I am using Rails 3, and Ubuntu. I wish to alter the default Rails SQLite3 right into a mysql database. I went these instructions:

sudo apt-get install mysql-server mysql-client libmysqlclient15-dev
sudo apt-get install libmysql-ruby1.8

They were effective. I Quickly did this within the gemfile

#gem 'sqlite3'
gem 'mysql'

This labored, now, what else must i do in order to complete the MySQL setup. I understand for just one the database.yml must change, but exactly how must it search for Ubuntu and just how will i complete the parameters?

Your config/database.yml must seem like :

base: &base
  adapter: mysql
  username: YourUserName
  password: YourPassword
  host: localhost
  encoding: utf8
  pool: 5
  timeout: 5000
development:
  database: YourApp_dev
  <<: *base
test:
  database: YourApp_test
  <<: *base
production:
  database: YourApp_prod
  <<: *base

edit the database.yml file as appropriate.

e.g.

development:
  adapter: mysql
  database: YourAppsName_development
  username: ******
  password: ******
  pool: 5
  timeout: 5000

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  adapter: mysql
  database: YourAppsName_test
  username: ******
  password: ******
  pool: 5
  timeout: 5000

production:
  database: YourAppsName_production
  adapter: mysql
  pool: 5
  timeout: 5000

This ought to be exactly the same no matter OS. I personally use both Mac and Linux(Ubuntu) machines.

Clearly you will be running your rake db:create (and migrate, seed, etc.)

May be the database on a single host?

You have to log into mysql, set a person, produce a database. When the database is on the database server, outdoors from the application server, then you will have to make accessible in the internet.

http://www.slac.stanford.edu/BFROOT/www/Computing/Online/Databases/CfgDB/CfgDB-MySQL-Setup.html

After you are done establishing the database (not only setting up it), then you are database.yml files have to be modified per the above mentioned.