无法启动MongoDB，mongod始终处于停止/等待状态

我尝试MongoDB在Ubuntu 14.04上运行3.2.4：

sudo service mongod start

并得到结果：

mongod start/running, process 67725

但是，当我检查状态时，我得到：

mongod stop/waiting

我尝试重新安装MongoDB或将Mongo文件夹（lib＆log）的权限定义为root或mongodb。我也试图修复，mongod.conf但没有任何帮助。

日志内容：

2016-04-09T23:56:28.349+0300 I CONTROL  [main] ***** SERVER RESTARTED *****
2016-04-09T23:56:28.359+0300 I CONTROL  [initandlisten] MongoDB starting : pid=69120 port=27017 dbpath=/var/lib/mongodb 64-bit host=is-infomedia
2016-04-09T23:56:28.360+0300 I CONTROL  [initandlisten] db version v3.2.4
2016-04-09T23:56:28.360+0300 I CONTROL  [initandlisten] git version: e2ee9ffcf9f5a94fad76802e28cc978718bb7a30
2016-04-09T23:56:28.360+0300 I CONTROL  [initandlisten] OpenSSL version: OpenSSL 1.0.1f 6 Jan 2014
2016-04-09T23:56:28.360+0300 I CONTROL  [initandlisten] allocator: tcmalloc
2016-04-09T23:56:28.360+0300 I CONTROL  [initandlisten] modules: none
2016-04-09T23:56:28.360+0300 I CONTROL  [initandlisten] build environment:
2016-04-09T23:56:28.360+0300 I CONTROL  [initandlisten]     distmod: ubuntu1404
2016-04-09T23:56:28.360+0300 I CONTROL  [initandlisten]     distarch: x86_64
2016-04-09T23:56:28.360+0300 I CONTROL  [initandlisten]     target_arch: x86_64
2016-04-09T23:56:28.360+0300 I CONTROL  [initandlisten] options: { config: "/etc/mongod.conf", net: { bindIp: "127.0.0.1", port: 27017 }, storage: { dbPath: "/var/lib/mongodb", journal: { enabled: true } }, systemLog: { destination: "file", logAppend: true, path: "/var/log/mongodb/mongod.log" } }
2016-04-09T23:56:28.393+0300 E NETWORK  [initandlisten] Failed to unlink socket file /tmp/mongodb-27017.sock errno:1 Operation not permitted
2016-04-09T23:56:28.393+0300 I -        [initandlisten] Fatal Assertion 28578
2016-04-09T23:56:28.393+0300 I -        [initandlisten] 

***aborting after fassert() failure

更新：

编辑后/etc/mongod.conf：

#security:
authorization: enabled
enableEncryption: true
javascriptEnabled: false

并保存文件，然后尝试重新启动mongod，我收到相同的错误，但是MongoDB没有写入任何日志文件。我检查了的权限，该权限/etc/mongod.conf已分配给mongodb组。mongod编辑其配置文件后如何重新启动？

我的问题：

1. 如何MongoDB在Ubuntu中作为服务运行？
2. 我想念或做错了什么？