 20.04 LTS i updated my VM to 22.04 LTS and now i cant start it anymore:

vm.start
{
  "id": "9a540088-556f-30ba-434f-317697ca6532",
  "bypassMacAddressesCheck": false,
  "force": false
}
{
  "code": "INTERNAL_ERROR",
  "params": [
    "xenopsd internal error: (Failure
  \"Error from xenguesthelper: xenguest: xc_dom_parse_image: [2] panic: xc_dom_core.c:693: xc_dom_find_loader: no loader found\")"
  ],
  "call": {
    "method": "VM.start",
    "params": [
      "OpaqueRef:c817057a-3994-4447-8ed1-8322610029c9",
      false,
      false
    ]
  },
  "message": "INTERNAL_ERROR(xenopsd internal error: (Failure
  \"Error from xenguesthelper: xenguest: xc_dom_parse_image: [2] panic: xc_dom_core.c:693: xc_dom_find_loader: no loader found\"))",
  "name": "XapiError",
  "stack": "XapiError: INTERNAL_ERROR(xenopsd internal error: (Failure
  \"Error from xenguesthelper: xenguest: xc_dom_parse_image: [2] panic: xc_dom_core.c:693: xc_dom_find_loader: no loader found\"))
    at Function.wrap (/opt/xen-orchestra/packages/xen-api/src/_XapiError.js:16:12)
    at /opt/xen-orchestra/packages/xen-api/src/transports/json-rpc.js:35:21
    at runNextTicks (node:internal/process/task_queues:60:5)
    at processImmediate (node:internal/timers:447:9)
    at process.callbackTrampoline (node:internal/async_hooks:130:17)"
}

Maybe because this VM was created as 18.04 some years ago? How can i fix that

stormi

Was your VM installed as a PV guest instead of HVM?

Meth0d

@stormi Yes its a PV VM

stormi

Then there are probably extra steps to do when the bootloader changes like probably happened in this upgrade.

I'm not familiar with the steps myself, PV guests being not supported since XCP-ng 8.1 and only kept (for now) for compatibility with very old VMs.

Why was this ubuntu installed as a PV guest in the first place?

Meth0d

I am not sure why exactly, probably because the inital Install is quite old, i think its coming from 14.04. or 16. I will try to install grub on xvda and convert it. I was not aware that PV would become "suddenly" an issue

olivierlambert

You should really leave PV as soon as possible, in terms of performance and security, HVM is better.

Meth0d

I converted to PVHVM after using grub-install /dev/xvda successfully on Ubuntu 20.04 LTS and it boots just fine.

Now if i do-release-upgrade to 22.04 LTS the VM hangs on GRUB "grub_disk_native_sectors".
Am i missing something ?

olivierlambert

Hmm that's weird. You could try to use a LiveCD to do a grub install (in a chroot) or use Grub rescue CD and force a rewrite of Grub.

To me, it's a pure Grub issue in this case.

Meth0d

As this is just a test restore of my live system i have a snapshot pre-release upgrade. Can i do something else besides using grub-install and update-grub ? I have found this while looking for the error: https://askubuntu.com/questions/1404066/executing-grub2-command-nativedisk-before-boot-for-huge-disks

But to me its unclear why its should be necessary to mess with the disk module all of a sudden.

olivierlambert

I have no idea either. Probably a question to the Ubuntu I think, because I can't see any reason why it could be connected to HVM mode (which is close to the "metal" in terms of Grub behavior!)

Meth0d

@olivierlambert after fiddeling around with almost every advice including dpkg-reconfigure grub-pc and to re-enable OS Proper (which aparently was disabled between 20.04 and 22.04) the one thing that worked for me was to purge grub* and reinstall it.

So i still have no idear what was going on, but i have my VM booting now on 22.04
Thanks for all the idears.

olivierlambert

Great news Happy using HVM mode with a "free" 20/30% boost

andrewperry

@Meth0d thanks for sharing your experience. Fortunately I was able to just hit "Convert to HVM" after my imported PV failed to reboot after upgrade from 20.04 to 22.04 - was all set to load a livecd etc too!