Re: Replace a failed block device with null PV in an LVM VG

[David Pottage <david@chrestomanci.org>]

On 2021-03-24 12:37, Reco wrote:
> Hi.
>
> On Wed, Mar 24, 2021 at 10:26:49AM +0000, David Pottage wrote:
> > Is there a way to assemble the VG and mount those ext4 filesystems in
> > such a way that read attempts from the missing PV will return zeros,
> > but the rest of the filesystem will work?
>
> Try this:
>
> vgchange --activationmode partial -ay
> lvs
> # immediately dump logical volume in question somewhere with cat/dd
> cat /dev/<vg>/<lv> > lv.img
> vgchange -an <vg>
> # run fsck -f on a copy of logical volume
> fsck -f lv.img
> # try mounting it
> mount -o loop lv.img /<mountpoint>


Thanks, that partly worked. It was an older version of LVM2, so I had to 
modify the command line syntax to "vgchange --partial -ay <VG>"

I was then able to mount the damaged volumes and get back nearly half of 
the lost files. I had a separate record of SHA1 checksums of all the 
lost files and all the recovered files have been checked and are 
undamaged.

Thanks for your help.

--
David Pottage