Logical Volume Management (lvm) Guide

Logical Volume Management (LVM) provides a flexible way to manage disk space. It allows you to create virtual partitions that can be easily resized, even across multiple physical drives.

Physical Volumes (pv)

Physical volumes are the raw building blocks (partitions or full disks) that LVM uses.

Create a Physical Volume

Initialize a partition or disk for LVM use.

pvcreate /dev/nvme1n1p1

Display Physical Volumes

Check the status and capacity of your physical volumes.

# Brief summary
pvs

# Detailed information
pvdisplay

Volume Groups (vg)

A Volume Group is a pool of storage created by combining one or more Physical Volumes.

Create a Volume Group

Combine multiple physical partitions into a single pool named myvg.

vgcreate myvg /dev/nvme1n1p1 /dev/nvme1n1p2

Display Volume Groups

# Brief summary
vgs

# Detailed information
vgdisplay

Logical Volumes (lv)

Logical Volumes are the "virtual partitions" created from a Volume Group. You format these with a filesystem and mount them.

Create a Logical Volume

Create a volume named mylvm with a size of 2GB.

# -L: size (e.g., 2G, 500M)
# -n: name of the logical volume
lvcreate -L 2G -n mylvm myvg

Format the Volume

Before using the volume, create a filesystem (e.g., ext4).

mkfs.ext4 /dev/myvg/mylvm

Mount the Volume

Map the volume to a directory in your system.

# Check block devices
lsblk

# Create mount point and mount
mkdir /data
mount /dev/myvg/mylvm /data/

Extending Storage

One of the main benefits of LVM is the ability to grow storage on the fly.

Step A: Prepare New Physical Storage

If you run out of space in the Volume Group, initialize a new partition.

pvcreate /dev/nvme1n1p3

Step B: Extend the Volume Group

Add the new physical volume to your existing pool.

vgextend myvg /dev/nvme1n1p3

Step C: Extend the Logical Volume

Increase the size of the logical volume.

# Add 2GB to the current size
lvextend -L +2G /dev/myvg/mylvm

Step D: Resize the Filesystem

The LV is now larger, but the filesystem (ext4) needs to be told to fill that new space.

# Check for errors first
e2fsck -f /dev/myvg/mylvm

# Resize to fill the new LV capacity
resize2fs /dev/myvg/mylvm

Shrinking Storage

Warning: Shrinking a volume is risky. Always back up your data first. You must shrink the filesystem before reducing the Logical Volume size.

Step A: Unmount the Volume

You cannot safely shrink most filesystems while they are mounted.

umount /data

Step B: Check and Resize Filesystem

Reduce the filesystem to the target size (e.g., 2GB).

e2fsck -f /dev/myvg/mylvm
resize2fs /dev/myvg/mylvm 2G

Step C: Reduce the Logical Volume

Now that the filesystem is small, you can reduce the LV container.

lvreduce -L 2G /dev/myvg/mylvm

Step D: Re-mount and Verify

mount /dev/myvg/mylvm /data/
df -h /data

Summary of Useful Commands