Linux Logical Volume Management Operations

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External

Internal

Overview

Logical volume management commands can be issued from the lvm console, or as standalone commands. For example: 

lvm> lvs

produces identical results to 

lvs

Inventory of Devices that May Be Used as Physical Volumes

lvmdiskscan

Example: 

[root@rhel-test ~]# lvmdiskscan
  /dev/rhel_rhel-test/swap [     820.00 MiB] 
  /dev/sda1                [     500.00 MiB] 
  /dev/rhel_rhel-test/root [       6.67 GiB] 
  /dev/sda2                [       7.51 GiB] LVM physical volume
  /dev/sdb                 [       2.00 GiB] 
  3 disks
  1 partition
  0 LVM physical volume whole disks
  1 LVM physical volume

The output specifies which device is already a LVM Physical Volume

To see only the existing Physical Volumes (devices that have Volume Groups on them) 

lvmdiskscan -l

Physical Volume Operations

Information about Physical Volumes

  • pvs - provides information about physical volumes available on the system.
  • pvscan - scans all disks for physical volumes.
  • pvdisplay - provides details about a specific physical volume.

Physical Volume Management Operations

  • Change attributes of physical volume
pvchange
  • Resize physical volume
pvresize
  • Check the consistency of physical volume
pvck
  • Move extents from one physical volume to another
pvmove
  • Remove LVM label(s) from physical volume(s)
pvremove

Volume Group Operations

Information about Volume Groups

vgs
vgdisplay --verbose

Volume Group Management Operations

Logical Volume Operations

Information about Logical Volumes

  • lvs - provides information about logical volumes available on the system.
  • lvdisplay - displays attributes of a logical volume.
  • lvscan - scans all known volume groups or all supported LVM block devices in the system for defined Logical Volumes.

Logical Volume Management Operations

Creating a Logical Volume

lvm
lvm> lvcreate --size 20G --name santorini VolGroup00

Extending a Logical Volume

http://www.azhowto.com/2009/02/06/how-to-resize-lvm-running-xen-explained-part-1-increase-disk-size

Renaming a Logical Volume

lvm 
lvm> lvrename VolGroup00 LogVol05numbercat lv05


Remove a Logical Volume

Gather statistics on the free space before removing, and also on the size of the logical volume to be removed: 

vgs

lvs

Unmount the volume if necessary (or shutdown the service that is using it, as it is the case with Docker): 

umount /dev/VolGroup00/MyLV1

Remove the logical volume with lvremove.

The command has a "dry run mode" (-t): 

lvremove /dev/<VG_name>/<LV_name>

lvremove -t /dev/<VG_name>/<LV_name>

Example: 

[root@rhel-test lvm]# lvremove -t /dev/rhel_rhel-test/docker-pool 
  TEST MODE: Metadata will NOT be updated and volumes will not be (de)activated.
Do you really want to remove active logical volume docker-pool? [y/n]: y
  Logical volume "docker-pool" successfully removed

This command actually removes it: 

lvremove [-v] /dev/VolGroup00/MyLV1

Shrinking the Filesystem and the Logical Volume

This is the simple case, it will only work if the logical volume *does not* contain a partition table: 

fsadm

or 

umount lvm_partition
resize2fs /dev/vg/lv newSize
lvresize -L disksize /dev/vg/lv
resize2fs /dev/vg/lv

Shrinking a Logical Volume used by a xen Virtual Machine

Logical Volume Management and Virtualization
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