xen machines not coming up while wrong root device in nova/virt/libvirt.xml.template

[Christian Berendt]

In nova/virt/libvirt.xml.template there is an entry <root>/dev/xvda</root>. I tested starting the ttylinux image on top of Xen and it failed. After changing <root/> do /dev/sda it worked. Also tested with an Ubuntu UEC Image (10.10), also worked fine with /dev/sda.

[Thierry Carrez (ttx)]

That's a default value (you can provide your own template using --libvirt_xml_template) and I suspect the default was chosen for a reason... Maybe XenServer compat ?

[Christian Berendt (berendt)]

---snip---
Using sdX for block devices inside the VM is incorrect. They should be xvdX. This was patched unilaterally by Ubuntu, and then reverted when they realised the mistake they'd made.

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/684875

This has sadly made it into 10.10, but it's not this way in any other version, before or since. If you change this default, you break every other kernel other than Ubuntu 10.10.
---snap---

Workaround is to simple use a modified libvirt template like suggested by Thierry Carrez. I'll close this bug as Invalid.

[Rogério Vinhal Nunes (rogervn)]

I can confirm this bug on updated Ubuntu 10.04.