LVM (Logical Volume Manager) puts a flexible layer between your disks and your filesystems, so you can grow a volume without repartitioning or unmounting it. In this tutorial you will inspect an LVM setup and extend a logical volume and its filesystem online on Ubuntu 24.04 in the three situations you will actually meet: the volume group already has free space, the underlying disk has been enlarged, or you add a new disk.

Prerequisites

To follow this guide you need:

  • A server running Ubuntu 24.04 LTS that uses LVM, with a non-root user that has sudo privileges. Ubuntu Server installs from the ISO use LVM by default; many cloud images do not. Step 1 shows how to check.
  • A recent backup of the data on the volume. Growing a volume is a safe, routine operation, but a typo in a device name is not.
  • Console access to the server is recommended if you are working on the root volume.

How LVM is organized

LVM has three layers. You grow them from the bottom up:

LayerCommand to inspectWhat it is
Physical volume (PV)pvsA disk or partition prepared for LVM, for example /dev/sda3
Volume group (VG)vgsA pool of space made from one or more PVs, for example ubuntu-vg
Logical volume (LV)lvsA slice of the VG that holds a filesystem, for example ubuntu-lv mounted on /

A logical volume can only grow into free space in its volume group. The volume group only grows when a physical volume grows or a new one is added.

Step 1 - Inspecting the current layout

First, check whether the filesystem you want to extend sits on LVM:

df -hT /

Filesystem                        Type  Size  Used Avail Use% Mounted on
/dev/mapper/ubuntu--vg-ubuntu--lv ext4   48G   41G  4.9G  90% /

A /dev/mapper/... device means LVM. If you see /dev/vda1 or /dev/sda1 instead, the filesystem is on a plain partition and you only need growpart and resize2fs, not this guide.

Show the whole storage tree:

lsblk

NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda                         8:0    0  100G  0 disk
├─sda1                      8:1    0    1M  0 part
├─sda2                      8:2    0    2G  0 part /boot
└─sda3                      8:3    0   98G  0 part
  └─ubuntu--vg-ubuntu--lv 252:0    0   49G  0 lvm  /

Then look at each LVM layer:

sudo pvs
sudo vgs
sudo lvs

  PV         VG        Fmt  Attr PSize   PFree
  /dev/sda3  ubuntu-vg lvm2 a--  <98.00g <49.00g
  VG        #PV #LV #SN Attr   VSize   VFree
  ubuntu-vg   1   1   0 wz--n- <98.00g <49.00g
  LV        VG        Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  ubuntu-lv ubuntu-vg -wi-ao---- <49.00g

The VFree column tells you which step applies:

  • VFree is greater than zero: the space is already in the volume group. Go to Step 2.
  • The disk is bigger than its partitions (for example, lsblk shows sda at 150G but sda3 at 98G): go to Step 3.
  • You attached a new disk: go to Step 4.

The output above is a very common case: the Ubuntu Server installer only allocates part of the volume group to ubuntu-lv and leaves the rest free.

Step 2 - Extending a volume using free space in the volume group

Use lvextend with -l +100%FREE to give the logical volume all the free space in its group, and -r (--resizefs) to grow the filesystem in the same command. -r detects whether the filesystem is ext4 or XFS and calls the right tool, and both can be grown while mounted:

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

  Size of logical volume ubuntu-vg/ubuntu-lv changed from <49.00 GiB (12543 extents) to <98.00 GiB (25087 extents).
  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 = 7, new_desc_blocks = 13
The filesystem on /dev/mapper/ubuntu--vg-ubuntu--lv is now 25689088 (4k) blocks long.

To add a fixed amount instead of all the free space, use -L, for example sudo lvextend -r -L +20G /dev/ubuntu-vg/ubuntu-lv. Keeping some free space in the volume group is useful if you have several logical volumes or plan to use LVM snapshots.

Verify the new size:

df -h /
sudo vgs

Filesystem                         Size  Used Avail Use% Mounted on
/dev/mapper/ubuntu--vg-ubuntu--lv   97G   41G   52G  45% /
  VG        #PV #LV #SN Attr   VSize   VFree
  ubuntu-vg   1   1   0 wz--n- <98.00g    0

Step 3 - Extending after the disk has been enlarged

When the virtual disk behind the server gets bigger, for example after moving to a larger plan, LVM does not see the extra space until you grow the partition and then the physical volume.

