secondary name server question

[Techdog]

A newby question here I am sure...

I have a primary and a secondary name server. I have been adding domains to
the primary, and in the NAMED.BOOT file I list each domain as follows:

primary domainname.com domainname.db

I created a domainname.db file with the appropriate DNS information and the
primary works fine. In the domainname.db file I tell it the name of the
secondary name server.

My questions is this: Does the primary server automatically send info to the
secondary for the domain, or do I have to modify the NAMED.BOOT and create
the domainname.db file on the secondary manually? What information do I have
to put in the domainname.db on the secondary server, and what is posted
there by the primary? I am assuming that when changes are made to the
primary and the serial number is incremented, that this information is sent
to the secondary automatically.... is that correct, or do I have to post all
changes manually to the secondary server?

Thanks for any good input!

TD