title: django.db.utils.OperationalError: could not connect to server: No such file or directory
body: <p>my setting of database in settings.py is below</p>
  
  <pre><code>DATABASES = {
      'default': {
          'ENGINE': 'django.db.backends.postgresql_psycopg2',
          'NAME': 'dbname',
          'USER': 'postgres',
          'PASSWORD': 'postgres',
          'HOST': '',
          'PORT':'8081',
      }
  }
  </code></pre>
  
  <p>but when running python manage.py migrate 
  i am getting error django.db.utils.OperationalError: could not connect to server: No such file or directory</p>
  
  <pre><code>Traceback (most recent call last):
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/backends/base/base.py", line 130, in ensure_connection
      self.connect()
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/backends/base/base.py", line 119, in connect
      self.connection = self.get_new_connection(conn_params)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/backends/postgresql_psycopg2/base.py", line 176, in get_new_connection
      connection = Database.connect(**conn_params)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/psycopg2/__init__.py", line 164, in connect
      conn = _connect(dsn, connection_factory=connection_factory, async=async)
  psycopg2.OperationalError: could not connect to server: No such file or directory
      Is the server running locally and accepting
      connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.8081"?
  
  
  The above exception was the direct cause of the following exception:
  
  Traceback (most recent call last):
    File "manage.py", line 10, in &lt;module&gt;
      execute_from_command_line(sys.argv)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
      utility.execute()
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/core/management/__init__.py", line 330, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/core/management/base.py", line 393, in run_from_argv
      self.execute(*args, **cmd_options)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/core/management/base.py", line 444, in execute
      output = self.handle(*args, **options)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/core/management/commands/migrate.py", line 93, in handle
      executor = MigrationExecutor(connection, self.migration_progress_callback)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/migrations/executor.py", line 19, in __init__
      self.loader = MigrationLoader(self.connection)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/migrations/loader.py", line 47, in __init__
      self.build_graph()
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/migrations/loader.py", line 182, in build_graph
      self.applied_migrations = recorder.applied_migrations()
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/migrations/recorder.py", line 59, in applied_migrations
      self.ensure_schema()
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/migrations/recorder.py", line 49, in ensure_schema
      if self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor()):
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/backends/base/base.py", line 162, in cursor
      cursor = self.make_debug_cursor(self._cursor())
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/backends/base/base.py", line 135, in _cursor
      self.ensure_connection()
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/backends/base/base.py", line 130, in ensure_connection
      self.connect()
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/utils.py", line 97, in __exit__
      six.reraise(dj_exc_type, dj_exc_value, traceback)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/utils/six.py", line 658, in reraise
      raise value.with_traceback(tb)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/backends/base/base.py", line 130, in ensure_connection
      self.connect()
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/backends/base/base.py", line 119, in connect
      self.connection = self.get_new_connection(conn_params)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/django/db/backends/postgresql_psycopg2/base.py", line 176, in get_new_connection
      connection = Database.connect(**conn_params)
    File "/home/vivekpradhan/joker/basket/local/lib/python3.4/site-packages/psycopg2/__init__.py", line 164, in connect
      conn = _connect(dsn, connection_factory=connection_factory, async=async)
  django.db.utils.OperationalError: could not connect to server: No such file or directory
      Is the server running locally and accepting
      connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.8081"?
  </code></pre>
  
  <p>any help will be helpful thanks in advance
  I am working on a ubantu os.</p>