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[Xen-users] Troubles converting a pv host from dom0-hosted kernel to sel

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Troubles converting a pv host from dom0-hosted kernel to self-contained kernel
From: Guillaume Rousse <Guillaume.Rousse@xxxxxxxx>
Date: Tue, 21 Jul 2009 17:17:17 +0200
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Hello list.

I have a perfectly working PV host, with this configuration:

kernel = "/boot/vmlinuz-"
ramdisk = "/boot/initrd-"
root = "/dev/sda1 ro"
extra = "(hd0)/boot/grub/menu.lst"
memory = 256
maxmem = 512
name = "sexonthebeach"
uuid = "f36962f5-0dec-4708-84a0-f5b4dea48d34"
disk = [ 'phy:/dev/vg0/sexonthebeach,sda1,w' ]
vif = [ 'mac=00:16:3e:00:00:13, bridge=services' ]

As this involves heavy coupling between dom0 and domU, I'm trying to make the PV host self-contained. AFAIK, the only way to do it is via pvgrub.

Here is the configuration:

kernel = "/usr/lib/xen/boot/pv-grub-x86_64.gz"
extra = "(hd0)/boot/grub/menu.lst"
memory = 256
maxmem = 512
name = "sexonthebeach"
uuid = "f36962f5-0dec-4708-84a0-f5b4dea48d34"
disk = [ 'phy:/dev/vg0/sexonthebeach,sda1,w' ]
vif = [ 'mac=00:16:3e:00:00:13, bridge=services' ]

The domU grub configuration:

timeout 10
color black/cyan yellow/cyan
default 0

title linux
kernel (hd0)/boot/vmlinuz-server root=/dev/xvda1
initrd (hd0)/boot/initrd-server.img

First issue: I found than it was mandatory to use root=/dev/xvda1 in order to mount root device when booting, despite the partition being exported as sda1 according to domU configuration. Is this normal ?

Second issue, the boot stop at root partition mount time, trying to force fsck:
[/sbin/fsck.ext3 (1) -- /] fsck.ext3 -a -a /dev/sda1
fsck.ext3: No such file or directory while trying to open /dev/sda1
The superblock could not be read or does not describe a correct ext2
filesystem.  If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>

This happens whatever device I use for root partition in domU /etc/fstab (/dev/sda1 or /dev/xdva1). However, I can perfectly mount /dev/vg0/sexonthebeach as an ext3 partition in domU. Morevoer, the emergency shell has expected content monted under / in both case...

Last question, loosely related to this problem: is there a way to easily convert a partition-based host to a disk-based host (phy:/dev/vg0/foo,sda1 -> phy:/dev/vg0/foo,sda) ?

Guillaume Rousse
Service des Moyens Informatiques
INRIA Saclay - Île-de-France
Parc Orsay Université, 4 rue J. Monod
91893 Orsay Cedex France
Tel: 01 69 35 69 62

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