[linux-lvm] Creating PV over a /dev/mapper device

[Roman Medina-Heigl Hernandez]

Hi,

I need to create a PV over a /dev/mapper device in order to create a
crypted LVM system (*) on a Debian Woody with 2.6.9 kernel.

I encrypted a partition (/dev/hda10) using DM-Crypt, getting
/dev/mapper/crypt10 device.

When trying to create PV, I got the following error:
jupiter:/# pvcreate /dev/mapper/crypt10
  /dev/mapper/crypt10: Couldn't find device.

I know how to temporaly fix the problem by adding the device to
/etc/lvm/.cache. But the problem is that I couldn't get it to be
permanent. I did several tests modifying /etc/lvm/lvm.conf and
re-running "vgchange" to re-read changes, but it didn't work.

I've tried different  lvm.conf configs like:

filter = [ "a|/dev/mapper/crypt.*|" ]
(cause I'd like to have crypt10, crypt11 and so on)

filter = [ "a|/dev/mapper/crypt10|" ]

filter = [ "a/.*/" ]

I mixed them with other directives like:
scan = [ "/dev" ]

scan = [ "/dev/mapper" ]

scan = [ "/dev/mapper" "/dev" ]


Nevertheless, when running vgscan, .cache is re-built without my crypt
device. What am I doing wrong? Is there any limitation on devices
scanned by vgscan?

I'm using this version of LVM:
jupiter:/# lvm version
  LVM version:     2.00.21 (2004-08-19)
  Library version: 1.00.15-ioctl (2004-04-07)
  Driver version:  4.1.0


(*) My idea of Crypted LVM system is to have crypted PVs and then
building LVM over them. This way I got total flexibility provided by
LVM and the security based on encryption (eg: I can extend/reduce a
live&mounted crypted fs on-the-fly). Anyone using a similar setup and
could/want to provide more ideas or feeback about this?

 Saludos,
 --Roman

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