wiki/gofurther/resize.md

title, description, published, date, tags, editor, dateCreated

title	description	published	date	tags	editor	dateCreated
Resize an existing virtual disk		true	2026-05-08T09:34:59.946Z		markdown	2021-11-13T11:41:29.087Z

Resize a virtual disk

Background

A virtual machine's disk may have to be resized, typically due to lack of space. This page explains how to do so.

Preparation

Shut down virtual machine

Please ensure that the virtual machine using the virtual disk to be resized is turned off {.is-warning}

Let's assume that you wish to increase the size of the virtual machine called guest.

• List virtual machines running on your host

# virsh list --all

Id   Name                                State
----------------------------------------------------
 1    guest                              running

• Shutdown the guest virtual machine

# virsh shutdown guest

• Ensure that the virtual machine is fully shut off

# virsh list --all

Id   Name                                State
----------------------------------------------------
 1    guest                              shut off

It is now safe to proceed to the next step

Backup existing disk

It is advisable to make a backup first.

• Navigate to the correct directory

# cd /var/lib/libvirt/images

• Make a copy of the virtual disk image

# cp guest.img backup_guest.img

Linux guests

In-place expansion is not supported. A new disk of the desired size has to be created, and then swap with the former disk. {.is-info}

• Navigate to the location that contains the existing image

# cd /var/lib/libvirt/images

• Create a new blank 20 GB disk called guest_20G.img

# qemu-img create -f raw guest_20G.img 20G

• Identify the filesystem layout of the existing disk guest.img, which is ext4-based

# virt-filesystems -a guest.img -l -h
Name       Type        VFS   Label  Size        Parent
/dev/vda1  filesystem  vfat  EFI    1.3G        -
/dev/vda2  filesystem  ext4  boot   3.6G        -
/dev/vda3  filesystem  ext4  root   10G         -

• Another output for a btrfs-based filesystem

# virt-filesystems -a bazzite-desktop.img -l -h
Name                    Type       VFS   Label         Size Parent
/dev/sda1               filesystem vfat  -             599M -
/dev/sda2               filesystem ext4  bazzite_xboot 1.9G -
/dev/sda3               filesystem btrfs bazzite       37G  -
btrfsvol:/dev/sda3/root filesystem btrfs bazzite       -    -
btrfsvol:/dev/sda3/home filesystem btrfs bazzite       -    -
btrfsvol:/dev/sda3/var  filesystem btrfs bazzite       -    -

Thanks to the label on the ext4-based based image, one can tell that the root partition is /dev/vda3. This is the one that will need to be expanded. For the btrfs example, the root partition /dev/sda3as shown by btrfsvol:/dev/sda3/root

• Copy the former old data to the new disk and expand the root partition of the said disk

This command is capable of expanding different kinds of filesystems, including ext4 and btrfs
{.is-info}

The command takes the new empty disk as last argument.

Data could be erased if you mix argument! {.is-warning}

# virt-resize --expand /dev/vda3 guest.img guest_20G.img

• Review changes

[   0.0] Examining guest_20G.img
**********

Summary of changes:

/dev/vda1: This partition will be left alone.

/dev/vda2: This partition will be left alone.

/dev/vda3: This partition will be resized from 10G to 20G.  The 
filesystem ext4 on /dev/vda3 will be expanded using the ‘resize2fs’ 
method.

**********
[   2.1] Setting up initial partition table on guest_20G.img
[  12.9] Copying /dev/vda1
[  13.1] Copying /dev/vda2
[  13.4] Copying /dev/vda3
 100% ⟦▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒⟧ 00:00
[  38.3] Expanding /dev/vda3 using the ‘resize2fs’ method

Resize operation completed with no errors.  Before deleting the old disk, 
carefully check that the resized disk boots and works correctly.

• Switch to the new disk for your virtual machine

Now that the new disk has been created, it can be used in the virtual machine.

# virsh edit guest

Locate the source line for the existing disk guest.img:

[...]
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writeback' discard='unmap'/>
      <source file='/var/lib/libvirt/images/guest.img'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
    </disk>
[...]

Edit the said line so that it points to the new disk guest-20G.img:

[...]
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writeback' discard='unmap'/>
      <source file='/var/lib/libvirt/images/guest-20G.img'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
    </disk>
[...]

Start the virtual machine and ensure that it is working properly. If it does, the former disk could be removed.

Resources

As per the software description : "qemu-img allows you to create, convert and modify images offline. It can handle all image formats supported by QEMU."

• Installation

On Fedora-related distributions, virt-resize is provided by the guestfs-tools package :

# dnf install guestfs-tools

---

Go to parent page