A virtual machine's disk may have to be resized, typically due to lack of space. This page explains how to do so.
In-place expansion is not supported. A new disk of the desired size has to be created.
cd /var/lib/libvirt/images
Use the following command to create a disk of 20 GB called guest_20G.img.
qemu-img create -f raw guest_20G.img 20G
guest.img# virt-filesystems -a -l -h guest.img
Name Type VFS Label Size Parent
/dev/vda1 filesystem vfat EFI 133935104 -
/dev/vda2 filesystem ext4 boot 366869504 -
/dev/vda3 filesystem ext4 root 9933475840 -
One can tell that the root partition is located under /dev/vda3. This is the one that will need to be expanded.
This command is cabable of expanding different kinds of filesystems, including
ext4andbtrfs
# virt-resize --expand /dev/vda3 guest.img guest_20G.img
[ 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.
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.
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."
On Fedora-related distributions, virt-resize is provided by the guestfs-tools package :
# dnf install guestfs-tools