[dm-crypt] LUKS is written to a device with no partition table. Is it possible to add a partition table?

David Christensen dpchrist at holgerdanske.com
Wed Apr 20 06:14:24 CEST 2016

On 04/19/2016 12:08 PM, Joe Hillenbrand wrote:
> I have a 12TB hardware RAID5 external hard drive array.

4 @ 4 TB HDD's?  What is the make/ model of external hard drive array? 
What is the make/ model of the drives?  What is/ are the interface(s) to 
your computer?

> I had initially planned to only ever encrypt data to the device, but now I
> need about half encrypted and half not.

2 @ 4 TB => 4 TB RAID1 and 2 @ 4 TB => 4 TB RAID1 encrypted?

> The device is `/dev/sdd`. It mounts as `fatty`.
> There is no partition table.
> As you can see LUKS starts at the first byte of the device.
> There is a btrfs filesystem on the LUKS device and I resized it down to 4TB.
> I can't really move the data anywhere, because it's too big and would
> require buying more hardware.
> Is it possible to add a partition table without losing the data?

A few years back I tried to be a cowboy and rearrange my large data 
without buying additional hardware.  I lost data.  I then bought enough 
hardware to implement daily backups with dual redundant copies:

1. I like large desktop HDD's for backups. If you use 8 TB HDD's for 
backups, 2 @ 4 TB RAID1's should fit onto one backup drive.

2. Mobile docks both protect the drives and make it easy to move the 
drives around (e.g. off-site rotation):


I realize that's a big investment -- 420+ USD per drive plus rack.  My 3 
@ 3 TB drives with racks cost me ~800 USD.  It was worth it.


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