Comment 2 for bug 907214

Just installed xcp-xapi on top of a xen installation, and had to run:
update_rc.d xendomains disable
update-rc.d openvswitch-switch disable (I chose 'bridge' in the post install configuration)

There's the /etc/init.d/xend script, and according to:
Workaround XAPI conflicts with XEND (Debian and Ubuntu)
http://wiki.xen.org/wiki/XCP_toolstack_on_a_Debian-based_distribution

"You will need to disable xend from starting in order to get xcp-xapi to start. This is done by modifying the file at /etc/init.d/xend. Many of the setup processes in this script still need to run, but xend itself should not start. This will be resolved in a future release. The command to resolve this is:
sed -i -e 's/xend_start$/#xend_start/' -e 's/xend_stop$/#xend_stop/' /etc/init.d/xend
update-rc.d xendomains disable"

So we still need to run the xend script with the xend_start lines commented out, and it wouldn't conflict with xcp-xapi service.