Using LVM to Manage Disks on Ubuntu

Fri, 17 Jan 2025 00:00:00 +0000

What is LVM

LVM (Logical Volume Manager) is a Linux mechanism for managing disk partitions. It inserts a logical layer between physical disks and file systems, so disk space can be allocated and adjusted more flexibly.

Typical LVM workflow:

Initialize disks as physical volumes (PV)
Combine PVs into a volume group (VG)
Create logical volumes (LV) inside the VG
Create file systems on LVs
Mount and use

With LVM, a file system can span multiple disks and be resized dynamically.

Core LVM Concepts

Physical media: underlying storage devices such as /dev/sda, /dev/nvme0n1.
Physical Volume (PV): a disk/partition initialized for LVM.
Volume Group (VG): a storage pool made of one or more PVs.
Logical Volume (LV): allocatable virtual partition created from a VG.
Physical Extent (PE): fixed-size allocation unit in a VG.
Logical Extent (LE): allocation unit used by an LV (mapped from PE).

Install

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sudo apt update
sudo apt install lvm2

Manage PV

Create PV

pvcreate [option] devname ...

# Example: initialize /dev/sdb and /dev/sdc as PV
pvcreate /dev/sdb /dev/sdc

View PV

pvdisplay [option] devname

# Example
pvdisplay /dev/sdb

Remove PV

pvremove [option] pvname ...

# Example
pvremove /dev/sdb

Manage VG

Create VG

vgcreate [option] vgname pvname ...

# Example: create vg1 with /dev/sdb and /dev/sdc
vgcreate vg1 /dev/sdb /dev/sdc

View VG

vgdisplay [option] [vgname]

# Example
vgdisplay vg1

Extend VG

vgextend [option] vgname pvname ...

# Example
vgextend vg1 /dev/sdb

Reduce VG

vgreduce [option] vgname pvname ...

# Example
vgreduce vg1 /dev/sdb2

Remove VG

vgremove [option] vgname

# Example
vgremove vg1

Manage LV

Create LV

lvcreate [option] vgname

# Example 1: create a 10G LV in vg1
lvcreate -L 10G vg1

# Example 2: create a 200M LV named lv1 in vg1
lvcreate -L 200M -n lv1 vg1

View LV

lvdisplay [option] [lvname]

# Example
lvdisplay /dev/vg1/lv1

Resize LV

lvresize [option] lvname

# Add 200M
lvresize -L +200M /dev/vg1/lv1

# Reduce 200M
lvresize -L -200M /dev/vg1/lv1

# Use all free space in VG
lvresize -l +100%FREE /dev/vg1/lv1

Extend LV

lvextend [option] lvname

# Add 100M
lvextend -L +100M /dev/vg1/lv1

# Use all free space
lvextend -l +100%FREE /dev/vg1/lv1

Reduce LV

lvreduce [option] lvname

# Reduce 100M
lvreduce -L -100M /dev/vg1/lv1

Remove LV

lvremove [option] lvname

# Example
lvremove /dev/vg1/lv1

Create and Mount File System

Create file system

mkfs [option] lvname

# Example: create ext4 on LV
mkfs -t ext4 /dev/vg1/lv1

Mount manually

mount lvname mntpath

# Example
mount /dev/vg1/lv1 /mnt/data

Resize File System After LV Resize

After extending an LV, the file system size does not grow automatically in many cases. For ext4:

# Unmount first (recommended for safety)
umount /dev/vg1/lv1

# Check and repair file system
e2fsck -f /dev/vg1/lv1

# Resize file system to fill LV
resize2fs /dev/vg1/lv1

In some scenarios, online resize is also possible:

`1`	`resize2fs /dev/vg1/lv1`

Logical-Volume-Management on KnightLi Blog