How to fix two disks with the same Volume Group?

[Da Rock]

On Thu, 2008-03-20 at 10:22 +0000, Luciano Rocha wrote:
> 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
> ...
> 

Good to know- a shortcut. Is this under repair on the install cd?

> > 
> > 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).
> 

Surely not if you've just changed the name using the repair disk? But
very succinctly put- I've only done this once and it took several hours
following from instructions on a page. I had trouble remembering the
exact steps myself.

> > 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.
> 

Yes, I do apologise for the confusion. I rectified that in a later
email.

> > 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

You don't think setting it to the machine name is any good? Given
current install procedures, what do you suggest to prevent this?
Obviously something manually.