The first step in implementing LVM is to create physical volumes. In addition to creating physical volumes, commands exist to display the attributes of physical volumes, remove physical volumes, and perform other functions on physical volumes.
Creating Physical Volumes
Use the pvcreate command to create physical volumes. The syntax is:
# pvcreate [options] device
You can initialize multiple disks or partitions for use by LVM in the same command. For example, the following command initializes two disks (you can also use disk partitions here). The –v option makes the output more verbose:
# pvcreate -v /dev/sdb /dev/sdc
Wiping internal VG cache
Wiping cache of LVM-capable devices
Wiping signatures on new PV /dev/sdb.
Wiping signatures on new PV /dev/sdc.
Set up physical volume for "/dev/sdb" with 41943040 available sectors.
Zeroing start of device /dev/sdb.
Writing physical volume data to disk "/dev/sdb".
Physical volume "/dev/sdb" successfully created.
Set up physical volume for "/dev/sdc" with 41943040 available sectors.
Zeroing start of device /dev/sdc.
Writing physical volume data to disk "/dev/sdc".
Physical volume "/dev/sdc" successfully created. Displaying Physical Volumes
Use the pvdisplay command to display attributes of physical volumes.
v# pvdisplay ... --- NEW Physical volume --- PV Name /dev/sdb VG Name PV Size 20.00 GiB Allocatable NO PE Size 0 Total PE 0 Free PE 0 Allocated PE 0 PV UUID cqd7sN-0cSk-NGT5-cd9c-1Efk-vbKS-v1Bkha
In addition to pvdisplay, two other commands list information about physical volumes. The pvs command reports information about physical volumes in a more condensed form. The pvscan command scans all disks for physical volumes. Example:
# pvs PV VG Fmt Attr PSize PFree /dev/sda2 cl lvm2 a-- 19.00g 0 /dev/sdb lvm2 --- 20.00g 20.00g /dev/sdc lvm2 --- 20.00g 20.00g
# pvscan PV /dev/sda2 VG cl lvm2 [19.00 GiB / 0 free] PV /dev/sdc lvm2 [20.00 GiB] PV /dev/sdb lvm2 [20.00 GiB] Total: 3 [59.00 GiB] / in use: 1 [19.00 GiB] / in no VG: 2 [40.00 GiB]
Removing Physical Volumes
Use the pvremove command to remove a physical volume, for example:
# pvremove /dev/sdc Labels on physical volume "/dev/sdc" successfully wiped.
# pvdisplay /dev/sdc Failed to find physical volume "/dev/sdc".
Additional PV Commands
The following are other commands that are associated with the manipulation of physical volumes:
- pvchange: Change the attributes of physical volumes.
- pvresize: Resize physical volumes.
- pvck: Check the consistency of physical volumes.
- pvmove: Move extents from one physical volume to another.