device mapper Q

maybe this is more dm related than LVM2, but I could not finger out where to find more info/help....

after I turned to LVM2, I noticed, that the VG-specific subdirectory below /dev/<VG>/<LV> now contains symlinks to /dev/mapper/<VG>-<LV> devices.

Those devices also appear as /dev/dm-<N> again.

Q: who creates those links? For any reason I'm missing one of these link. Should I create it by hand?

If mounting an LV, which path should I prefer?

I used to use EXT2 labels and entered the LVs to the /etc/fstab using LABEL=<NAME>. With LVM2/DM the kernel now locates them as /dev/dm_<N> instead of /dev/<VG>/<LV>. Does it matter?

Is there any more DM background information around besides
http://sources.redhat.com/dm/, or do I have to analyze the C-code to learn more about it?

Dieter.

Dieter St�ken, con terra GmbH, M�nster
    [email protected]
    http://www.conterra.de/
    (0)251-7474-501

vgmknodes fixes things

Boot-up scripts should include vgscan --mknodes.

LVM2 will be updated at some point to recognise /dev/mapper/vg-lv names on the command line, but it doesn't yet - you must always use vg/lv.

dm-<minor_number> in sysfs/block is something I have no time for but seems pretty harmless.

But /dev/dm* sounds quite unnecessary.

devfs puts things into /dev/mapper automatically: udev should be configured to do the same - but it seems it can't because that would mean userspace call outs running scripts at critical times when they are not permitted to block (e.g. must not allocate any memory) or else could lock up the whole machine.
So everything should use libdevmapper (or equivalent), often via dmsetup, to keep /dev/mapper up-to-date.

Alasdair

[email protected]