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I'm trying to migrate various services from a physical Debian Squeeze box to a number of para-virtualised Xen machines. This is my first venture into Xen, so I'm planning on doing this step by step:

  1. Install a clean Xen + Debian Squeeze Dom0 on to the box
  2. Make sure I can install and run new DomUs (xen-tools)
  3. Convert to original physical install (called Kowalski) to a DomU
  4. Move services from Kowalski to new DomUs, until Kowalski isn't doing anything anymore.
  5. Retire Kowalski

Steps 1 and 2 have gone fine. I'm having trouble on 3.

Basically I've:

  • Copied the old Physical partitions to LVM logical volumes
  • Created a kowalski.cfg for Xen that maps these LVs to xvda devices
  • Edited the fstab to use the xvda devices.

It boots, but during the start-up scripts eventually hangs with init reporting that 'T0' is respawning to quickly so it's killing it.

Any suggestions on debug techniques? what I might have missed?

As I say, this is my first venture into Xen and I'm finding it difficult to get a handle on whats going wrong.

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2 Answers 2

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That`s what I initially did (convert p2v). This is a troublesome way to do it.

Better install a fresh, clean DomU with a PV kernel right from the start and then migrate the services to that box.

It is basically the same task as a pyhsical upgrade - but will get you a stable machine faster then the other way round.

I tried to emulate "/dev/sda" for years in my DomUs - just to find that after a certain sles-kernel-update the DomUs did not boot any longer (because sda was now hardcoded to use physical drivers). Now I use the standard-pv-driver (xenblk) with the standard device name (xvda) and everything is fine again.

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I'm starting to agree with you. I was hopeful that I could save myself down time whilst I got the new VMs running. –  Paul S Nov 27 '11 at 10:21
    
Creating new DomUs from scratch is the faster way - believe me. It took me some hours with every new DomU OS linux system to get rid of the old physical drivers for the disk (I learned a lot on that way - but if I look back - I would not do it again). –  Nils Nov 27 '11 at 20:08

You can't just move physical hdd to virtual machine. Squeeze uses 2.6.32 kernel, that can't boot under xen pv (are you using PV?). You need install xen specific kernel linux-image-2.6.32-5-xen-amd64 in virtual machine that can boot under xen. actually you can mount your lvm, chroot in it and install new kernel, and try to start it again. it should work.

also there is some software that can convert physical machines to xen. unforunately i've never used it and i don't remember its name.

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Yep, I'm PV. I'll double check the kernel, but I'm pretty sure it's already Xen'd as I presumably wouldn't get as far as the init scripts if it wasn't. –  Paul S Nov 27 '11 at 10:18

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