LVM: what is dm-3?

[Luciano Rocha]

On Tue, Dec 04, 2007 at 03:28:10PM +0000, Timothy Murphy wrote:
> I got dozens of errors like
> ----------------------------------
> Dec  2 04:21:39 alfred kernel: EXT3-fs error (device dm-3):
> ext3_free_blocks: Freeing blocks not in datazone - block = 18318
> 17304, count = 1
> ----------------------------------
> the other day.
> I guess dm-3 means my 3rd LVM volume, which is /tmp .
> But how does one tell what dm-? corresponds to?

ls -l /dev/mapper:
brw-rw----  1 root disk 254,  5 2007-12-03 15:22 bit-f8
brw-rw----  1 root disk 254,  3 2007-12-03 15:23 bit-fc7
brw-rw----  1 root disk 254,  4 2007-12-03 15:22 bit-home
brw-rw----  1 root disk 254,  2 2007-12-03 15:23 bit-isos
brw-rw----  1 root disk 254,  0 2007-12-03 15:22 bit-swap
brw-rw----  1 root disk 254,  1 2007-12-03 15:22 bit-tmp
crw-rw----  1 root root  10, 63 2007-12-03 15:22 control
brw-rw----  1 root disk 254,  8 2007-12-03 15:26 crv
brw-rw----  1 root disk 254,  6 2007-12-03 15:25 linux
brw-rw----  1 root disk 254,  7 2007-12-03 15:25 off

Ignore "control", and the minor will identify the device. dm-3, in my
case, would be bit-fc7.

For more information, you can then run dmsetup table <device>:
$ sudo dmsetup table bit-fc7
0 15925248 linear 3:2 122683776
15925248 851968 linear 3:2 144900480

Which means a linear device using /dev/hda2 (major 3, minor 2: hda2).

-- 
lfr
0/0
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