centos6.5 安装Mongodb

请问，我在配置好mongo的时候运行 mongo命令。出现这种错误： MongoDB shell version: 2.6.3 connecting to: test 2015-01-16T04:55:36.360-0800 warning: Failed to connect to 127.0.0.1:27017, reason: errno:111 Connection refused 2015-01-16T04:55:36.361-0800 Error: couldn't connect to server 127.0.0.1:27017 (127.0.0.1), connection attempt failed at src/mongo/shell/mongo.js:146 exception: connect failed 我查了资料，把db下面 的mongodb.lock 文件给删掉，但是还是不行。请问问题出现在哪。