> On 17 Jul 2020, at 18:20, David Teigland <teigland@redhat.com> wrote:
> 
> On Fri, Jul 17, 2020 at 09:04:32AM +0200, Henk Kraal wrote:
>> Hi all,
>> 
> 
>> I’ve run into an issue when trying to activate an LV which resides on a
>> read-only loop device. When I run lvchange -a y <LV Path> I get the
>> following error:
>> 
>>  Error writing device /dev/loop0p5 at 4096 length 512.
>>  bcache_invalidate: block (4, 0) still dirty
>>  Failed to write mda header to /dev/loop0p5 fd -1
>>  Failed to update old PV extension headers in VG recursor02-01-vg.
>>  Volume group "recursor02-01-vg" not found
>>  Cannot process volume group recursor02-01-vg
>> 
>> I’ve observed this issue when using LVM version 2.03.02
> 
>> Is there a way I can prevent the update of the extension headers when
>> activating the LV?
> 
> I don't think there's a way to tell that version to skip the header
> update.  A more recent verson of lvm should work, and let you use the PV
> without updating the header.  It will not attempt updates from commands
> which are not otherwise updating lvm metadata.
> Dave

Hi Dave,

Thank you for confirming that skipping the header update probably isn’t possible as I expected. I just wanted to make sure I wasn’t going down a rabbit hole needlessly.

The older LVM headers which I’m dealing with are part of the OS of hundreds of virtual servers which I don’t control. My task is to make the data on the read-only PV accesable for retrieval. A parameter to skip the update would’t have been the best option but I guess I need figure out if I can place a (temporary) writeable layer on top of the device to work around this.

Off course I’m open to idea’s if they come to the table ;)

With kind regards,

Henk