Expanding an LVM volume on Ubuntu without losing data

Düzenlendi · Kapsam: Online LVM2 expansion for ext4 and XFS on Ubuntu 22.04/24.04 LTS.

After enlarging a disk on a cloud server (AWS, GCP or Hetzner), a virtualisation platform (VMware, Proxmox or KVM) or physical hardware, you can make the new capacity available to the filesystem without shutting down the running operating system.

The Linux storage stack with LVM manages storage in layers. Expand them in order from the bottom up:

[ Fiziksel / Sanal Disk: /dev/sda ]
                 │
                 ▼  growpart
[ Disk Bölüntüsü: /dev/sda2 ]
                 │
                 ▼  pvresize
[ LVM Fiziksel Hacmi (PV): /dev/sda2 ]
                 │
                 ▼  (Hacim Grubu - VG otomatik güncellenir)
[ LVM Hacim Grubu (VG): ubuntu-vg ]
                 │
                 ▼  lvextend
[ LVM Mantıksal Hacmi (LV): /dev/ubuntu-vg/ubuntu-lv ]
                 │
                 ▼  resize2fs (ext4) / xfs_growfs (xfs)
[ Dosya Sistemi: / (root) ]

Prerequisites

• Ubuntu 22.04 LTS or 24.04 LTS.
• sudo or root privileges.
• The cloud-guest-utils package, which provides growpart for expanding a partition:

sudo apt-get update
sudo apt-get install -y cloud-guest-utils

1. Inspect the existing storage layout

Identify the filesystem (ext4 or xfs), partition layout and LVM names:

lsblk -o NAME,FSTYPE,SIZE,FSAVAIL,FSUSE%,MOUNTPOINT

Example output:

NAME                      FSTYPE      SIZE FSAVAIL FSUSE% MOUNTPOINT
sda                                   100G                
├─sda1                    vfat        1.1G      1G     4% /boot/efi
└─sda2                    LVM2_member  48G                
  └─ubuntu--vg-ubuntu--lv ext4       46.5G    4.2G    86% /

Here, the main disk (sda) has been enlarged to 100G, while the partition (sda2) and logical volume (ubuntu--vg-ubuntu--lv) are still around 48G.

Check the filesystem type separately:

df -hT /

Expected output:

Filesystem                        Type  Size  Used Avail Use% Mounted on
/dev/mapper/ubuntu--vg-ubuntu--lv ext4   46G   40G  4.2G  91% /

2. Notify the kernel of the new disk size — SCSI rescan

After the disk is enlarged by a hypervisor or cloud provider, the kernel may not detect its new size immediately. Rescan sda:

echo 1 | sudo tee /sys/class/block/sda/device/rescan

To rescan all SCSI buses:

for host in /sys/class/scsi_host/host*/scan; do echo "- - -" | sudo tee "$host"; done

Confirm that lsblk reports the new total size of sda.

3. Expand the partition with growpart

If the LVM physical volume occupies a partition such as /dev/sda2, rather than a raw disk, use growpart to update the partition table.

[!IMPORTANT] Leave a space between the disk device and partition number. Passing /dev/sda2 as a single argument is incorrect.

sudo growpart /dev/sda 2

Expected output:

CHANGED: partition=2 start=2254848 old: size=102602752 end=104857600 new: size=207486943 end=209741791

On GPT disks, the secondary header is stored at the end of the disk. growpart moves this backup header to the new end after expansion.

Check with lsblk that /dev/sda2 now has the larger size.

If LVM uses a whole unpartitioned disk such as /dev/sdb, skip this step and go directly to pvresize /dev/sdb.

4. Update the physical volume with pvresize

After expanding the partition, update LVM’s view of the available capacity:

sudo pvresize /dev/sda2

Expected output:

  Physical volume "/dev/sda2" changed
  1 physical volume(s) resized or updated / 0 physical volume(s) not resized

Check free space in the volume group (VG):

sudo vgs

Expected output:

  VG        #PV #LV #SN Attr   VSize   VFree 
  ubuntu-vg   1   1   0 wz--n- <98.9G <50.0G

The VFree column should show the space available for expansion.

5. Expand the logical volume and filesystem

Using lvextend -r (--resizefs) expands the logical volume and filesystem together.

The -r option invokes fsadm, which detects the filesystem and runs the corresponding resizing tool, reducing the risk of choosing the wrong filesystem-specific command.

To add all free VG capacity to the logical volume:

sudo lvextend -r -l +100%FREE /dev/ubuntu-vg/ubuntu-lv

To add a specific amount, such as 20 GB:

sudo lvextend -r -L +20G /dev/ubuntu-vg/ubuntu-lv

Expected output:

  Size of logical volume ubuntu-vg/ubuntu-lv changed from 46.50 GiB to 96.50 GiB.
  Logical volume ubuntu-vg/ubuntu-lv successfully resized.
resize2fs 1.47.0 (5-Feb-2023)
Filesystem at /dev/mapper/ubuntu--vg-ubuntu--lv is mounted on /; on-line resizing required
old_desc_blocks = 6, new_desc_blocks = 13
The filesystem on /dev/mapper/ubuntu--vg-ubuntu--lv is now 25296896 (4k) blocks long.

6. Manual expansion: ext4 vs XFS

If you ran lvextend -l +100%FREE /dev/ubuntu-vg/ubuntu-lv without -r, expand the filesystem manually. The filesystem type matters.

Manual ext4 expansion

ext4 can grow online while mounted. Pass the block-device path to resize2fs:

sudo resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv

Manual XFS expansion

XFS can also grow online, but xfs_growfs takes the mount point, not the device name:

sudo xfs_growfs /

Growing and shrinking: ext4 and XFS

Result and verification

Finally, verify the filesystem’s size and utilisation:

df -hT /

Expected output:

Filesystem                        Type  Size  Used Avail Use% Mounted on
/dev/mapper/ubuntu--vg-ubuntu--lv ext4   95G   40G   52G  44% /

In this example, capacity was doubled without stopping services or rebooting the server.

Sources and verification environment

• Ubuntu Server LVM documentation
• Linux kernel SCSI rescan documentation (Documentation/scsi/scsi_eh.rst).
• LVM2 lvextend(8), pvresize(8) and growpart(1) manual pages.

These steps were tested and verified in a running Ubuntu 24.04 LTS virtual machine with kernel 6.8, LVM 2.03.16, ext4 and XFS.