Almost perfect setup - see Centreon Wiki:
http://en.doc.centreon.com/Nagios3_Centreon2_Ubuntu

Notes:
Ubuntu specific adjustments are not needed anymore.

After installation hints:
http://www.evil.cz/clanek/nagios-centreon-how-delete-localhost-host

Problem: I've installed Nagios 3.04, ndo-utils 1.4b7, and centreon 2 rc7. After I exported the settings from centreon to nagios, I see in centreon under monitoring 2 hosts: localhost and centreon-server. Under configuration, hosts, I see only the centreon-server. Also in Nagios I see only centreon-server and not localhost. How can I delete localhost?

Problem: no outgoing mails from Nagios/Centreon server with Exim4 after installation.
Solution: dpkg-reconfigure exim4-config
Explanation: exim4 default installation on Ubuntu 8.10 is "local mail only". You need "Internet computer" instead.

Do NOT forget after installation:
http://www.nagios.org/faqs/viewfaq.php?faq_id=228

Short how-to w/o any explanation. You HAVE TO know what you are doing at this level of using linux server! Do NOT experiment on a production server!