Installation guide

Chapter 27. Volumes

238

27.3. Adding storage devices to guests

This section covers adding storage devices to a virtualized guest. Additional storage can only be

added after guests are created.

27.3.1. Adding file based storage to a guest

File-based storage or file-based containers are files on the hosts file system which act as virtualized

hard drives for virtualized guests. To add a file-based container perform the following steps:

1. Create an empty container file or using an existing file container (such as an ISO file).

a. Create a sparse file using the dd command. Sparse files are not recommended due to data

integrity and performance issues. Sparse files are created much faster and can used for

testing but should not be used in production environments.

# dd if=/dev/zero of=/var/lib/libvirt/images/FileName.img bs=1M seek=4096 count=0

b. Non-sparse, pre-allocated files are recommended for file-based storage images. Create a

non-sparse file, execute:

# dd if=/dev/zero of=/var/lib/libvirt/images/FileName.img bs=1M count=4096

Both commands create a 400MB file which can be used as additional storage for a virtualized

guest.

2. Dump the configuration for the guest. In this example the guest is called Guest1 and the file is

saved in the users home directory.

# virsh dumpxml Guest1 > ~/Guest1.xml

3. Open the configuration file (Guest1.xml in this example) in a text editor. Find the <disk>

elements, these elements describe storage devices. The following is an example disk element:

</disk>

4. Add the additional storage by duplicating or writing a new <disk> element. Ensure you specify

a device name for the virtual block device attributes. These attributes must be unique for each

guest configuration file. The following example is a configuration file section which contains an

additional file-based storage container named FileName.img.

</disk>