Change disk/CD-ROM/DVD during full virtualization installation (XEN)

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Environment

SUSE Linux Enterprise Server 10

Situation

Xen with full virtualization

During installation of some software in full virtualization there is the need to change the CD. An example would be the Small Business Server which consists of 4 CDs. The assumption is that the CDs are on the machine as ISO Files and now there is a need to change CDs.

Resolution

Setting is as follows:

The virtual machine to be installed is named "windows2k".
The ISO images of the CDs are in/isoon dom0.

First it is necessary to find the path to the resource, for this a

xm block-list domX

gives the necessary data. For example:

nil:/etc/xen/vm
# xm block-list
windows2k
Vdev  BE handle state evt-ch ring-ref BE-path
768    0    0     1      -1     -1    /local/domain/0/backend/vbd/37/768
5632   0    0     1      -1     -1    /local/domain/0/backend/vbd/37/5632

The virtual block devices are listed in the order of configuration, so the second entry is for the iso of CD 1.This can be verified by querying the virtual block device with /params appended to it:

xenstore-read /local/domain/0/backend/vbd/37/5632/params

this will give

nil:/etc/xen/vm
# xenstore-read /local/domain/0/backend/vbd/37/5632/params
/iso/en_sbs_2003_cd1.iso

so at the moment the cdrom in the domX is pointing at the iso in /iso/en_sbs_2003_cd1.iso on the dom0.

This can now be changed with

xenstore-write /local/domain/0/backend/vbd/2/5632/params NEWNAME

e.g.

xenstore-write /local/domain/0/backend/vbd/2/5632/params
/iso/en_sbs_2003_cd3.iso

after which /iso/en_sbs_2003_cd3.iso is the new cdrom available to domX.

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