[dm-crypt] Problem with udev and dmcrpyt

Milan Broz mbroz at redhat.com
Fri Jul 16 13:20:04 CEST 2010


On 07/16/2010 12:53 PM, Aaron Lewis wrote:
>> Update package which provides DM new rules. Yor distro should provide
>> it if they update udev.
> 
> Guess gentoo never provide such services.

It does, I am using it there:-)
maybe it is masked - that's bug, lvm must depend on new rules/udev then.


Long answer for the archive:

Formerly LVM/DM/cryptsetup managed dev nodes itself.

Later it started to utilize udev for this job, but the transition process
was very painfull and had many iterations. DM used some extension to block
device concept which were incompatible with udev view and vice versa.

So there were several versions of udev rules using various udev extensions,
some of these extension were removed from udev in later releases
(changing base device name is one of them).
It probably takes some time until all changes are propagated to distros...

Bu we finally iterated to situation that udev rules are now working properly
- with compromises on both sides.
(Only one problems remains - namely "watch" rule but is is not related to this problem).

Still, there is fallback mechanism in libdevampper - if the required device node
is not created by udev, it fallback to manual node creation.
(So even in misconfigured system it should work.)


The above means, that distro maintainers should start to compile lvm with udev
support, provide most recent udev rules (part of upstream lvm2/dm package)
and require new udev package which includes all require functionality.

Milan




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