lvm boot from second volume group

[list user]

Paul Howarth wrote:
> list user wrote:
> 
>> Paul Howarth wrote:
>>
>>> list user wrote:
>>>
>>>> Hi everybody!
>>>>
>>>> I'm using fc4 and working with xen, and it works great, but I've 
>>>> come upon an issue that I don't know how to resolve.
>>>>
>>>> I've many different images and configurations using lvm and grub to 
>>>> multi-boot.  To keep things easy (for me) I use IDE drives and the 
>>>> motherboard's built-in IDE interfaces.
>>>>
>>>> I added another volume group, vg1, to my lvm setup, and placed an 
>>>> fc4 tree on it, and added an entry to grub.conf.  However, when I 
>>>> try to boot into that image it fails.  Same image on volume group 0 
>>>> (vg0) will boot.
>>>>
>>>> Has anybody managed to use grub to boot from a second volume group?
>>>>
>>>> I suspect that it may be an initrd issue, but don't know for sure.
>>>>
>>>> Any pointers or suggestions would be appreciated.
>>>
>>>
>>>
>>> I don't really get what you're asking. grub doesn't understand LVM at 
>>> all AFAIK, it just boots the kernel/initrd from a regular partition 
>>> (/boot) and passes parameters to that kernel to tell it where to find 
>>> the root filesystem.
>>>
>>> So when you say "boot into that image", what do you mean? Where is 
>>> the kernel and initrd, and what does the grub.conf entry look like?
>>
>>
>> Thanks for the reply, Paul.  It took me a while to get back to you
>> because I ran through this again to make sure of what I was(n't) seeing.
>>
>> My original install uses lvm and was installed to /dev/vg0/fc4.  Using
>> the lvm tool "vgcreate" I made /dev/vg1, then lvcreate to make
>> /dev/vg1/fc4.  Once /dev/vg1/fc4 was formatted and mounted I copied
>> vg0/fc4 to vg1/fc4, edited vg1/fc4/etc/fstab to point to the correct lv.
>>
>> Now booting into either shows that both lv's are seen and recognized
>> during the boot process, but booting into vg1/fc4 fails after the line
>> "Creating root device".
>>
>> Everything _seems_ to be OK but just won't work.  So, as an experiment,
>> I tried a clean install and this is what was found.
>>
>> During the partitioning section /dev/vg1 was not there; it was shown as
>> a raw partion (/dev/hda3) of type ext3 so I turned it into an lvm and
>> proceeded with the install.  It now boots into /dev/vg1/fc4!
>>
>> In summary, during the boot process into either volume group both volume
>> groups were seen and recognized, but the one that was built using the
>> lvm tools wouldn't boot successfully, and then going through the install
>> process showed that the installer didn't recognize the second volume
>> group as an "lvm" but as "ext3".
>>
>> I haven't a clue as to why.  I don't understand the inner workings of
>> lvm and how they identify themselves or are identified.  Is this a
>> labeling issue?  Is it perhaps that the lvm created using the tools
>> didn't remark the partition table with type "lvm"?  Dunno.
>>
>> Now that it has been marked as "lvm" I will try copying another instance
>> of fc4 onto vg1 and try booting into it to see if that solved the
>> original problem.
>>
>> At any rate, I will post my results.

Hoorah!  Once the raw partition had been marked as type "lvm" the boot 
process completed successfully.

> 
> 
> When you created the second volume group (vg1), did you just do a 
> pvcreate on the target partition, which had previously been used by an 
> ext3 filesystem? From your description above, it sounds like that's what 
> you did, without using fdisk to change the partition type to "Linux LVM" 
> instead of ext3. So I'd guess the boot process didn't look for LVM 
> volumes on partitions not marked as such. It's a theory anyway!

Seems like a good theory to me!

In the future I will add a fdisk step to my process.

Thanks, Paul

:m)

> 
> Paul.
>