Linux LVM

Logical Volume Manager (LVM) is an advanced storage management feature that offers more flexibility than traditional disk partitioning. A key advantage of LVM is the ability to easily resize logical volumes, which was difficult with traditional partitions.

I personally use LVM to partition my / and /home into two separate logical volumes.

Key Concepts

There are 3 concepts that LVM manages, organized in a hierarchy:

• Physical volumes: lowest-level of building block
• Volume groups: are collections of physical volumes. This abstraction is useful if we have multiple disks and we want to combine them into a single group
• Logical volumes: created from volume groups, analogous to partitions

Physical Volumes

A physical volume can either be a raw disk or a disk partition. All commands that manage physical volumes start with the letters pv.

Create Physical Volumes

sudo pvcreate /dev/sda1

Listing Physical Volumes

We have several different commands with varying levels of verbosity: pvscan, pvs, and pvdisplay

Remove a Physical Volume

sudo pvremove /dev/sda1

Volume Groups

Volume group commands start with vg.

Create Volume Group

sudo vgcreate vg /dev/sda1 /dev/sda2

Listing Volume Groups

vgdisplay, vgscan and vgs

Add Additional Physical Volumes to a Volume Group

Syntax:

vgextend <volume_group> <physical_volume1> <physical_volume2> ....

Example:

sudo vgextend vg /dev/sda3

Note that if /dev/sda3 is not a physical volume, vgextend will automatically make it one.

Remove Physical Volumes from a Volume Group

sudo vgreduce vg /dev/sda1 /dev/sda2

Removing a Volume Group

sudo vgremove vg

Logical Volumes

All logical volume commands start with lv

Create Logical Volumes

Syntax:

sudo lvcreate -L <size> -n <lvname> <vgname>

Example:

sudo lvcreate -L 5GB -n lv1 vg

We can also create a logical volumes that use all the space in the volume group with the following syntax:

sudo lvcreate -l 100%FREE -n <lvname> <vgname>

Operations on Logical Volumes

After creating logical volumes, we need to give them filesystems. For example:

sudo mkfs.ext4 /dev/vg/lv1

We can also mount it:

sudo mount -t ext4 /dev/vg/lv1 /mnt

Resizing a Logical Volume

There are lvextend and lvreduce commands to increase or decrease the size of a logical volume. And there is also a lvresize that can accomplish both:

sudo lvresize -L -2GB vg/lv1

Removing a Logical Volume

Finally, we can remove a logical volume with lvremove:

sudo lvremove vg/lv1