Re: [Xen-users] adding entry in Grub for xen

[Alexandre Kouznetsov <alk@xxxxxxxxxx>]

El 21/10/13 09:20, Bhadresh Udani escribió:
> I have downloaded linux 2.6.18 and xen 3.3.1 and compiled xen kernel.
> I have added entry in grub file as shown below:
>   title Xen 3.3 / XenLinux 2.6
>          root (hd00,0))
>          kernel /xen.gz
>          module /vmlinuz-2.6.18.8-xen ro root=/dev/sda3
>
> While booting using above entry, it gives following error:
> VFS: Cannot open a root device "sda3" 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)
>
> I have tried to change sda3 to xvda also, but no luck. I see few places
> initrd (ramfs) entry in some of the examples. but there is no file
> created while i did build.
>
> Any help is appreciated. May i know what i am missing while adding entry
> in grub file?
I bet the problem is caused by a missing initrd, so your system lack 
support for the hard disks controller on the stage of mounting root 
filesystem. initrd image for a xen-enabled kernel is normally provided 
with the kernel itself, via a pre-built kernel image package, special 
make option over your kernel source tree, or a distribution-specific 
generation script. It does not come from Xen.
Although, there is a way to avoid initrd at all compiling everything 
needed for booting into the kernel. This option drastically lacks 
flexibility and normally not used, unless you know what you are doing 
and have specific need.
Please consider this example from menu.lst of one of my older systems:

title           Xen 3.0.3-1-amd64 / Debian GNU/Linux, kernel 
2.6.18-6-xen-amd64
root            (hd0,0)
kernel          /boot/xen-3.0.3-1-amd64.gz dom0_mem=384M
module          /boot/vmlinuz-2.6.18-6-xen-amd64 
root=UUID=fe959da7-205c-406a-903d-2da8248c286c ro console=tty0
module          /boot/initrd.img-2.6.18-6-xen-amd64

Please note the following details:
initrd is specified by a second "module" statement.
I do not use a separate partition for /boot.
Block device for root filesystem is specified by it's UUID, which might 
be not needed in your case (correct /dev/sdXN should work), but worth to 
try.
Xen and kernel have extra options specified, the are not critical to get 
over the mounting root filesystem stage.
Greetings.

--
Alexandre Kouznetsov


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