Is there a simple way to move/copy a logical volume from one volume group to another? (LVM2)
If you can arrange for the logical volume to be on a separate subset of physical volumes from the rest of the source volume group (lvconvert sourcevg/sourcelv /dev/pv1 ...
may help), you can use vgsplit
to split off the lv into a new vg and vgmerge
to merge the new vg into the target vg.
Although LVM has a mirroring feature, you can't (sanely) use it to make a copy between volume groups, because both legs of the mirror must live on the same vg and the association can't be broken.
You can copy an LVM volume to another the way you'd copy any volume to another: create a target lv of the appropriate size, then copy the contents with dd if=/dev/sourcevg/sourcelv of=/dev/targetvg/targetlv bs=4M
. If the source volume is active, you can leverage LVM to make a consistent copy: first take a snapshot of the source lv with lvcreate -s
, then copy the snapshot.
pvmove -n lvol1 /dev/sdb1 /dev/sdc1
pvmove can move data between physical volumes: LVM Administrator's Guide
As of the LVM in Debian stretch (9.0), namely 2.02.168-2, it's
possible to do a copy of a logical volume across volume groups using a
combination of vgmerge
, lvconvert
, and vgsplit
. Since a move is
a combination of a copy and a delete, this will also work for a move.
Alternatively, you can use pvmove
to just move the volume.
A complete self-contained example session using loop devices and
lvconvert
follows.
Summary: we create volume group vg1
with logical volume lv1
, and vg2
with lv2
, and make a copy of lv1
in vg2
.
Create files.
truncate pv1 --size 100MB
truncate pv2 --size 100MB
Set up loop devices on files.
losetup /dev/loop1 pv1
losetup /dev/loop2 pv2
Create physical volumes on loop devices (initialize loop devices for use by LVM).
pvcreate /dev/loop1 /dev/loop2
Create volume groups vg1
and vg2
on /dev/loop1
and /dev/loop2
respectively.
vgcreate vg1 /dev/loop1
vgcreate vg2 /dev/loop2
Create logical volumes lv1
and lv2
on vg1
and vg2
respectively.
lvcreate -L 10M -n lv1 vg1
lvcreate -L 10M -n lv2 vg2
Create ext4 filesystems on lv1
and lv2
.
mkfs.ext4 -j /dev/vg1/lv1
mkfs.ext4 -j /dev/vg2/lv2
Optionally, write something on lv1
so you can later check the copy was
correctly created. Make vg1
inactive.
vgchange -a n vg1
Run merge command in test mode. This merges lv1
into lv2
.
vgmerge -A y -l -t -v <<destination-vg>> <<source-vg>>
vgmerge -A y -l -t -v vg2 vg1
And then for real.
vgmerge -A y -l -v vg2 vg1
Then create a RAID 1 mirror pair from lv1
using lvconvert
. The
<> argument tells lvconvert
to make the mirror copy
lv1_copy
on /dev/loop2
.
lvconvert --type raid1 --mirrors 1 <<source-lv>> <<dest-pv>>
lvconvert --type raid1 --mirrors 1 /dev/vg2/lv1 /dev/loop2
Then split the mirror. The new LV is now lv1_copy
.
lvconvert --splitmirrors 1 --name <<source-lv-copy>> <<source-lv>>
lvconvert --splitmirrors 1 --name lv1_copy /dev/vg2/lv1
Make vg2
inactive.
vgchange -a n vg2
Then (testing mode)
vgsplit -t -v <<source-vg>> <<destination-vg>> <<moved-to-pv>>
vgsplit -t -v /dev/vg2 /dev/vg1 /dev/loop1
For real
vgsplit -v /dev/vg2 /dev/vg1 /dev/loop1
Resulting output:
lvs
[...]
lv1 vg1 -wi-a----- 12.00m
lv1_copy vg2 -wi-a----- 12.00m
lv2 vg2 -wi-a----- 12.00m
NOTES:
1) Most of these commands will need to be run as root.
2) If there is any duplication of the names of the logical volumes in
the two volume groups, vgmerge
will refuse to proceed.
3) On merge:
Logical volumes in `vg1` must be inactive
And on split:
Logical volume `vg2/lv1` must be inactive.