Disk /dev/dm-0 doesn't contain a valid partition table

Hello,

I did an fdisk -l to review my partition table (see results below), and found four entries that end with "Disk /dev/dm-X doesn't contain a valid partition table." I don't recall seeing this in the past, so I believe it is something new.

I recently began using kernel 2.6.21.1, up from 2.6.9-42. I don't know if perhaps this had some effect, or if the entries are normal and I just never noticed them.

What led me here is that sar -d output includes four entries for hard drives (dev253 entries) when there are only three on my system. Fdisk is reporting four DM devices, so I'm thinking there is some correlation, but I don't know what.

Any constructrive feedback would be appreciated.

Thank you.

Disk /dev/sda: 1900.1 GB, 1900120375296 bytes 255 heads, 63 sectors/track, 231009 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1      231009  1855579761   8e  Linux LVM

Disk /dev/sdb: 146.1 GB, 146163105792 bytes 255 heads, 63 sectors/track, 17769 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *           1          38      305203+  83  Linux
/dev/sdb2              39       17769   142424257+  8e  Linux LVM

Disk /dev/sdc: 146.1 GB, 146163105792 bytes 255 heads, 63 sectors/track, 17769 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1       17769   142729461   8e  Linux LVM

Disk /dev/dm-0: 137.4 GB, 137405399040 bytes 255 heads, 63 sectors/track, 16705 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk /dev/dm-0 doesn't contain a valid partition table

Disk /dev/dm-1: 8388 MB, 8388608000 bytes
255 heads, 63 sectors/track, 1019 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk /dev/dm-1 doesn't contain a valid partition table

Disk /dev/dm-2: 146.1 GB, 146150522880 bytes 255 heads, 63 sectors/track, 17768 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk /dev/dm-2 doesn't contain a valid partition table

Disk /dev/dm-3: 1900.1 GB, 1900111986688 bytes 255 heads, 63 sectors/track, 231008 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk /dev/dm-3 doesn't contain a valid partition table

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Later kernels include dm devices in the list of partitions in proc, so fdisk will attempt to scan them for partition tables. It's not harmful, just noise.

If you don't like it & you've not configured anything to use /dev/dm-* devices directly (instead of /dev/mapper/* or /dev/<volgroup>/* or whatever) then you can reconfigure udev to not create the dm-* nodes.

- From memory, you need to comment out the rule that begins "KERNEL="dm-[0-9]*" in /etc/udev/rules.d/50-udev.rules, or, for newer udevs you can add ignore_device:

KERNEL=="dm-[0-9]*", ACTION=="add", OPTIONS+="ignore_device"

Those "dev253" entries are your device-mapper devices. Take a look at /dev/dm-* with ls -l and you will see that the major number is 253.

Kind regards,
Bryn.

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