). I only realised later on that this device was actually part of a volume group, only noticing because the name of the device was dm-0. I still have access to the device, so I can try to extract another dd, if I knew a better way to backup the devicedd if=/dev/blocks/dm-0
I'm not sure how to proceed, because there are a lot of complications. First, the partition table was overwritten, and there is a new one in place. Second, I'm not quite sure how the logical volumes work. I believe that the physical drives are partitioned, marking the partition as LVM type, then LVM stores a configuration describing how to mount the logical volumes, then each logical volume is formatted using an ext4 filesystem. I don't know that there is any partition available to recover, here. I've had trouble retrieving the LVM configuration because this is an embedded system (Android). Because it's Android and the backing storage is flash, I'm also not quite sure how the CHS plays into it or even how testdisk uses it.
I've figured out that selecting "No partition" allows me to search for ext4 superblocks. TestDisk finds quite a few of those but when I try to examine them, I frequently pick the wrong one and have to redo a "deep search" to find them again
Am I going about this entirely wrong?
~ # fdisk -l /dev/block/dm-0
Note: sector size is 4096 (not 512)
Disk /dev/block/dm-0: 57.5 GB, 57588281344 bytes
255 heads, 63 sectors/track, 875 cylinders
Units = cylinders of 16065 * 4096 = 65802240 bytes
Disk /dev/block/dm-0 doesn't contain a valid partition table