[mythtv-users] Errors with lvm2 (and/or evms and device_mapper)

[John Biundo]

Hi,

This isn't directly mythtv related, but I'm using lvm2 to support myth, 
and I believe it's commonly used, so I thought folks here might have an 
idea.  I'm also slightly suspicious that lvm may be the cause of a 
mysterious mythtv problem I'm having.

I'm running ubuntu (5.1 - breezy badger release).  I've installed lvm2, 
but I don't remember installing evms.  As far as I can tell from looking 
at dependencies, evms didn't get pulled in by the lvm2 install. It looks 
like evms may come pre-installed as part of ubuntu_base (a virtual 
package that pulls in the basic components of an ubuntu install).

I recently upgraded to a 2.6.15 kernel, and started seeing these 
messages in my dmesg output:

[17179593.368000] device-mapper: dm-linear: Device lookup failed
[17179593.368000] device-mapper: error adding target to table

They get repeated about 10 times.

Googling around shows these errors coming from some evms-related 
problems (possible conflict between evms/device_mapper and other 
"things" which want to "claim" devices...). It started getting pretty 
deep, especially since I don't *think* I need/use evms (I certainly 
don't use it explicitly; but there is some kind of relationship between 
lvm2 and device_mapper, and between device_mapper and evms and the 
dependencies aren't clear to me). The solution offered on the evms web 
site was to apply a patch, but the docs were spotty, it seemed like it 
was targeted to an early 2.6 kernel, and I suspected it might do more 
harm than good.

With that as background, is anyone else seeing this error? Or know what 
it means? I can't see any direct consequences, but I always hate to just 
ignore such ugly stuff in my system logs, and I do have some mysterious 
problems (with mythtv) for which I'd like to out any relationship with 
this problem.

Does anyone know if I can safely remove evms (when I try it, apt wants 
to also remove ubuntu_base, which is a virtual package, that supposedly 
can be safely removed)? Or might there be other consequences of removing 
evms and ubuntu_base that I need to be aware of?

Thanks for any advice.  I've also asked for help on the ubuntu forums, 
but haven't gotten any help there yet.

Cheers,
john