On Tue, Nov 1, 2011 at 11:38 AM, Sanjana Shari <sanjana.linux@xxxxxxxxx> wrote:
Hello,
I am trying to create two device mapper files for an underline blockdevice. One file( half1) will be mapped to the first half of the block-device. and the second half (half2) will be mapped to the rest of the space in the same block device.
1.Using dd command I have created a 100 MB file.
# dd if=/dev/zero of=dm_test bs=512 count=204800
2. associated it with loop device:
# losetup /dev/loop0 /tmp/dm_test
# blockdev --getsize /dev/loop0
204800
using dmsetup to create dm file.
# dmsetup create half --table "0 102400 linear /dev/loop0 0"
[root@bladelinux01 root]# dmsetup table half
0 102400 linear 7:0 0
[root@bladelinux01 root]# dmsetup info half
Name: half
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 0
Event number: 0
Major, minor: 253, 6
Number of targets: 1
[root@bladelinux01 root]# ls -l /dev/mapper/half
lrwxrwxrwx. 1 root root 7 Nov 1 01:44 /dev/mapper/half -> ../dm-6
But if I use the other part of the disk to map. The command is not successful
[root@bladelinux01 root]# dmsetup create half1 --table "102401 102399 linear /dev/loop0 102400"
device-mapper: reload ioctl failed: Invalid argument
Command failed
[root@bladelinux01 root]# dmsetup create half1 --table "102401 102399 linear /dev/loop0 0"
device-mapper: reload ioctl failed: Invalid argument
Command failed
The format used seems to be correct according to the man page of dmsetup. Please guide me. I am not sure what am I missing.
-- sanjana
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