Fedora xen - Oct 2007 - VFS: Cannot open root device "sda1" or unknown-block(0, 0)

Hi, All

I followed the steps in Fedora7VirtQuickStart to install Xen on Fedora 7.
I downloaded couples of file system image from http://jailtime.org/. However,
every time I tried to create guest OS using those file system image, I got error
messages:

VFS: Cannot open root device "sda1" 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)

An example of Xen configure is:

kernel = "/boot/vmlinuz-2.6.20-2936.fc7xen"
memory = 256
name = "fedora.fc6"
vif = [ '''' ]
dhcp = "dhcp"
disk = [''file:/xen/fedora/fedora.fc6.img,sda1,w'',
''file:/xen/fedora/fedora.swap,
sda2,w'']
root = "/dev/sda1 ro"

Having been googling on this topic for a while, but still not getting the right
answer for it. Any help will be appreciated.

Thanks

Haifeng

On Thu, Oct 11, 2007 at 10:43:22AM -0700, Haifeng He
wrote:
> Hi, All
> 
> I followed the steps in Fedora7VirtQuickStart to install Xen on Fedora 7.
> I downloaded couples of file system image from http://jailtime.org/.
However,
> every time I tried to create guest OS using those file system image, I got
error
> messages:
> 
> VFS: Cannot open root device "sda1" 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)
> 
> An example of Xen configure is:
> 
> kernel = "/boot/vmlinuz-2.6.20-2936.fc7xen"
You don''t have a initrd image that contains the block device and
filesystem modules.

I expect the images you have downloaded have a valid grub configuration
inside it. If they have it, you can use:

bootloader = "/usr/bin/pygrub"

Instead of specifying a kernel that is outside the disk image. Pygrub
will be able to read grub configuration and kernel/initrd images from
inside the disk image.

-- 
Eduardo

On 10/11/07, Eduardo Habkost <ehabkost@redhat.com>
wrote:
> On Thu, Oct 11, 2007 at 10:43:22AM -0700, Haifeng He wrote:
> > Hi, All
> >
> > I followed the steps in Fedora7VirtQuickStart to install Xen on Fedora
7.
> > I downloaded couples of file system image from http://jailtime.org/.
However,
> > every time I tried to create guest OS using those file system image, I
got error
> > messages:
> >
> > VFS: Cannot open root device "sda1" 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)
> >
> > An example of Xen configure is:
> >
> > kernel = "/boot/vmlinuz-2.6.20-2936.fc7xen"
>
> You don''t have a initrd image that contains the block device and
> filesystem modules.
>
> I expect the images you have downloaded have a valid grub configuration
> inside it. If they have it, you can use:
>
> bootloader = "/usr/bin/pygrub"
>
> Instead of specifying a kernel that is outside the disk image. Pygrub
> will be able to read grub configuration and kernel/initrd images from
> inside the disk image.
>
Thank you for your reply. I tried to include bootloader =
"/usr/bin/pygrub"
in my configuration but I got an error message "Error: Boot loader
didn''t return any data!".
I was able to boot the same image on a Ubuntu system with Xen
installed from source.
Do I need to do something special on Fedora-Xen? Or there is a way that I
can add block device and filesystem modules into the initrd image?

Thanks
Haifeng
> --
> Eduardo
>

On Fri, Oct 12, 2007 at 10:06:43AM -0700, Haifeng He wrote:
<snip>
> >
> > I expect the images you have downloaded have a valid grub
configuration
> > inside it. If they have it, you can use:
> >
> > bootloader = "/usr/bin/pygrub"
> >
> > Instead of specifying a kernel that is outside the disk image. Pygrub
> > will be able to read grub configuration and kernel/initrd images from
> > inside the disk image.
> >
> 
> Thank you for your reply. I tried to include bootloader =
"/usr/bin/pygrub"
> in my configuration but I got an error message "Error: Boot loader
> didn''t return any data!".
> I was able to boot the same image on a Ubuntu system with Xen
> installed from source.
> Do I need to do something special on Fedora-Xen? Or there is a way that I
> can add block device and filesystem modules into the initrd image?
I took a look at the config file shipped with Fedora images on the site
you mentioned. It looks like it expects you to have a pre-compiled domU
kernel that contains all needed modules, on you host /boot directory. I
don''t know which kernel image the author of those images expects you
to use.

Some things you can try:

- Checking the instructions on the README.txt inside the image, as noted
  on <http://jailtime.org/download:fedora:fc6>. Maybe there are some
  clues there; or
- Try to generate a initrd that will contain all needed modules. You can
  play with the --omit-* and --with options of mkinitrd to get a initrd
  with the right modules; or
- Try using the Xen kernel and initrd from the FC-6 repository:
  http://download.fedora.redhat.com/pub/fedora/linux/core/6/i386/os/images/xen/
  or
- Get a domU kernel with all needed modules compiled as builtin (so
  you don''t need a initrd) from somewhere, or compile a domU kernel
this
  way; or
- Put a valid grub configuration (and a kernel-xen package) inside the
  image, to get pygrub to work; or
- Use virt-manager and install your own FC-6 system instead of using
  the downloaded image.

-- 
Eduardo