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

  • To: xen-users@xxxxxxxxxxxxx
  • From: Alexandre Kouznetsov <alk@xxxxxxxxxx>
  • Date: Mon, 21 Oct 2013 13:54:04 -0500
  • Delivery-date: Mon, 21 Oct 2013 18:55:10 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>

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- 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.


Alexandre Kouznetsov

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