MySQL_Master_Db_Magic.rb

desc "get Master"
task :get_master_info, :roles => :new do
  run 'echo "SHOW MASTER STATUS" | mysql -u root --password=root_pass' do |ch, stream, data|
    set :master_info, data.split("\n").pop().split("\t")
  end
  
  set_master

end

desc "Set Master on Slave"
task :set_master, :roles => :old do
  set :sql, "CHANGE MASTER TO MASTER_HOST='some.host', MASTER_USER='user', MASTER_PASSWORD='some_pa55', MASTER_LOG_FILE='#{master_info[0]}', MASTER_LOG_POS=#{master_info[1]};"

  # puts sql  
  put(sql, "/tmp/master.sql")
  run "cat /tmp/master.sql | mysql -u root --password=root_pass"
  
end

Number 1 in a continuing series of things you probably shouldn't do with Capistrano.