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Chapter 10. Virtualized storage devices

10.1. Creating a virtualized floppy disk controller
10.2. Adding storage devices to guests
10.3. Configuring persistent storage in Fedora
10.4. Add a virtualized CD-ROM or DVD device to a guest
This chapter covers installing and configuring storage devices in virtualized guests. The term block devices refers to various forms of storage devices. All the procedures in this chapter work with both Xen and KVM hypervisors.

Valid disk targets

The target variable in libvirt configuration files accepts only the following device names:
  • /dev/xvd[a to z][1 to 15]
    Example: /dev/xvdb13
  • /dev/xvd[a to i][a to z][1 to 15]
    Example: /dev/xvdbz13
  • /dev/sd[a to p][1 to 15]
    Example: /dev/sda1
  • /dev/hd[a to t][1 to 63]
    Example: /dev/hdd3

10.1. 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 should work. 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

This example uses a guest created with virt-manager running a fully virtualized Fedora installation with an image located in /var/lib/libvirt/images/Fedora.img. The Xen hypervisor is used in the example.
  1. Create the XML configuration file for your guest image using the virsh command on a running guest.
    # virsh dumpxml Fedora > 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 31, Creating custom libvirt scripts.
  2. Create a floppy disk image for the guest.
    # dd if=/dev/zero of=/var/lib/libvirt/images/Fedora-floppy.img bs=512 count=2880
  3. Add the content below, changing where appropriate, to your guest's configuration XML file. This example is an emulated floppy device using a file-based image.
    <disk type='file' device='floppy'>
    	<source file='/var/lib/libvirt/images/Fedora-floppy.img'/>
    	<target dev='fda'/>
  4. Force the guest to stop. To shut down the guest gracefully, use the virsh shutdown command instead.
    # virsh destroy Fedora
  5. Restart the guest using the XML configuration file.
    # virsh create Fedora.xml
The floppy device is now available in the guest and stored as an image file on the host.