Making the kernel see the new disk size

Check the disk size with lsblk. On virtio disks (vda) the new size usually appears on its own. On SCSI or SATA disks (sda), ask the kernel to rescan the device:

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

NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda                         8:0    0  150G  0 disk
├─sda1                      8:1    0    1M  0 part
├─sda2                      8:2    0    2G  0 part /boot
└─sda3                      8:3    0   98G  0 part
  └─ubuntu--vg-ubuntu--lv 252:0    0   98G  0 lvm  /

The disk is now 150G, but sda3 is still 98G.

Growing the partition

growpart extends a partition to the end of the disk while it is in use. It comes with the cloud-guest-utils package:

sudo apt install cloud-guest-utils
sudo growpart /dev/sda 3

CHANGED: partition=3 start=4198400 old: size=205516767 end=209715166 new: size=310374367 end=314572766

The partition number is a separate argument: /dev/sda 3, not /dev/sda3. growpart only works on the last partition of the disk.

Growing the physical volume and the logical volume

Tell LVM that the physical volume is now bigger:

sudo pvresize /dev/sda3

  Physical volume "/dev/sda3" changed
  1 physical volume(s) resized or updated / 0 physical volume(s) not resized

The new space is now free in the volume group. Check it and extend the logical volume exactly as in Step 2:

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

Filesystem                         Size  Used Avail Use% Mounted on
/dev/mapper/ubuntu--vg-ubuntu--lv  146G   41G   99G  30% /

Step 4 - Extending by adding a new disk

If you cannot enlarge the existing disk, add a second one to the volume group. Identify it first; it should have no partitions and no mount point:

lsblk

NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda                         8:0    0  100G  0 disk
├─sda1                      8:1    0    1M  0 part
├─sda2                      8:2    0    2G  0 part /boot
└─sda3                      8:3    0   98G  0 part
  └─ubuntu--vg-ubuntu--lv 252:0    0   98G  0 lvm  /
sdb                         8:16   0   50G  0 disk

Initialize the whole disk as a physical volume:

sudo pvcreate /dev/sdb

  Physical volume "/dev/sdb" successfully created.

Add it to the volume group:

sudo vgextend ubuntu-vg /dev/sdb

  Volume group "ubuntu-vg" successfully extended

Confirm the group has two physical volumes and new free space, then extend the logical volume:

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

  VG        #PV #LV #SN Attr   VSize   VFree
  ubuntu-vg   2   1   0 wz--n- 147.99g <50.00g

After this, the logical volume spans both disks. Losing either disk damages the whole volume, so on a production server put the extra space on redundant storage (for example a RAID 1 array created with mdadm) or make sure your backups are current.

Step 5 - Verifying the result

Check each layer and the filesystem:

sudo pvs
sudo vgs
sudo lvs
df -hT /

If you extended the volume without -r, the logical volume is bigger but the filesystem is not. df shows the old size in that case. Grow the filesystem by hand:

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

For XFS, pass the mount point instead of the device:

sudo xfs_growfs /

Troubleshooting

Insufficient free space: ... extents needed, but only 0 available. The volume group has no free space. Follow Step 3 or Step 4 to add space to the group first.

df still shows the old size after lvextend. The filesystem was not resized. Run resize2fs (ext4) or xfs_growfs (XFS) as shown in Step 5.

pvresize reports no change. The partition was not grown or the kernel still sees the old size. Check lsblk; run the rescan and growpart from Step 3, then pvresize again.

NOCHANGE: partition 3 is size ... it cannot be grown. The disk has not grown from the kernel's point of view, or the LVM partition is not the last one on the disk. Rescan the disk, and if another partition sits after it, add a new partition or disk as a separate physical volume instead.

You want to make a volume smaller. ext4 can be shrunk only while unmounted (lvreduce -r handles it) and XFS cannot be shrunk at all. Plan sizes with room to grow instead of allocating everything up front.

Conclusion

You inspected the PV, VG and LV layers and extended a logical volume and its filesystem online using free space, a grown disk and a new disk. As next steps, create separate logical volumes for data such as /var/lib/mysql from the remaining free space, try LVM snapshots (lvcreate -s) before risky upgrades, and set up disk usage alerts so you extend volumes before they fill up.