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[Xen-users] RE: DomU boot fails with can't find root on Fedora 6

To: "Ligesh" <myself@xxxxxxxxxx>
Subject: [Xen-users] RE: DomU boot fails with can't find root on Fedora 6
From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
Date: Wed, 31 Jan 2007 16:02:58 +0100
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Thread-topic: DomU boot fails with can't find root on Fedora 6
 

> -----Original Message-----
> From: Ligesh [mailto:myself@xxxxxxxxxx] 
> Sent: 31 January 2007 14:53
> To: Petersson, Mats
> Cc: Xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: DomU boot fails with can't find root on Fedora 6
> 
> On Wed, Jan 31, 2007 at 03:36:54PM +0100, Petersson, Mats wrote:
> >  
> > 
> > > -----Original Message-----
> > > From: Ligesh [mailto:myself@xxxxxxxxxx] 
> > > Sent: 31 January 2007 14:26
> > > To: Petersson, Mats
> > > Cc: Xen-users@xxxxxxxxxxxxxxxxxxx
> > > Subject: Re: DomU boot fails with can't find root on Fedora 6
> > > 
> > > 
> > >  Hi Pete,
> > > 
> > >  Do we need separate initrd for each ostemplate? In the stock 
> > > kernel I got from xensource on centos 4.4, I was able to boot 
> > > all domUs using the same initrd, and I had thought that that 
> > > was the standard way. This is a big hassle actually, that for 
> > > each domU distro, you have to use different initrd images.
> > 
> > Don't know who "Pete" is, but... 
> 
>  I do have an issue with names. It should have been Mats. I 
> guess, in my head your name was pete mattersson, since peter 
> is a more common first name. :-) 
> 
> > 
> > Of course, DomU is a pretty well-defined environment - 
> unless you expose
> > some hardware through the PCI hide/pass settings, your DomU 
> will never
> > see any real hardware, so you don't REALLY need a modular 
> kernel, one
> > with builtin drivers should be fine. That way you can eliminate the
> > initrd modules altogether, since all drivers are included 
> in the kernel.
> > Obviously, Dom0 kernel has to cope with different types of 
> SCSI, IDE,
> > SATA, SAS, RAID controllers, network cards from different 
> manufacturers,
> > etc, etc. So building a kernel with all drivers included 
> would make a
> > pretty large kernel, and using modules here makes sense to 
> save memory
> > (since memory is only used by modules actually loaded). 
> > 
> 
>  But it seems the fedora people have build the kernel without 
> the xen drivers. As in, if you don't use initrd, then it will 
> fail miserably by saying unrecognized device '/dev/vbd/2567', 
> which is the xen harddisk. They have compiled the xen drivers 
> as modules, and I read in some mailing list post that it was 
> because it was absolutely necessary for anaconda to work or 
> something. SO I guess, fedora is a dying distro and it is 
> best to keep away from it. I am not really seeing any really 
> enthuisiastic documentation on different aspects of 
> virtualization, and mailing list conversation are also pretty 
> much vague and lack any real information content--mostly 
> people making guesswork.

You could try adding "--omit-lvm-modules" to your mkinitrd line - that
should make it not include any of the LVM stuff that would be part of
your initrd when building on a LVM-based system. [I found that by "cat
/sbin/mkinitrd|grep -i lvm", I haven't tried it, so it IS guess-work - I
don't use LVM, so it would take me longer to set that up and make it
work than it would take you to build a new initrd and try it, I'm pretty
sure]. 

I'm not going to guess (speculate) on what Fedora are doing, or why they
build it the way they do, etc, etc. 

> 
>  So finally, I think I will have to build custom kernel for 
> fedora 6, which actually defeats the entire purpose of 
> distro-built-in-with-xen.

I guess(!) you got a point there. 

--
Mats
> 
>  Thanks.
> 
> 
> 
> 
> 
> 
> 



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