我在启动mongod进程时收到以下错误：
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2018-07-11T18:23:29.412+0000 I STORAGE [initandlisten] exception in initAndListen: 12596 old lock file, terminating
2018-07-11T18:23:29.412+0000 I CONTROL [initandlisten] dbexit: rc: 100
2018-07-11T18:23:59.577+0000 I CONTROL ***** SERVER RESTARTED *****
2018-07-11T18:23:59.584+0000 I CONTROL [initandlisten] MongoDB starting : pid=1657 port=27017 dbpath=/var/lib/mongodb 64-bit host=ip-172-31-26-170
2018-07-11T18:23:59.584+0000 I CONTROL [initandlisten] db version v3.0.12
2018-07-11T18:23:59.584+0000 I CONTROL [initandlisten] git version: 33934938e0e95d534cebbaff656cde916b9c3573
2018-07-11T18:23:59.584+0000 I CONTROL [initandlisten] build info: Linux ip-10-229-66-2 3.13.0-24-generic #46-Ubuntu SMP Thu Apr 10 19:11:08 UTC 2014 x86_64 BOOST_LIB_VERSION=1_49
2018-07-11T18:23:59.584+0000 I CONTROL [initandlisten] allocator: tcmalloc
2018-07-11T18:23:59.584+0000 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" } }
2018-07-11T18:23:59.625+0000 W - [initandlisten] Detected unclean shutdown - /var/lib/mongodb/mongod.lock is not empty.
2018-07-11T18:23:59.634+0000 I STORAGE [initandlisten] **************
old lock file: /var/lib/mongodb/mongod.lock. probably means unclean shutdown,
but there are no journal files to recover.
this is likely human error or filesystem corruption.
please make sure that your journal directory is mounted.
found 4 dbs.
see: http://dochub.mongodb.org/core/repair for more information
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2018-07-11T18:23:59.634+0000 I STORAGE [initandlisten] exception in initAndListen: 12596 old lock file, terminating
2018-07-11T18:23:59.634+0000 I CONTROL [initandlisten] dbexit: rc: 100
每次启动mongod服务后，它都会自行停止运行
ubuntu@ip-172-/admin$ sudo service mongod start
mongod start/running, process 8844
ubuntu@ip-172-/admin$ sudo service mongod status
mongod stop/waiting
我该怎么做才能使mongod在ec2中再次运行？