Linux Logical Volume Management Operations

External

• https://www.howtogeek.com/howto/40702/how-to-manage-and-use-lvm-logical-volume-management-in-ubuntu/

Internal

• Logical Volume Management

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

Physical Volume Concepts

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

• pvcreate - initializes a physical volume(s) for use by LVM.
• pvchange - changes attributes of a physical volume.
• pvresize - resizes a disk or partition in use.
• pvmove - moves physical extents from one physical volume to another.
• pvck - checks the consistency of the physical volume metadata.
• pvremove - removes a physical volume.

Volume Group Operations

Volume Group Concepts

Information about Volume Groups

• vgs - reports information about volume groups.
• vgdisplay - display attributes of volume groups.

Volume Group Management Operations

• vgcreate - create a volume group.
• vgextend - add Physical Volumes to a Volume Group.
• vgreduce - removes one or more unused physical volumes from a volume group.

Logical Volume Operations

Logical Volume

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

• lvcreate - creates a logical volume in an existing volume group.
• lvresize - resize a logical volume.

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