Re: [Xen-users] 3.4-testing : Kernel panic on bootup (mount: couldnotfind filesystem /dev/root/)

["Fajar A. Nugraha" <fajar@xxxxxxxxx>]

On Fri, Aug 28, 2009 at 11:44 AM, Madhu Venugopal
(vmadhu)<vmadhu@xxxxxxxxx> wrote:
>> > I get a feeling that the "mkinitrd" is not doing its job completely.
>> > (or) what am I missing ?
>>
>> My guess is the kernel config you use is missing some essential
>> modules needed to boot correctly. Here's some of the things you can
>> try :
>
> Okay. How would I find what modules are missing ?
> I don't see any such error in the bootup logs. Any other suggestions ?

Start with the boot log. It usually shows you what block devices are
detected, etc.
The basic ones for domU (2.6.18 kernel) are xenblk (domU block device)
and ext3 (or whatever file system you use). For dom0 kernel, it's
easier to see the output of "lsmod" from your working installation.

>
>>
>> - Install RHEL's Xen. This should be pretty straightforward, you'd end
>> up with Xen 3.1+ and a working grub.conf stanza for Xen with RHEL's
>> kernel-xen
>> - Install Xen package from gitco (http://www.gitco.de/repo/). You can
>> get Xen 3.4.1 (currently in testing) but still using RHEL's kernel-xen
>> - If that works, you can simply compile another xen kernel as you
>> like, using either 2.6.18 or later pv_ops kernel. If using 2.6.18, you
>> can use RHEL's kernel-xen config as a base.
>
> I didn't want to take this approach. We have standardized on the
> approach
> to take with the existing XEN installations and kernel to use.

Standard is fine, if it works. What I'm saying is if you want to find
out what's wrong (is it Xen userland? kernel version? kernel config?)
the steps above can help.

> It is
> confusing
> that am the only one seeing this issue while it works just fine on other
> Machines. This makes it clear that it is machine specific and am missing
> Some drivers for them. But am clueless on what is that am missing and
> how
> To include them in initrd. Any suggestions ?

For starters, copy RHEL's kernel-xen config to the kernel from xen.org
(like 
http://bits.xensource.com/oss-xen/release/3.4.0/linux-2.6.18-xen-3.4.0.tar.gz).
That should provide similar set of modules.

Then try running mkinitrd WITHOUT --allow-missing. It should show you
what modules it thinks you should have but currently missing.

-- 
Fajar

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