LVM(Logical Volume Manager) introduction

LVM(Logical Volume Manager) is a useful tool in linux to manage the disk volume. The main purpose is to dynamically manage the disks in linux. You can use LVM to extend or shrink the disks in OS without rebooting.

Key components:

Physical volume (PV): Partition on hard disk (or even hard disk itself or loopback file) on which you can have volume groups

Volume group (VG): Group of physical volumes that are used as storage volume.

Logical volume (LV): A "virtual/logical partition" that resides in a volume group, it can be used to as a traditional partition and mounted to the mount point.

The picture is from internet.

0. Create a partition using fdisk. 

(this is omitted as not related with LVM), but make sure it’s type set to Linux LVM (8e)

   1. Create PV from disk partition:

commands: pvcreate [device partition]

 

2. Create the VG.

Then you need to create the volume group using the PV.

Commands:

vgcreate [volume ground name] PV        //create the new VG

vgcreate [volume ground name] PV        //add the PV to new VG

eg:

vgcreate newvg /dev/sdb1

vgextend newvg /dev/sdc1

3. Create the logic volume (LV) from VG.

Commands:

#lvcreate –L size [VG] –n [LVname]

 4. view the device 

Now you can view the device by

#ls –l /dev/mapper/[VG]-[LV]

#ls –l /dev/[VG]/[LV]

   5. Make file system and mount the files

mkfs.[filesystem format] [LV]

mount [LV] [mount-point]

   

6. Extend the LV size (expand the file system capacity as well)

Commands:

Lvextend –L [size] [lv]

Resize2fs [lv]

Eg:

lvextend -L 200m /dev/newvg/lvhome

resize2fs /dev/newvg/lvhome

This is the basic usage of LVM, there are other advanced usages such as shrink, remove PV, snapshots, you can refer to other online documents.