Re: 8.4 Data Not Compatible with 9.0.1 Upgrade?

So I am still in the dark about the entire upgrade or step up process
from 8.4.4-6 to 9.0.1-2. I have my 4 databases all backed up which I
did when my server was 8.4.4-6 using the 'pg_dump' utility. That
worked fine. So after I backed up my databases, I then upgraded the
daemon to 9.0.1-2 and from there I don't understand the process. I
obviously can't connect to the PostgreSQL database after I upgrade
because I get the error:

FATAL: database files are incompatible with server
DETAIL: The data directory was initialized by PostgreSQL version 8.4,
which is not compatible with this version 9.0.1.

I have located the '/usr/bin/pg_upgrade' but I don't understand how I
go about this. I am worried because I have 12 unique database users
with unique / individual grants on specific databases. I don't want to
start from scratch so I would assume this is where the 'pg_upgrade'
script comes into play. How do I proceed from this point on? Obviously
I can't access or connect to PostgreSQL once I upgrade to 9.0.1-2 so I
assume at this time I need to execute the 'pg_upgrade' script to move
forward, right?