Finding Encrypted LVM Physical Volumes

Charles Curley charlescurley at charlescurley.com
Tue Feb 12 10:09:40 MST 2013


Background: Once a year, I install a new drive to use in that year,
call it year Y. The previous year's drive (Y-1) stays on line but read
only so I can copy files from it as needed. The drive from the year
before (Y-2) is retired, but I have it should I ever need to go back to
it. That works just fine for non-LVM encrypted drives.

Last year I used LVM and encrypted (dm-mod) it. This year, I did the
same. I can boot to either Y or Y-1, but which ever one I boot too, I
can't read the other.

On hard drive Y, how do I make the physical volume on Y-1 visible?
fdisk -lu reveals a partition on Y-1 which is marked as "8e  Linux
LVM". pvscan only shows one PV. Judging both by the size and by the
fact that it's the one in use, I think it is showing the PV on Y.

root at dzur:~# pvscan
  PV /dev/dm-0   VG dzur   lvm2 [1.82 TiB / 0    free]
  Total: 1 [1.82 TiB] / in use: 1 [1.82 TiB] / in no VG: 0 [0   ]
root at dzur:~# pvs --all
  PV         VG   Fmt  Attr PSize PFree
  /dev/dm-0  dzur lvm2 a-   1.82t    0 
  /dev/dm-2            --      0     0 
  /dev/root            --      0     0 
  /dev/sda1            --      0     0 
  /dev/sda2            --      0     0 
  /dev/sda3            --      0     0 
  /dev/sdb1            --      0     0 
  /dev/sdb5            --      0     0 
root at dzur:~#

I conjecture the physical volume I want is on dm-2. How do I make it
visible?

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