[dm-crypt] crypt_get_uuid does not work as expected with plain volumes

Milan Broz gmazyland at gmail.com
Mon Jan 21 12:42:21 CET 2013


On 01/18/2013 07:29 PM, .. ink .. wrote:

> The source code and the test show crypt_get_uuid does not work as
> expected with plain volumes but does with truecrypt volumes and luks
> volumes. The expected behavior is to return NULL on volumes that do
> not support UUID.
> 
> with plain volumes,instead of "NULL",crypt_get_uuid returns
> "PLAIN-XYZ" where "XYZ" is the last component of the mapper path.

Hm. That function is confusing.

There are two UUIDs in fact
 - on disk (applies only to LUKS)
 - for activated device (aka DM-UUID)

DM-UUID is constructed from format type, on-disk UUID (if present) and
activated device name (so you are able to activate e.g. snapshot of LUKS
even with the same on-disk UUID).

crypt_get_uuid() was formerly designed to return DM-UUID but apparently I 
mixed up something here (PLAIN prefix should not be visible).

Well, I'll check what I can do here now and not break existing logic.

Thanks,
Milan


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