[Xen-users] mkinitrd problem when LVM volume group names differ between Dom0 and DomU

[Mike Freemon <mfreemon@xxxxxxxxxxxxx>]

How can I make "mkinitrd" generate a correct ramdisk image when the LVM 
volume group names differ between the Dom0 and DomU?
The details:

In Dom0, the root filesystem is LVM in volume group "VGShark", as follows:

# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VGShark-LogVol00
                      450G  119G  308G  28% /
/dev/sda1              99M   45M   49M  48% /boot
tmpfs                 1.9G     0  1.9G   0% /dev/shm

In the DomU, the root filesystem is LVM in volume group "VolGroup00".

Back in Dom0, I run the following to create the initrd...

#mkinitrd -f initrd-2.6.16.29-xen.img 2.6.16.29-xen

...which produces the following (snippet) in the generated "init" file in 
the ramdisk image:
echo Making device-mapper control node
mkdmnod
mkblkdevs
echo Scanning logical volumes
lvm vgscan --ignorelockingfailure
echo Activating logical volumes
lvm vgchange -ay --ignorelockingfailure  VGShark
resume /dev/VGShark/LogVol01
echo Creating root device.
mkrootdev -t ext3 -o defaults,ro /dev/VGShark/LogVol00
echo Mounting root filesystem.
mount /sysroot
echo Setting up other filesystems.
setuproot
echo Switching to new root and running init.
switchroot

The DomU config file is:

kernel = "/boot/vmlinuz-2.6.16.29-xen"
ramdisk = "/boot/initrd-2.6.16.29-xen.img"
root = "/dev/VolGroup00/LogVol00 ro"
name = "minnow"
memory = "512"
disk = [ 'file:/var/vm/minnow/disk0.img,xvda,w' ]
vif = [ 'mac=00:16:3e:00:e6:8f' ]
uuid = "7e6aa8bb-37da-3a7f-e72e-63290fcf2713"

..which produces the following error at domU boot time:

Making device-mapper control node
Scanning logical volumes
  Reading all physical volumes.  This may take a while...
  Found volume group "VolGroup00" using metadata type lvm2
Activating logical volumes
  Unable to find volume group "VGShark"
Creating root device.
Mounting root filesystem.
mount: could not find filesystem '/dev/root'
Setting up other filesystems.
Setting up new root fs
setuproot: moving /dev failed: No such file or directory
no fstab.sys, mounting internal defaults
setuproot: error mounting /proc: No such file or directory
setuproot: error mounting /sys: No such file or directory
Switching to new root and running init.
unmounting old /dev
unmounting old /proc
unmounting old /sys
switchroot: mount failed: No such file or directory
Kernel panic - not syncing: Attempted to kill init!

So --

Here is the /etc/fstab (in Dom0):

#cat fstab
/dev/VGShark/LogVol00   /                       ext3    defaults        1 1
LABEL=/boot             /boot                   ext3    defaults        1 2
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
tmpfs                   /dev/shm                tmpfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
sysfs                   /sys                    sysfs   defaults        0 0
/dev/VGShark/LogVol01   swap                    swap    defaults        0 0

I copy this file to create fstab.domU, and change the references to VGShark 
to VolGroup00, which is:
#cat fstab.domU
/dev/VolGroup00/LogVol00   /                    ext3    defaults        1 1
LABEL=/boot             /boot                   ext3    defaults        1 2
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
tmpfs                   /dev/shm                tmpfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
sysfs                   /sys                    sysfs   defaults        0 0
/dev/VolGroup00/LogVol01   swap                 swap    defaults        0 0

This matches exactly what DomU is expecting.

I rebuild initrd with the following command:

# mkinitrd -f --fstab=/etc/fstab.domU initrd-2.6.16.29-xen.img 2.6.16.29-xen

...which produces the following (snippet) in the generated "init" file in 
the ramdisk image:
mkblkdevs
resume /dev/VolGroup00/LogVol01
echo Creating root device.
mkrootdev -t ext3 -o defaults,ro /dev/VolGroup00/LogVol00
echo Mounting root filesystem.
mount /sysroot
echo Setting up other filesystems.
setuproot
echo Switching to new root and running init.
switchroot

I try again to boot the DomU with the same config file listed above and I 
get this error:
Creating root device.
Mounting root filesystem.
mount: could not find filesystem '/dev/root'
Setting up other filesystems.
Setting up new root fs
setuproot: moving /dev failed: No such file or directory
no fstab.sys, mounting internal defaults
setuproot: error mounting /proc: No such file or directory
setuproot: error mounting /sys: No such file or directory
Switching to new root and running init.
unmounting old /dev
unmounting old /proc
unmounting old /sys
switchroot: mount failed: No such file or directory
Kernel panic - not syncing: Attempted to kill init!

Next --

I modify the generated "init" file in the ramdisk image to the following 
(replace VGShark with VolGroup00):
mkdmnod
mkblkdevs
echo Scanning logical volumes
lvm vgscan --ignorelockingfailure
echo Activating logical volumes
lvm vgchange -ay --ignorelockingfailure  VolGroup00
resume /dev/VolGroup00/LogVol01
echo Creating root device.
mkrootdev -t ext3 -o defaults,ro /dev/VolGroup/LogVol00
echo Mounting root filesystem.
mount /sysroot
echo Setting up other filesystems.
setuproot
echo Switching to new root and running init.
switchroot

I rebuild the initrd image, and change the ramdisk line in the domU config to:

kernel = "/boot/vmlinuz-2.6.16.29-xen"
ramdisk = "/boot/initrdDomU.img"
root = "/dev/VolGroup00/LogVol00 ro"
name = "minnow"
memory = "512"
disk = [ 'file:/var/vm/minnow/disk0.img,xvda,w' ]
vif = [ 'mac=00:16:3e:00:e6:8f' ]
uuid = "7e6aa8bb-37da-3a7f-e72e-63290fcf2713"

...and the DomU boots up!

The conclusion I draw is that mkinitrd is not creating a good ramdisk image.

How can I make mkinitrd generate a correct ramdisk image when the volume 
group names differ between the Dom0 and DomU?
TIA,

- Mike


_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users