XEN: How to CD-boot fully-virtualized DomU's after initial installation

This document (3156432) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Desktop 10 SP1

SUSE Linux Enterprise Server 10 SP1

Situation

After the initial installation, a DomU needs to be booted from CD.

Resolution

Booting to a CD after installing a fully virtualized DomU is straight forward and simple, more so than para-virtualized DomU's. This method can be used to boot a SuSE Linux Enterprise 9 or 10 computer into a rescue system.

For the purposes of this TID, replace SLES10 with the name of your DomU. The "hda" is a hard-drive, "hdc" is a CD-ROM device that uses an ISO image.

Shutdown the DomU guest
Go to /etc/xen/vm
Locate the configuration file for the DomU
Copy the configuration file; the copy will be used instead of the original file
cp /etc/xen/vm/sles10 /etc/xen/vm/sles10-cdboot
Open the file for editing
Change the name of the DomU in the configuration file. This can be done by locating the name="..." directive
name="sles10-cdboot"
Delete the UUID line
Locate the disk definition line. It may look like this:
disk=['file:/root/SLES.iso,hdc:cdrom,r','file:/var/lib/xen/images/sles10-1/disk0,hda,w',]
It this example, the CD-ROM is "hdc" and the hard disk is "hda". The drive numeration for fully virtual booting follows the traditional DOS drive enumeration; that is, hard disk start at "C" and continue up, followed by CD-ROM devices. The default boot is to "C", or the first hard drive. In order to boot from the CD, locate the boot="..." directive. It should look like this:
boot="c"
Change it to DOS enumeration identifier. In our example, their is one hard disk and one CD-ROM, so the DOS enumeration will be "d"
boot="d"
Save and close the file
Since we only want to temporarily boot to the CD-ROM, we are not going to reload the configuration file, but rather discard the configuration after we boot. This is done with the "xm create" command.
xm create SLES10-cdboot
Access the terminal/virtual monitor through "virt-manager", VNC or the typical method
After you are done repairing or booting from CD, shutdown the DomU. Boot the DomU normally.
The SLES10-cdboot file can then be used anytime with the "xm create SLES10-cdboot" command to boot the DomU using the CD.

Example CD-Boot File

The following is an example of a CD-boot DomU configruation file.

ostype="sles10"

name="sles10-cdboot"

memory=512

vcpus=1

on_crash="destroy"

on_poweroff="destroy"

on_reboot="restart"

localtime=0

builder="hvm"

extid=0

device_model="/usr/lib/xen/bin/qemu-dm"

kernel="/usr/lib/xen/boot/hvmloader"

boot="d"

disk=['file:/root/mini.iso,hda:cdrom,r',

'file:/var/lib/xen/images/sles10-1/disk0,hdc,w',]

vif=['mac=00:16:3e:37:bf:64,model=rtl8139,type=ioemu',]

vnc=1

vncunused=1

apic=0

acpi=1

pae=1

Additional Information

Shortcut:

If the CD-Rom is already defined in the configuration file, then you can pass the "boot=d" as a parameter and not need to use the temporary file. For example

xm create SLES10 boot=d
or

xm start SLES10 boot=d

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.