Re: pygrub??

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Tue, May 26, 2009 at 01:23:29PM +0200, Jean-Yves Migeon wrote:
> joe mcguckin wrote:
> > I finally got Centos running. I had to use pygrub as the bootloader.
> >
> > Why does this make a difference? I can't seem to get it to boot
> > otherwise...
> >
> > Thanks,
> 
> I don't know any specifics about CentOS, but today's Linux kernels are 
> using modules for everything, and it is a nightmare to boot one without 
> modules (or initrd), it always wants to load one sometime or another.
> 
> I guess that with "traditional" domU Xen boot, you do not have the 
> initrd that contains the fs code needed to load the boot device 
> successfully ("ramdisk" option inside the config file).

You could still copy it from the domU's filesystem so that dom0 can
load it

> While with 
> pygrub, it can boot the kernel directly in the image file, and get the 
> ramdisk from there.

Yes, the avantage is that you have your kernel, initrd and modules in
sync. You can do this without pygrub but you have to be carefull to
have modules in your domU's filesystem that matches the domU's kernel
in the dom0 filesystem. If there's a mismatch your domU doesn't boot any
more. I've been in this situation when yum decided to update the domU's
kernel: it removed the older kernels and modules but of course the copy in the
dom0 didn't get updated ...

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--