I've just started to study Rails.
When I try "rake db:migrate", the following error occured.

> 
> rake aborted!
>  FATAL: Peer authentication failed for user "kt1"
> 
> 
> 

it seems there's something wrong with database.yml but I have no idea how to solve.
Please give me an advice.

---

Thank you very much for your comment and edit. I'm using postgresql (0.13.2). My environment is as follows.
Ubuntu 11.10
Ruby 1.8.7
Rails 3.2.3
gem 1.8.21

database.yml as below.

---

```
# PostgreSQL. Versions 8.2 and up are supported.
#
# Install the pg driver:
#   gem install pg
# On Mac OS X with macports:
#   gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config
# On Windows:
#   gem install pg
#       Choose the win32 build.
#       Install PostgreSQL and put its /bin directory on your path.
#
# Configure Using Gemfile
# gem 'pg'
#
development:
  adapter: postgresql
  encoding: unicode
  database: kt1_development
  pool: 5
  username: kt1
  password:

  # Connect on a TCP socket. Omitted by default since the client uses a
  # domain socket that doesn't need configuration. Windows does not have
  # domain sockets, so uncomment these lines.
  #host: localhost
  #port: 5432

  # Schema search path. The server defaults to $user,public
  #schema_search_path: myapp,sharedapp,public

  # Minimum log levels, in increasing order:
  #   debug5, debug4, debug3, debug2, debug1,
  #   log, notice, warning, error, fatal, and panic
  # The server defaults to notice.
  #min_messages: warning

# 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: postgresql
  encoding: unicode
  database: kt1_test
  pool: 5
  username: kt1
  password:

production:
  adapter: postgresql
  encoding: unicode
  database: kt1_production
  pool: 5
  username: kt1
  password:

```

---

I also tried with username in blank. Then the error comes to

```
rake aborted!
FATAL:  role "kenji" does not exist

```

(kenji is my username on Ubuntu.)