几天前，我能够成功安装PostgreSQL并从SQLite创建/迁移我的数据库（准备部署Rails 4应用程序）...或我想。
我重新启动了我的服务器，但是当我尝试访问我的应用时，我会收到此错误：
PG::ConnectionBad
could not connect to server: Connection refused
Is the server running locally and accepting connections on Unix domain socket
"/var/run/postgresql/.s.PGSQL.5432"?
我已经看到了几个类似的回答问题，但是它们都涉及Mac。由于我使用的是云9 IDE，所以我认为可能存在差异（例如，localhost的提及可能无关紧要，因为这不是我当前在C9.IO上访问该应用的方式。）
根据其他问题的答案，我在终端中尝试了一下：
sudo ps auxw | grep post
给了我：
ubuntu 2527 0.0 0.0 10552 888 pts/5 S+ 15:21 0:00 grep --color=auto post
然后我尝试了：
sudo find / -name .s.PGSQL.5432 -ls
我得到了：
5286 0 lrwxrwxrwx 1 root root 26 May 11 15:13 /var/pgsql_socket/.s.PGSQL.5432 -> /private/tmp/.s.PGSQL.5432
5183 0 srwxrwxrwx 1 postgres postgres 0 May 10 22:18 /run/postgresql/.s.PGSQL.5432
yamilethmedina@wheels_registration:~/workspace (master|MERGING) $ psql
psql: could not connect to server: Connection refused
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
这是我的服务器的完整跟踪：
Started GET "/" for 12.43.117.2 at 2015-05-11 16:35:48 +0000
PG::ConnectionBad (could not connect to server: Connection refused
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
):
activerecord (4.1.6) lib/active_record/connection_adapters/postgresql_adapter.rb:888:in `initialize'
activerecord (4.1.6) lib/active_record/connection_adapters/postgresql_adapter.rb:888:in `new'
activerecord (4.1.6) lib/active_record/connection_adapters/postgresql_adapter.rb:888:in `connect'
activerecord (4.1.6) lib/active_record/connection_adapters/postgresql_adapter.rb:568:in `initialize'
activerecord (4.1.6) lib/active_record/connection_adapters/postgresql_adapter.rb:41:in `new'
activerecord (4.1.6) lib/active_record/connection_adapters/postgresql_adapter.rb:41:in `postgresql_connection'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:435:in `new_connection'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:445:in `checkout_new_connection'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:416:in `acquire_connection'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:351:in `block in checkout'
/usr/local/rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:350:in `checkout'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:265:in `block in connection'
/usr/local/rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:264:in `connection'
activerecord (4.1.6) lib/active_record/connection_adapters/abstract/connection_pool.rb:541:in `retrieve_connection'
activerecord (4.1.6) lib/active_record/connection_handling.rb:113:in `retrieve_connection'
activerecord (4.1.6) lib/active_record/connection_handling.rb:87:in `connection'
activerecord (4.1.6) lib/active_record/migration.rb:388:in `check_pending!'
activerecord (4.1.6) lib/active_record/migration.rb:377:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.1.6) lib/active_support/callbacks.rb:82:in `run_callbacks'
actionpack (4.1.6) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/reloader.rb:73:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.1.6) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.1.6) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.1.6) lib/active_support/tagged_logging.rb:68:in `block in tagged'
activesupport (4.1.6) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport (4.1.6) lib/active_support/tagged_logging.rb:68:in `tagged'
railties (4.1.6) lib/rails/rack/logger.rb:20:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.1.6) lib/active_support/cache/strategy/local_cache_middleware.rb:26:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.1.6) lib/action_dispatch/middleware/static.rb:64:in `call'
rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
railties (4.1.6) lib/rails/engine.rb:514:in `call'
railties (4.1.6) lib/rails/application.rb:144:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
/usr/local/rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
/usr/local/rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
/usr/local/rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'
Rendered /usr/local/rvm/gems/ruby-2.1.5@rails4/gems/actionpack-4.1.6/lib/action_dispatch/middleware/templates/rescues/_source.erb (1.1ms)
Rendered /usr/local/rvm/gems/ruby-2.1.5@rails4/gems/actionpack-4.1.6/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (3.8ms)
Rendered /usr/local/rvm/gems/ruby-2.1.5@rails4/gems/actionpack-4.1.6/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (2.9ms)
Rendered /usr/local/rvm/gems/ruby-2.1.5@rails4/gems/actionpack-4.1.6/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (45.7ms)
我的整个github存储库以防万一：https://github.com/yamilethmedina/wheels_registration.git
看起来不像PostgreSQL正在运行。也许它没有设置为自动启动。原因之一可能是，如果PostgreSQL在最后一次运行中没有干净地关闭，并且留下一个PID文件。
尝试
sudo service postgresql start
看看它是否返回，只需确保您关闭VM（以便停止脚本可以运行），而不是将其关闭。