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Accessing data from a guest disk image

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28.3. Accessing data from a guest disk image

There are various methods for accessing the data from guest image files. One common method is to

use the kpartx tool, covered by this section, to mount the guest file system as a loop device which

can then be accessed.

The kpartx command creates device maps from partition tables. Each guest storage image has a

partition table embedded in the file.

The li/jointfilesconvert/340954/bguestfs and guestfish packages, available from the EPEL

repository, allow advanced

modification and access to guest file systems. The li/jointfilesconvert/340954/bguestfs and guestfish packages are not covered

in this section at this time.

Warning

Guests must be offline before their files can be read. Editing or reading files of an active guest is

not possible and may cause data loss or damage.

Procedure 28.1. Accessing guest image data

1. Install the kpartx package.

# yum install kpartx

2. Use kpartx to list partition device mappings attached to a file-based storage image. This example

uses a image file named guest1.img.

# kpartx -l /var/lib/libvirt/images/guest1.img

loop0p1 : 0 409600 /dev/loop0 63

loop0p2 : 0 10064717 /dev/loop0 409663

guest1 is a Linux guest. The first partition is the boot partition and the second partition is an

EXT3 containing the root partition.

3. Add the partition mappings to the recognized devices in /dev/mapper/.

# kpartx -a /var/lib/libvirt/images/guest1.img

• Test that the partition mapping worked. There should be new devices in the /dev/mapper/

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Red Hat ENTERPRISE LINUX 5 - VIRTUALIZATION GUIDE Guida di Installazione Pagina 257