Re: [Xen-users] Boot Problem with XEN 3.1.

Tim Post
Sun, 16 Sep 2007 02:24:14 -0000

On Sat, 2007-09-15 at 23:12 +0200, Paradox wrote:
> Hi to all.
>
> I''m installed XEN3.1 correctly but I''m some problem to
start it. XEN
> start but I received this message:
>
> VFS: Cannot open root device "hda5" or unknown-block(0,0)
> Please append a correct "root=" boot option
> Kernel panic - not syncing: VFS: Unable to mount root fs on
> unknown-block(0,0)
>
> This is strange because my grub is configured like this:
>
> #XEN3.1-2.6.18
>   title XEN3.1-2.6.18
>   #root (hd0,4)
>   kernel (hd0,4)/boot/xen-3.1.gz dom0_mem=262144
>   module (hd0,4)/boot/vmlinuz-2.6-xen root=/dev/hda5 ro console=tty0

Do you need an initrd? It looks like your kernel is not able to access
whatever type of disk /dev/hda5 is.

I use the following modules on my machine when making the initrd,
booting to IDE drives as well:

ide-cd
ide-disk
ide-generic
libata
ext3
jfs

This lets me access all of the partitions that I need to continue
booting, at which point I pick up device mapper modules and LVM. Likely,
you don''t need jfs.

> I say "strange" because I have a slack partition (is logical
partition)
> that start well and is configured like this:
>
>   title Slack-2.6.21.5
>   root (hd0,4)
>   kernel (hd0,4)/boot/vmlinuz-huge-2.6.21.5 root=/dev/hda5 ro vga=773

Yes, this is strange. The only explanation is the kernels being built a
little differently. Likely, your 2.6.21.5 kernel has the modules listed
above (or whatever modules are needed to boot) built in, not needing the
modules or initrd any longer.

> XEN kernel is installed under this slack partition, so root option is
> correctly.
>
> You can help me?

Hope so :) You can try a menuconfig on your Xen kernel and build the
generic IDE stuff without modular support, or try an initrd.

I''m quite happy with the performance of the generic IDE drivers. If you
have a special chip set or controller, you might want to find better
drivers. The above should get you booting at least.

Hope this helps :)

--Tim