Re: [Xen-users] lomount + lvm

[Brian Krusic <brian@xxxxxxxxxx>]

John,

Worked like a charm, you rock!

How on Gods green Earth did you figure this out?

I woulda been stuck if it weren't for you, but now I am stocked.

- Brian




On Feb 6, 2009, at 7:56 AM, John Haxby wrote:

> Brian Krusic wrote:
> > Forgot, my conf files disk line of interest looks like this;
> >
> > disk = [ "tap:aio:/var/lib/xen/images/foo.img,xvda,w" ]
> First make sure your guest isn't running unless you want to trash  
> its file systems.
> losetup -f /var/lib/xen/images/foo.img
> losetup -a
> # Make a note of which device corresponds to /var/lib/images/foo.img,
> # 'll call it /dev/loopN but it's probably /dev/loop0
> kpartx -va /dev/loopN
>
> You'll get two new entries in /dev/mapper now: /dev/mapper/loopNp1  
> and /dev/mapper/loopNp2.   loopNp1 is /boot (asume you have got a  
> standard layout).   loopNp2 is a volume group.   You can just mount
> /dev/loopNp1 to poke around the /boot file system.
>
> Now
>
> vgscan
>
> This is where you might come unstuck.   The default volume group for  
> Red Hat and similar is "VolGroup00".  If your dom0 is using LVM and  
> so is the guest then you'll have do VolGroup00's and that's bad.    
> The best thing to do now is to boot a rescue image in a different  
> domU and rename the guest's volume group.  You'll need to undo the  
> kpartx and losetup (see below first) and when you've all finished  
> then you'll need to either fix up the guest's /boot/initrd*.img, / 
> etc/fstab and /boot/grub/grub.conf to hold the new name or you'll  
> have to rename it back again in the rescue guest.
> Anyway, assuming you don't get a clash:
>
> vgchange -ay VolGroup00
>
> The guest's file systems are now in /dev/VolGroup00 and you can  
> mount them as normal.
> To undo everything:
>
> 1.  umount any file systyems you mounted
> 2.  vgchange -an VolGroup00
> 3.  kpartx -d /dev/loopN
> 4. losetup -d /dev/loopN
>
> And next time you build a system, change the name of its volume  
> group so you don't wind up with two systems with the same volume  
> group name!   And I wish Red Hat had listened to me years ago when I  
> said that "VolGroup00" was a really poor idea.
> jch
>
>
>
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