Развертывание Capistrano — Net::SSH::AuthenticationFailed — AWS EC2

Почему я получаю authenicationFailed при попытке запустить установку развертывания? Я использую ssh в качестве пароля. Нужно ли что-то менять в файле database.yml или deploy.rb. Они перечислены ниже.

$ cap deploy:setup
  * executing `deploy:setup'
  * executing "sudo -p 'sudo password: ' mkdir -p /var/www/apps/sample_app /var/www/apps/sample_app
 /releases /var/www/apps/sample_app/shared /var/www/apps/sample_app/shared/system /var/www     
/apps/sample_app/shared/log /var/www/apps/sample_app/shared/pids"
    servers: ["ec2-20-21-42-51.compute-1.amazonaws.com"]
Password: 
connection failed for: ec2-20-21-42-51.compute-1.amazonaws.com 
(Net::SSH::AuthenticationFailed: ubuntu)

deploy.rb

# The name of your app
set :application, "sample_app"

# The directory on the EC2 node that will be deployed to
set :deploy_to, "/var/www/apps/#{application}"

set :keep_releases, 3

# deploy with git
set :scm, :git
set :repository,  "git@github.com:username/sample_app.git"
set :git_shallow_clone, 1
set :branch, "master"
set :use_sudo, true

set :user, "ubuntu"
ssh_options[:forward_agent] = true
default_run_options[:pty] = true

# The address of the remote host on EC2 (the Public DNS address)
set :location, "ec2-20-21-42-51.compute-1.amazonaws.com"

# setup some Capistrano roles
role :app, location
role :web, location
role :db,  location, :primary => true

after 'deploy:update_code', 'deploy:symlink_db'


namespace :deploy do

desc "Restart Application"
task :restart, :roles => :app do
run "touch #{deploy_to}/#{shared_dir}/tmp/restart.txt"
end

desc "Symlinks the database.yml"
task :symlink_db, :roles => :app do
run "ln -nfs #{deploy_to}/shared/config/database.yml #{release_path}/config/database.yml"
end

end

database.yml

development:
  adapter: mysql2
  database: db/development.mysql2
  pool: 5
  timeout: 5000
  database: sample_app
  username: root
  socket: /tmp/mysql.sock

test:
  adapter: mysql2
  database: db/test.mysql2
  pool: 5
  timeout: 5000
  database: sample_app
  username: root
  socket: /tmp/mysql.sock

production:
  adapter: mysql2
  database: db/production.mysql2
  pool: 5
  timeout: 5000
  database: sample_app
  username: ubuntu
  socket: /var/run/mysqld/mysqld.sock