Chapter 4. Virtualized block devices

4.1. Creating a virtualized floppy disk controller
4.2. Adding storage devices to guests
4.3. Configuring persistent storage
4.4. Add a virtualized CD-ROM or DVD device to a guest

This chapter covers installing and configuring block devices in virtualized guests. The term block devices refers to various forms of storage devices.

4.1. Creating a virtualized floppy disk controller

Floppy disk controllers are required for a number of older operating systems, especially for installing drivers. Presently, physical floppy disk devices cannot be accessed from virtualized guests. However, creating and accessing floppy disk images from virtualized floppy drives is supported. This section covers creating a virtualized floppy device.

An image file of a floppy disk is required. Create floppy disk image files with the dd command. Replace /dev/fd0 with the name of a floppy device and name the disk appropriately.

# dd if=/dev/fd0 of=~/legacydrivers.img

Para-virtualized drivers note

The para-virtualized drivers can map physical floppy devices to fully virtualized guests.

This example uses a guest created with virt-manager running a fully virtualized Linux installation with an image located in /var/lib/libvirt/images/rhel5FV.img. The Xen hypervisor is used in the example.

Create the XML configuration file for your guest image using the virsh command on a running guest.
```
# virsh dumpxml rhel5FV > rhel5FV.xml
```
This saves the configuration settings as an XML file which can be edited to customize the operations and devices used by the guest. For more information on using the virsh XML configuration files, refer to Chapter 18, Creating custom libvirt scripts.

Create a floppy disk image for the guest.

# dd if=/dev/zero of=/var/lib/libvirt/images/rhel5FV-floppy.img bs=512 count=2880

Add the content below, changing where appropriate, to your guest's configuration XML file. This example creates a guest with a floppy device as a file based virtual device.
```
<disk type='file' device='floppy'>
	<source file='/var/lib/libvirt/images/rhel5FV-floppy.img'/>
	<target dev='fda'/>
</disk>
```
Stop the guest.
```
# virsh stop rhel5FV
```
Restart the guest using the XML configuration file.
```
# virsh create rhel5FV.xml
```

The floppy device is now available in the guest and stored as an image file on the host.