domU kernel panic with root fs

domU kernel panic with root fs

[Bjoern Sessler]

Hi,

i installed xen 2.0 on my new installed gentoo box. xen0 works great, 
but i can't get domU kernel to mount root fs:

VFS: Cannot open root device "sda5" or unknown-block(8,5)
Please append a correct "root=" boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on 
unknown-block(8,5)

this happens with all root-fs i've tried, ttylinux and my cloned root 
from Xen0. ttylinux lives now on a hdc partition, the cloned root were 
lvm2 devices over kernlraid, which worked fine on my old gentoo with 
xeno-unstable.

fstab on ttylinux also points to sda5, sda5 also exists on Xen0, but 
also hda1 doesn't work. i also saw similar problem with wrong config of 
disk= parameter, but doesn't help me.

config looks like following for these parts:

# disk = [ 'phy:vg1/vm101,hda1,w', 'phy:vg1/vm101-swap,hda2,w', 
'phy:sdb7,hdc1,r!', 'phy:sdc5,hdc2,r!' ]
disk = [ "file:/machines/backup/ttylinux-xen,sda5,w" ]
#disk = [ 'phy:hdc6,hda1,w' ]

#ip = "192.168.1.101"
#netmask = "255.255.255.0"
#gateway = "192.168.1.1"

# Set root device.
root = "/dev/sda5 ro"

i believe i forgot something in the kernel for XenU but i started with 
default-config.

Thanks & Regards,
Björn




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Re: domU kernel panic with root fs

[Dan Cardamore]

Bjoern Sessler <bjoern.sessler <at> web.de> writes:
> 
> Hi,
> 
> i installed xen 2.0 on my new installed gentoo box. xen0 works great, 
> but i can't get domU kernel to mount root fs:
> 
> VFS: Cannot open root device "sda5" or unknown-block(8,5)
> Please append a correct "root=" boot option
> Kernel panic - not syncing: VFS: Unable to mount root fs on 
> unknown-block(8,5)


I'm having the exact same problem, does anyone know of a solution?

>From dom0 I can 'mount -o loop rootfs /mnt/loop' no problems.  It's an ext3
filesystem which my 2.4.27 kernel supports.

Dan



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Re: Re: domU kernel panic with root fs

[Ian Pratt]

> Bjoern Sessler <bjoern.sessler <at> web.de> writes:
> > 
> > Hi,
> > 
> > i installed xen 2.0 on my new installed gentoo box. xen0 works great, 
> > but i can't get domU kernel to mount root fs:
> > 
> > VFS: Cannot open root device "sda5" or unknown-block(8,5)
> > Please append a correct "root=" boot option
> > Kernel panic - not syncing: VFS: Unable to mount root fs on 
> > unknown-block(8,5)
> 
> 
> I'm having the exact same problem, does anyone know of a solution?
> 
> From dom0 I can 'mount -o loop rootfs /mnt/loop' no problems.  It's an ext3
> filesystem which my 2.4.27 kernel supports.

What does your "disks=" line look like?
file:/path/to/rootfs,sda5,w ?

In the boot log does it find the partitions on the virtual sda
OK? What happens if you export it as sda1 instead of sda5?

Ian


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Re: Re: domU kernel panic with root fs

[Mark Williamson]

Are you using devfs, udev or static /dev?  Only the latter two will work 
in domain != 0, so you may need to set one of those alternatives up.

HTH,
Mark

----------------------------------

"Boing!  Init 0" said Zebedee

On Tue, 23 Nov 2004, Dan Cardamore wrote:

> Bjoern Sessler <bjoern.sessler <at> web.de> writes:
>>
>> Hi,
>>
>> i installed xen 2.0 on my new installed gentoo box. xen0 works great,
>> but i can't get domU kernel to mount root fs:
>>
>> VFS: Cannot open root device "sda5" or unknown-block(8,5)
>> Please append a correct "root=" boot option
>> Kernel panic - not syncing: VFS: Unable to mount root fs on
>> unknown-block(8,5)
>
>
> I'm having the exact same problem, does anyone know of a solution?
>
> From dom0 I can 'mount -o loop rootfs /mnt/loop' no problems.  It's an ext3
> filesystem which my 2.4.27 kernel supports.
>
> Dan
>
>
>
> -------------------------------------------------------
> SF email is sponsored by - The IT Product Guide
> Read honest & candid reviews on hundreds of IT Products from real users.
> Discover which products truly live up to the hype. Start reading now.
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> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/xen-devel
>


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Re: Re: domU kernel panic with root fs

[Dan Cardamore]

On Tue, Nov 23, 2004 at 10:47:08PM +0000, Dan Cardamore wrote:
> Bjoern Sessler <bjoern.sessler <at> web.de> writes:
> > 
> > Hi,
> > 
> > i installed xen 2.0 on my new installed gentoo box. xen0 works great, 
> > but i can't get domU kernel to mount root fs:
> > 
> > VFS: Cannot open root device "sda5" or unknown-block(8,5)
> > Please append a correct "root=" boot option
> > Kernel panic - not syncing: VFS: Unable to mount root fs on 
> > unknown-block(8,5)
> 
> 
> I'm having the exact same problem, does anyone know of a solution?
> 
> From dom0 I can 'mount -o loop rootfs /mnt/loop' no problems.  It's an ext3
> filesystem which my 2.4.27 kernel supports.

I managed to figure out that this is related to devfs.  Whenever I have
devfs support compiled in it panics.  This is even if I don't mount
devfs (devfs=mount) and don't have "Automatically mount at boot time" in
the kernel config.

Anyone know why?  This is a significant nuisance if you're running a
gentoo system.

Thanks,

Dan
--
Dan Cardamore
dan@hld.ca


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Re: Re: domU kernel panic with root fs

[M.A. Williamson]

> I managed to figure out that this is related to devfs.  Whenever I have
> devfs support compiled in it panics.  This is even if I don't mount
> devfs (devfs=mount) and don't have "Automatically mount at boot time" in
> the kernel config.
> 
> Anyone know why?  This is a significant nuisance if you're running a
> gentoo system.

Unfortunately it's not possible to work around this by not mounting devfs. 
The virtual block device driver and DevFS do not play nicely together :-(

I suspect that DevFS enabled kernels don't like the VBD driver trying to 
register block devices without having first registered with the IDE or SCSI 
layers. As a result, virtual block devices don't get registered and hence 
you can't boot off them. It's not an issue in dom0, since you typically 
don't have VBDs, just real devices.

The feeling was that since DevFS is being phased out of the Linux kernel in 
favour of udev, it's probably not worth the work required to support it. 
All the XenLinux drivers should play nicely with udev / sysfs. I heard 
Gentoo was moving towards using udev but I don't know how far they've gone 
in that direction.

HTH,
Mark


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Re: Re: domU kernel panic with root fs

[Jan Kundrát]

Dan Cardamore wrote:
> Anyone know why?  This is a significant nuisance if you're running a
> gentoo system.

This isn't a problem as gentoo of course supports udev. See 
http://www.gentoo.org/doc/en/udev-guide.xml



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