Implement devicemapper storage

[rgayon]

Source: https://www.slideshare.net/JoelLathrop2/docker-forensics

Once LVM has settled:

cont_id="whatevs"
m=$(cat /var/lib/docker/image/devicemapper/layerdb/mounts/$cont_id/mount-id)
$d=$(jq ".device_id" /var/lib/docker/devicemapper/metadata/$m)
$size=$(jq ".size" /var/lib/docker/devicemapper/metadata/$m)
dmsetup create thin-$cont_id --table "0 $s thin /dev/mapper/docker-thinpool $d"
mount -o ro,nouuid /dev/mapper/thin-$cont_id /mnt/$cont_id/