[ale] Questionable output from fdisk -l

Scott Castaline hscast at charter.net
Tue Sep 25 16:48:20 EDT 2007


Daniel Kahn Gillmor wrote:
> On Tue 2007-09-25 14:20:23 -0400, Scott Castaline wrote:
>
>   
>> Disk /dev/dm-7 doesn't contain a valid partition table
>>
>> This goes through to dm-15, with the only difference being the
>> capacity/geometry listed for each. I also noticed in /dev that there
>> are block device files for dm-7 to dm-15. What do these represent? 
>>     
>
> the dm-X devices come from devmapper, the ultra-flexible Linux block
> device abstraction layer.  LVM makes much use of devmapper.  each LV
> (logical volume) in an LVM system has its own block device.
> Naturally, there's no reason to put a partition table on an LV, which
> explains why fdisk can't find a legitimate partition on any of
> /dev/dm-7 through /dev/dm-15.
>
> You can figure out which /dev/dm-* is which by matching device node
> major and minor numbers.  For example, on my system, /dev/dm-3 is my
> swap LV:
>
> [0 dkg at squeak ~]$ ls -la /dev/dm-5
> brw-rw---- 1 root disk 253, 5 2007-09-14 14:48 /dev/dm-5
> [0 dkg at squeak ~]$ ls -la /dev/mapper | grep ' 253, *5 '
> brw-rw----  1 root disk 253,  5 2007-09-14 14:48 squeak0-swap
> [0 dkg at squeak ~]$ 
>
> These major and minor node numbers might switch around across various
> manipulations of LVM (including reboots) so don't count on them to be
> static.
>
> hth,
>
>         --dkg
>   
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>
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Just checked each dm and found that all of them related to FC6 created 
LVM disks and none listed for ones created under Fedora7. Is that the 
way it should be? Some of what was created under FC6 are used under F7. 
So in other words, it's safe to ignore.



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