How do I configure Rails for password-less access to remote database

There is also a pure rails solution

add the following to your Gemfile

 gem 'net-ssh-gateway'

then create a class

module RemoteConnectionManager
  SSH_USER = 'YOUR_SSH_USER'

  def self.port_through_tunnel(remote_host, port, local_port: nil, db_host:'localhost')
    return Net::SSH::Gateway.new(remote_host, SSH_USER)
      .open(db_host,port,local_port)
  end
end

last change your database.yml

  adapter: mysql2
    host: 127.0.0.1
    port:  <%= RemoteConnectionManager.port_through_tunnel('your_ssh_host', 3306, db_host: 'your_db_host_eg_some_aws_rds_db' ) %>
    username: your_db_username
    password: your_db_password
    database: your_db_name

if local_port is nil Net/ssh will pick a free one

First, you need to establish an SSH tunnel the MySQL server. On the client machine, run:

ssh -fNg -L 3307:127.0.0.1:3306 [email protected]

That will establish an SSH tunnel to the salt.woofwoof.com server. Any connections to localhost port 3307 will get sent through the tunnel to the remote host on port 3306.

Then just configure your database.yml like you would for a local connection, but specify the forwarded port 3307:

canine:
  adapater: mysql2
  database: canine
  username: bowser
  password: *secret*
  port: 3307

You may also want to add the ssh tunnel setup to /etc/inittab so that the tunnel is establish after boot. See http://chxo.com/be2/20040511_5667.html for one example of how to do that.