MySQL multi master replication

This ist HowTo setup MySQL mutli-master replication for fail-over scenarios, a basic step by step guide for setting up a replication system where all nodes act as master and slave at the same time, with a built-in fail-over mechanism.
This can be very useful for sharing SpamAssassin's and dspam's Bayes data and amavisd-new's SQL lookups and storage between mailgateways ;)

mysql replication