[Fedora-xen] issues (part II)

[Steve Brueckner]

Michael Weiner wrote:
> OK, i am trying to get ttylinux going, reading some posts and howto's
> etc...but cant get the domU running. My ttylinux config looks like
> this:  
> 
> kernel = "/boot/vmlinuz-2.6.19-1.2911.fc6xen"
> ramdisk = "/boot/initrd- 2.6.19-1.2911.fc6xen.img"
> memory = 64
> name = "ttylinux"
> vif = ['']
> dhcp = "dhcp"
> disk = ['file:/opt/xen/ttylinux/ttylinux-xen,sda1,w']
> root = "/dev/sda1 ro"
> 
> and when i run xm create -c ttylinux.cfg i get the following after
> all the boot messages are done: 
> 
> Scanning logical volumes Reading all physical volumes.  This may
> take a while... No volume groups found  
> Activating logical volumes
>   Volume group "VolGroup00" not found
> Creating root device.
> Mounting root filesystem.
> mount: could not find filesystem '/dev/root'
> 
> i mounted the image and peeked at the fstab, i am unsure where the
> heck its getting VolGroup00 from. Can anyone lend any pointers to
> what i am doing wrong? I seem to get the same error no matter what
> pre-built image i am using.   

I see you've identified the problem as a non-existant LVG.  As you say, 
we need to figure out where the heck the Xen guest is getting the idea
to look for the LVG.  You said you looked at your guest's fstab...could
you post that for us?

However, if the reference to an LVG is not in the guest's GRUB (which 
is the guest's config file) and not in the guest's disk image, then 
maybe it's in the FC6 xen kernel or initrd?  That doesn't make much 
sense to me, but I do think that mixing an FC6 xen kernel with another 
distro's image could be a problem.

You might want to try building a guest by copying your FC6 host's files.
This would provide consistency between your kernel and file system.
You would use dd to create an image, mkfs to give it an ext3 file system,
mount it, then copy and minorly edit the file system.  Here's what I 
used to do (after the above 3 steps):

# mkdir /mnt/{proc,sys,tmp,selinux}
# chmod 777 /mnt/tmp/
# cp -ax /{root,dev,var,etc,usr,bin,sbin,lib,home} /mnt
# cp /mnt/etc/modprobe.conf /mnt/etc/modprobe.conf.bak
# echo > /mnt/etc/modprobe.conf
# mv /mnt/etc/fstab /mnt/etc/fstab.bak	
# vim /mnt/etc/fstab
/dev/sda1    /           ext3    defaults        1 1
none         /dev/pts    devpts  gid=5,mode=620  0 0
none         /dev/shm    tmpfs   defaults        0 0
none         /proc       proc    defaults        0 0
none         /sys        sysfs   defaults        0 0
/dev/sda2    swap        swap    defaults        0 0

I don't like the FC5 or FC6 Xen how-to's because they rely on Red Hat's
buggy tools to build guests.  I used to use the old FC4 how to because 
it showed more under the hood:

http://fedoraproject.org/wiki/FedoraXenQuickstartFC4

Here's some other old ones (remember I use an older version and avoid
using the rpms):

http://mitopia.net/index.php/Xen_3.0.2_Setup
http://www.neotextus.org/computing/virtualization/xen-fc3

Steve Brueckner, ATC-NY