This is a text-only version of the following page on https://raymii.org:
---
Title       :   KVM add disk image or swap image to virtual machine with virsh
Author      :   Remy van Elst
Date        :   23-02-2014
URL         :   https://raymii.org/s/tutorials/KVM_add_disk_image_or_swap_image_to_virtual_machine_with_virsh.html
Format      :   Markdown/HTML
---



This tutorial shows you how to create and add a disk image to a KVM vm using
virsh. This is useful when you for example want to expand the disk space of your
virtual machine when it is using LVM, or if you want to add a swap disk to a
virtual machine. Note that you can also create a swap file instead of a disk,
however, this is an example for adding the disk.

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Read this tutorial to [learn how to set up a proper KVM hypervisor host:
https://raymii.org/s/tutorials/KVM _with_ bonding _and_ VLAN _tagging_ setup
_on_ Ubuntu_12.04.html][2]

### Requirements

 * Host running KVM and virsh

 * Virtual Machine to add disk to

This was tested on a KVM hypervisor host running Ubuntu 12.04 LTS and a Ubuntu
13.10 virtual machine. The KVM hypervisor uses virsh for management.

The example vm is named `example-vm` in virsh (domain).

### Create and attach the disk image

Execute these steps on the KVM hypervisor host.

cd to the folder where you store your disk images:



   cd /var/lib/libvirt/images/


Create the new disk image:



   qemu-img create -f raw example-vm-swap.img 1G


We use `qemu-img` to `create` a new `raw` disk image with a size of 1 GB.

Attach the disk to the example virtual machine using virsh:



   virsh attach-disk example-vm --source /var/lib/libvirt/images/example-vm-swap.img --target vdb --persistent


We use `virsh` to attach the disk image `/var/lib/libvirt/images/example-vm-
swap` as a `virtio` (`/dev/vdb`) disk to the domain (vm) `example-vm`. The
`--persistent` option updates the domain xml file with an element for the newly
attached disk.

Note that if you already have a `/dev/vdb` disk you need to change `vdb` to a
free device like `vdc` or `vdd`.

### Formatting the disk

Execute these steps in your virtual machine.

Reboot it so that the kernel sees the new disk:



   reboot


Partition the drive with `cfdisk`. For our example we use filesystem type 82
(linux/linux swap):



   cfdisk /dev/vdb


Format the disk as swap:



   mkswap /dev/vdb1


Or format it as ext4:



   mkfs.ext4 /dev/vdb1


Make the swap active:



   swapon /dev/vdb1


Or mount the partition:



   mkdir /mnt/new-disk
   mount /dev/vdb1 /mnt/new-disk


Add to /etc/fstab for reboot persistence:



   /dev/vdb1   swap            swap    defaults    0 0


Or for the ext4 disk:



   /dev/vdb1   /mnt/new-disk   ext4    defaults    0 0


That's it. You've now created, attached, formatted and mounted a new disk in
your VM.

### Sources

 * [qemu-img man page][3]
 * [virsh-attach doc page][4]

  [1]: https://www.digitalocean.com/?refcode=7435ae6b8212
  [2]: https://raymii.org/s/tutorials/KVM_with_bonding_and_VLAN_tagging_setup_on_Ubuntu_12.04.html
  [3]: http://linux.die.net/man/1/qemu-img
  [4]: http://builder.virt-tools.org/artifacts/libvirt-virshcmdref/html/sect-attach-disk.html

---

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