27.3.2. Adding hard drives and other block devices to a guest
System administrators use additional hard drives to provide increased storage space for a guest, or to separate system data from user data.
Procedure 27.1. Adding physical block devices to virtualized guests
This procedure describes how to add a hard drive on the host to a virtualized guest. It applies to all physical block devices, including CD-ROM, DVD and floppy devices.
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Physically attach the hard disk device to the host. Configure the host if the drive is not accessible by default.
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Configure the device with multipath
and persistence on the host if required.
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Use the virsh attach
command as below, replacing:
# virsh attach-disk myguest
/dev/sdb1
sdc
--driver tap --mode readonly
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myguest
with the name of the guest.
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/dev/sdb1
with the device on the host to add.
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sdc
with the location on the guest where the device should be added. It must be an unused device name.
Use the sd*
notation for Windows guests as well, the guest will recognize the device correctly.
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Only include the --mode readonly
parameter if the device should be read only to the guest.
Additionally, there are optional arguments that may be added:
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The guest now has a new hard disk device called /dev/sdb
on Linux or D: drive
, or similar, on Windows. This device may require formatting.
The host should not use disk labels to identify file systems in the fstab
file, the initrd
file or on the kernel command line. Doing so presents a security risk if less privileged users, such as virtualized guests, have write access to whole partitions or LVM volumes.
A virtualized guest could write a disk label belonging to the host, to its own block device storage. Upon reboot of the host, the host could then mistakenly use the virtualized guests disk as a system disk, compromising the host system.