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
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