Re: [Xen-users] VFS: Unable to mount root fs on unknown-block(0,0)

[Bo <barnesno@xxxxxxxxx>]

Tim Post wrote:
> On Sat, 2006-12-16 at 15:35 -0500, Bo wrote:
>   
>> I have compiled a kernel from the sources in xen-3.0.3_0-src.tgz.  I
>> generated an initrd via mkinitrd /boot/initrd-2.6.16.29-xen.img
>> 2.6.16.29-xen (after doing a depmod) 
>>
>> I did a make world/make install from the source directory, per
>> instructions in the README.  I extracted the files from the initrd file
>> to see what the init script looked like.  It has a line inserting the
>> ext3.ko module.
>>
>> The last few lines from the output:
>>
>> (XEN) Xen trace buffers: disabled
>> (XEN) Xen is relinquishing VGA console.
>> (XEN) *** Serial input -> DOM0 (type 'CTRL-a' three times to switch
>> input to Xen).
>> Kernel panic - not syncing: VFS: Unable to mount root fs on
>> unknown-block(0,0)
>>  (XEN) Domain 0 crashed: 'noreboot' set - not rebooting.
>>
>>     
>
> Bo, is it possible (with your hardware) to boot without an initrd? I'd
> look at the initrd itself. 
>
> You notice unknown-block(0,0), when its obvious that you passed the
> correct root as a kernel paramater, which is correct at 1,1.
>
> My *guess*, and this is only a guess is that you could try swapping the
> order of ro and root= in your boot config. I don't work much with
> Fedora, however it looks like "ro" is being passed as the real_root_fs,
> and a default value of 0,0 is being passed to pivot root because
> obviously no block device named 'ro' exists.
>
> In other words, the order of the arguments could be an issue. Your
> initrd is "dumb". 
>
> I'd try switching them, then try booting without the initrd. The chain
> loading process of pivoting to the real root FS is broken in between
> vmlinuz and your initrd. 
>
> This should not be an issue, but doesn't mean it isn't an issue :)
>
> Again, just a guess but a simple one to try.
>
> Hope this helps -
> Best,
> -Tim
>
>
>
>
>   
Using this:
root (hd1,1)                                                           
kernel /boot/xen.gz dom0_mem=262144 noreboot com1=19200n81             
module /boot/vmlinuz-2.6.16-xen root=/dev/hdb2 ro quiet console=tty0 > 
 module /boot/initrd-2.6.16.29-xen.img


I get :
Red Hat nash version 4.2.15 starting
mount: error 6 mounting ext3
ERROR opening /dev/console!!!!: 2
error dup2'ing fd of 0 to 0
error dup2'ing fd of 0 to 1
error dup2'ing fd of 0 to 2
switchroot: mount failed: 22
Kernel panic - not syncing: Attempted to kill init!
 (XEN) Domain 0 crashed: 'noreboot' set - not rebooting.

Removing the initrd line results in the exact same error as before, i. e.

Kernel panic - not syncing: VFS: Unable to mount root fs on
unknown-block(0,0)

Here's an entry from the init script from the initrd 

echo Creating /dev
mount -o mode=0755 -t tmpfs /dev /dev
mknod /dev/console c 5 1
 So I know there's a console being created

The first few lines of that file are:

mount -t proc /proc /proc
setquiet
echo Mounted /proc filesystem
echo Mounting sysfs
mount -t sysfs /sys /sys

You will notice, the message says Nash is starting, but the first "echo" isn't 
displayed.  Does that mean it can't mount proc?  I'm not sure I understand all 
I should know about proc but I would think it would be something built into the 
kernel and not a module.  In any case, AFAIK it isn't a ext3 file system.  I 
think I'm confused.  

/dev/hdb2 is the root.  It's the only partition used by FC4.  The system also 
has a Debian partition and an old Suse partition, but they won't be involved 
here.

So I went into the init script and put an echo as the first line.  No output.  
I'm assuming that the problem is occurring before Nash actually starts 
processing input, but what? 




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