Re: [Xen-devel] Xen 4.x / Linux 3.x (dom0 and HVM domU) and NIC handling

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2011-12-02 at 17:16 +0000, Alex Bligh wrote:
> 
> --On 2 December 2011 16:40:48 +0000 Ian Campbell <Ian.Campbell@xxxxxxxxxx> 
> wrote:
> 
> >> AFAIK changing xen_platform_pci=0|1 will switch rather more than just
> >> the NIC. It will switch your disk too, instantly causing your previously
> >> happily booting OS to fail to boot as the root device name changes.
> >
> > We recommend you use "root=LABEL=foo" rather than "root=/dev/blah" for
> > this reason. Fortunately most distros use that scheme by default these
> > days.
> 
> Yes; and /etc/fstab. UUID= works too.

Right.

> FWIW my experience is that various built-for-cloud type distros don't use
> that scheme, mainly because they use grub1 which IIRC does not support
> this, and building images in a non-root environment that have grub1
> in is rather easier than grub2.

UUID= and LABEL= are functions of your initrd (actually udev) and not
the bootloader. They work with both grub1 and grub2.

> So, for instance, all the vm-builder stuff in debian/ubuntu used grub1
> and did not work this way.

Which ones are these?

The Debian installer uses UUID where it can AFAIK. Ubuntu's installer is
derived from Debian's so I'd expect it to be the same.

> However, my point was that xen_platform_pci does not only change
> whether your net driver is emulated or PVHVM, but also whether your
> disk, and indeed everything else is emulated or PVHVM.

That is indeed worth highlighting.

Ian.




_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel