[linux-lvm] System won't create devices from volume group : advice on dmsetup create command required (or alternative solution)
junk4 at klunky.co.uk
Wed Mar 3 10:43:34 UTC 2010
I am moving an LVM between two machines but the new machine won't
create the devices.
** Source machines set-up:
LVM created on XEN server as one volume group.
The Volume Group was then presented to a XEN host via xm block-attach.
The XEN host then used fdisk to create two partitions on the new device
(/dev/xvdd1 and /dev/xvdd2) [I wish they had not done this!]
The devices were removed from the XEN host (xm block detach) and then
vgchange -a n mds (mds is the vg)
The discs were unpresented from the source machine.
** Target machine set-up:
The discs were presented from the target machine.
# pvscan [results as expected]
Reading all physical volumes. This may take a while...
Found volume group "mds" using metadata type lvm2
# vgchange -a y mds
# vgdisplay mds
--- Volume group ---
VG Name mds
Metadata Areas 4
Metadata Sequence No 2
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 1
Open LV 0
Max PV 0
Cur PV 4
Act PV 4
VG Size 209.95 GB
PE Size 4.00 MB
Total PE 53746
Alloc PE / Size 53735 / 209.90 GB
Free PE / Size 11 / 44.00 MB
VG UUID TnUWZQ-kK5S-iLTR-U0C5-NYHk-96cw-smDLm2
However, the devices are not created:
# ls /dev/mapper | grep mds
brw------- 1 root root 253, 11 Mar 3 11:17 /dev/mapper/mds-mds
# fdisk -l /dev/mds/mds
Disk /dev/mds/mds: 225.3 GB, 225380925440 bytes
255 heads, 63 sectors/track, 27401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/mds/mds1 1 24152 193992907 83 Linux
/dev/mds/mds2 24152 27401 26105594 83 Linux
# ls -l /dev/mds/mds*
lrwxrwxrwx 1 root root 19 Mar 3 11:17 /dev/mds/mds -> /dev/mapper/mds-mds
I think that I have to use dmsetup to create the devices: dmsetup create
However, I have no idea where to start.
I would be very grateful if someone could advice me on how to proceed,
because I have a finite time to keep this UAT environment down.
Best regards, J.
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