#! /bin/sh -ex

: ${vgtag=@backup} ${vgprefix=vg-backup-}
: ${mntbkpdir=/mnt/bkp}
: ${STOREDIR=$mntbkpdir/store} ${METADIR=$mntbkpdir/meta}

vgs=$(vgs --noheadings -oname)
found=nil
for vg in $vgs; do
  case "$found,$vg" in
    nil,$vgprefix*)
      found=t
      tag=${vg#$vgprefix}
      ;;
    t,$vgprefix*)
      echo >&2 "$0: multiple backup volumes attached"
      exit 1
      ;;
  esac
done
case $found in
  nil) echo >&2 "$0: no backup volumes attached"; exit 1 ;;
esac
vg=$vgprefix$tag

vgchange -ay $vg
mount /dev/$vg/meta $METADIR

cryptop decrypt backup <$METADIR/crypt.blob |
	cryptsetup luksOpen --key-file=- /dev/$vg/crypt cbackup
mount /dev/mapper/cbackup $STOREDIR