4.2. Physical Volume Administration

This section describes the commands that perform the various aspects of physical volume administration.

4.2.1. Creating Physical Volumes

The following subsections describe the commands used for creating physical volumes.

4.2.1.1. Setting the Partition Type

If you are using a whole disk device for your physical volume, the disk must have no partition table. For DOS disk partitions, the partition id should be set to 0x8e using the fdisk or cfdisk command or an equivalent. For whole disk devices only the partition table must be erased, which will effectively destroy all data on that disk. You can remove an existing partition table by zeroing the first sector with the following command:

dd if=/dev/zero of=PhysicalVolume bs=512 count=1

4.2.1.2. Initializing Physical Volumes

Use the pvcreate command to initialize a block device to be used as a physical volume. Initialization is analogous to formatting a file system.

The following command initializes /dev/sdd1, /dev/sde1, and /dev/sdf1 for use as LVM physical volumes.

pvcreate /dev/sdd1 /dev/sde1 /dev/sdf1

To initialize partitions rather than whole disks: run the pvcreate command on the partition. The following example initializes the partition /dev/hdb1 as an LVM physical volume for later use as part of an LVM logical volume.

pvcreate /dev/hdb1

4.2.1.3. Scanning for Block Devices

You can scan for block devices that may be used as physical volumes with the lvmdiskscan command, as shown in the following example.

# lvmdiskscan
/dev/ram0                    [       16.00 MB]
  /dev/sda                     [       17.15 GB]
  /dev/root                    [       13.69 GB]
  /dev/ram                     [       16.00 MB]
  /dev/sda1                    [       17.14 GB] LVM physical volume
  /dev/VolGroup00/LogVol01     [      512.00 MB]
  /dev/ram2                    [       16.00 MB]
  /dev/new_vg/lvol0            [       52.00 MB]
  /dev/ram3                    [       16.00 MB]
  /dev/pkl_new_vg/sparkie_lv   [        7.14 GB]
  /dev/ram4                    [       16.00 MB]
  /dev/ram5                    [       16.00 MB]
  /dev/ram6                    [       16.00 MB]
  /dev/ram7                    [       16.00 MB]
  /dev/ram8                    [       16.00 MB]
  /dev/ram9                    [       16.00 MB]
  /dev/ram10                   [       16.00 MB]
  /dev/ram11                   [       16.00 MB]
  /dev/ram12                   [       16.00 MB]
  /dev/ram13                   [       16.00 MB]
  /dev/ram14                   [       16.00 MB]
  /dev/ram15                   [       16.00 MB]
  /dev/sdb                     [       17.15 GB]
  /dev/sdb1                    [       17.14 GB] LVM physical volume
  /dev/sdc                     [       17.15 GB]
  /dev/sdc1                    [       17.14 GB] LVM physical volume
  /dev/sdd                     [       17.15 GB]
  /dev/sdd1                    [       17.14 GB] LVM physical volume
  7 disks
  17 partitions
  0 LVM physical volume whole disks
  4 LVM physical volumes