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Specifically, Citrix XenServer 5.6.

I can map the an ISO from a Storage Repository with no issues and mount it inside the OS but I can't boot from the DVD drive without converting it to HVM, which causes problems because the ISO I'm trying to boot from is a "Bare Metal" restore so it's a tad bit sensitive to whether it boots into paravirt or HVM mode (for example, former uses paravirt drivers for primary HDD at /dev/xvda whereas the latter puts primary HDD at /dev/sda).

I've looked online and the only thing I've been able to find are instructions on how to boot from ISO by converting to HVM (which works for the boot, but undercuts the reason for the boot in the first place).

I've looked around without much luck on how to configure Citrix's PyGrub to boot from ISO. No joy on that, and the only PyGrub examples I've found don't look like they're going to play well with Citrix and are far too manual for that to be our SOP in case of disaster recovery.

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  • Is the Citrix XENServer able to PXE-boot a PV DomU? Apart from that - what is your base problem which you are trying to fix with this? If I have boot-problems with a Xen-PV-DomU I mount it in the Dom0, fix it there and everything is fine. Please add details about your DomU-OS, too. – Nils Sep 4 '13 at 20:21
  • The base problem is that I'm attempting a "Bare Metal" restore of a VM, but to do so, I must boot from the Backup Software's ISO. Changing the from paravirt to HVM lets me boot from an ISO but HVM presents the device names differently so the actual Restoration says it finishes but in actuality fails because the device names get screwed up. Hence why I'm looking for something that lets me boot from ISO in paravirt mode. – Bratchley Sep 5 '13 at 15:09
  • This PXE boot in Citrix does not sound too good - so it seems impossible to PXE-boot a PV. You need something like Grub4DOS that can be started by pygrub... – Nils Sep 5 '13 at 21:01
  • No way around that bare-metal? Can't you just restore the last full backup to another location? – Nils Sep 6 '13 at 13:44
  • I'm currently testing your process, I'm just trying different permutations, it may work and be "auto-pilot" enough to become our policy. But no, we need bare metal in the event of disaster recovery or a production VM become inoperable for any reason. – Bratchley Sep 6 '13 at 13:52
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I can give you the outline of an idea that could work.

This link describes a Grub2 ISO-Boot for Ubuntu. IMHO it does not matter which Linux this is - so it should work on all distributions.

Now the plan:

  1. Create a minimal running PV-linux on xvda, install grub2 there
  2. Create xvdb and place your iso-image there (just as plain file)
  3. Create a boot-entry within that PV-DomU to boot the iso
  4. Boot the DomU
  5. Restore into xvda
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