Send all postgres messages to a specific folder

Hi

In my ubuntu server I have two places where are logged the messages from postgreSql. Some kind of messages are logged in /var/log/postgresql/postgresql-8.1-main.log and others messages are loggued in "/var/log/messages".

I want send all my messages to an specific folder (/var/log/postgresql/) and none of them to "/var/log/messages"

How can I do that?

Thanks in advanced.
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