How to fix two disks with the same Volume Group?

Luciano Rocha strange at nsk.no-ip.org
Thu Mar 20 10:22:35 UTC 2008


On Thu, Mar 20, 2008 at 08:12:05PM +1000, Da Rock wrote:
> 
> On Thu, 2008-03-20 at 08:48 +0000, Chris G wrote:
> > I have just had Fedora 7 re-installed on my work desktop as the old
> > disk drive was slowly failing.
> > 
> > I need to access the old disk if I can, it's still in the system and
> > visible but the person who installed it didn't change volume groups so
> > I have two disk drives with the same volume group.  How do I change the
> > name of the old disk's volume group so I can mount it and see it?
> > 
> > Running vgscan returns:-
> > 
> >   Reading all physical volumes.  This may take a while...
> >   WARNING: Duplicate VG name VolGroup00: Existing
> > P6sqp0-rIos-JYmi-8L32-ymtN-LzB4-g5BdLL (created here) takes precedence
> > over TdWFKp-H4tw-UrVq-Jmre-26hv-zmyE-IZXQLI
> >   Found volume group "VolGroup00" using metadata type lvm2
> >   Found volume group "VolGroup00" using metadata type lvm2
> > 
> > -- 
> > Chris Green
> > 
> 
> Actually its a real pain the ***. Bee there, done that. For future
> reference- when installing change the name of the fs to the machine
> name. Saves these sorts of issues, I found this out the hard way and
> came across this gem on the net.
> 
> Forgive me for going into a taboo area, but the way I fixed it (vgrename
> won't work in this case I reckon- please try though) was to throw an
> Ubuntu live disk in the cdrom and boot, download lvm2 from the Ubuntu
> repo (Debian won't work- although if Debian make a live disk then use
> their repo). Run update software and run the vgrename from there. If you
> need root password then (it seems a little redundant but anyway... it
> works for me...) go to administration and users and change the root
> password there.

You can use the install/recovery disc for Fedora. On the command line,
you'll have to prefix the lvm commands with lvm, like this:

lvm pvscan
lvm vgscan
lvm vgchange
...

> 
> Seeing you can't have both disks with the same name at the same time,
> you'll need to change the name of your current disk. If you reboot it
> will fail once you've renamed, so make sure you change your grub, init
> file, and mount your main lvm partition and change your inittab file to
> match your new name.

You mean:
1. edit grub.conf, change root= to the new name
2. edit etc/fstab, change swap, root, etc. to use new name
3. re-create initrd, as it has the vg name hardcoded:
   mkinitrd -f -v /boot/initrd-`uname -r`.img `uname -r`

You can do this while the system is running, and then reboot. No need
for recovery/lice cd (if everything goes fine; you'll need it if the
system no longer boots).

> This is very involved, I know, so ensure you have an instruction web
> page up there to follow from. Run a google search on how to use Ubuntu
> to rectify an lvm. If you find the right one, it'll have all the
> instructions you need- except for the inittab: found that out the hard
> way. If you don't fix that, you get a selinux error and it won't boot
> properly.
> 

I think you're confusing inittab with fstab (or initrd). The inittab
file has no reference to the root device.

> Good luck

Yeah, that's always needed.

I'd suggest that new Fedora releases create a random name for the VG and
that their initrd/nash support getting the vg from the root= kernel
command line.

Regards,
Luciano Rocha

-- 
lfr
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