# TYPE  DATABASE        USER            ADDRESS                 METHOD

# "local" is for Unix domain socket connections only
local   all             username                                  peer
local   myapp_dev   myapp                               md5
local   myapp_test  myapp                               md5
local   myapp_prod  myapp                               md5
#local   all             all                                     peer
# IPv4 local connections:
host    all             all             127.0.0.1/32            md5
# IPv6 local connections:
host    all             all             ::1/128                 md5
# Allow replication connections from localhost, by a user with the
# replication privilege.
#local   replication     postgres                                peer
#host    replication     postgres        127.0.0.1/32            md5
#host    replication     postgres        ::1/128                 md5

test:

adapter: postgresql
database: myapp_test
pool: 5
timeout: 5000
host: localhost
username: username
password:

sudo -u postgres pg_ctlcluster 9.3 main restart

peer

pg_hba.conf:
# IPv4 local connections:
host    all             all             127.0.0.1/32            trust
# IPv6 local connections:
host    all             all             ::1/128                 trust

default: &default
  adapter: postgresql
  encoding: unicode
  pool: 5
  host: localhost
  username: your_user
  password: your_password

development:
  <<: *default
  database: your_db_development

test:
  <<: *default
  database: your_db_test

production:
  url: <%= ENV['DATABASE_URL'] %>