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Re: [Xen-users] Kernel panics

  • To: xen-users@xxxxxxxxxxxxxxxxxxx
  • From: Yves Dorfsman <yves@xxxxxxxxx>
  • Date: Thu, 05 Jul 2007 06:20:47 -0600 (MDT)
  • Delivery-date: Thu, 05 Jul 2007 05:18:49 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>

On Thu, 5 Jul 2007, Martin Goldstone wrote:

"Please append a correct "root=" boot option"
"Not syncying VFS unable to mount root fs on unknown-block(2,0)"
(sort of, I'm catching this just before it reboots !).

I'm assuming you've already got a root= entry, but I've noticed
sometimes that what works as the root= under a regular kernel doesn't

I have used the same as for my regular kernel:

under Xen (I've noticed this mainly on RHEL systems, they have a
tendency to use root=LABEL=/, and under certain Xen kernels (though not
on the 2.6.18 that comes with the Xen 3.1 binary) I've had to point it
to the correct device (though to be fair, it could have been my initrd).

Do you HAVE to have an initrd, or if you managed to put all the
necessary drivers in the kernel, you should be able to boot without an
initrd ?

As long as you have all the driver's needed to boot the kernel, you
should be fine without an initrd

Thanks, that's what I thought, so I'll stop wasting my time with initrd for now, and concentrate on the kernel panic itself.

My root partition is formated with JFS. Can this be an issue, or as long
as I have the JFS drivers in the kernel I should be fine ?

Again, as long as you have you have either the driver in the kernel or
the module in the initrd, this should be fine.  I've not come across any

Thanks, that's what I through.

Or a way to make it stop and wait for a key to be pressed before it
reboots ?

I add noreboot to the end of the dom0 kernel's module line in grub (not
the kernel line, as that's Xen, but usually the line below it.


When I do use an initrd, I get a segfault from the linuxrc.
Depending what version of mkinitrd I use I get different results, a lot
of the time I can't even mount the gunzip resulting file, and when I can
mount it, I get a lot of empty directories.... Is there a better way of
producing the initrd ?

I always use mkinitrd, and I've not had a problem like this before.
What distro are you using?


Do you put anything weird in your initrd?

I let mkinitrd do its stuff. What do you mean by that ?

Are you using the stock binaries from the Xen site, or are you rolling
your own?

For xen.gz, I 've tried both.
For the kernel, I had to build my own, as there is no driver nor module in the "dist" one.

Is mkinitrd returning any errors?


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