本文记录MongoDB服务器无法启动解决过程：
1、执行 service mongod start 启动MongoDB服务器，查询（netstat -nat | grep 27017）MongoDB监听端口结果发现没有启动成功。
2、准备查询mongod日志，通过 mongod.conf 配置文件找到日志存放的路径（/var/log/mongodb/mongod.log）；
mongod.conf 配置文件如下：
3、查询mongod 启动失败日志，less /var/log/mongodb/mongod.log 截取错误信息如下
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] MongoDB starting : pid=22507 port=27017 dbpath=/var/lib/mongo 64-bit host=xuexiyuan
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] db version v3.4.10
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] git version: 078f28920cb24de0dd479b5ea6c66c644f6326e9
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] OpenSSL version: OpenSSL 1.0.1e-fips 11 Feb 2013
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] allocator: tcmalloc
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] modules: enterprise
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] build environment:
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] distmod: rhel70
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] distarch: x86_64
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] target_arch: x86_64
2018-03-06T09:47:07.028+0800 I CONTROL [initandlisten] options: { config: "/etc/mongod.conf", net: { port: 27017 }, processManagement: { fork: true, pidFilePath: "/var/run/mongodb/mongod.pid" }, security: { authorization: "enabled" }, storage: { dbPath: "/var/lib/mongo", journal: { enabled: true } }, systemLog: { destination: "file", logAppend: true, path: "/var/log/mongodb/mongod.log" } }
2018-03-06T09:47:07.049+0800 I - [initandlisten] Detected data files in /var/lib/mongo created by the 'wiredTiger' storage engine, so setting the active storage engine to 'wiredTiger'.
2018-03-06T09:47:07.049+0800 I STORAGE [initandlisten]
2018-03-06T09:47:07.049+0800 I STORAGE [initandlisten] ** WARNING: Using the XFS filesystem is strongly recommended with the WiredTiger storage engine
2018-03-06T09:47:07.049+0800 I STORAGE [initandlisten] ** See http://dochub.mongodb.org/core/prodnotes-filesystem
2018-03-06T09:47:07.049+0800 I STORAGE [initandlisten] wiredtiger_open config: create,cache_size=7431M,session_max=20000,eviction=(threads_min=4,threads_max=4),config_base=false,statistics=(fast),log=(enabled=true,archive=true,path=journal,compressor=snappy),file_manager=(close_idle_time=100000),checkpoint=(wait=60,log_size=2GB),statistics_log=(wait=0),
2018-03-06T09:47:07.057+0800 E STORAGE [initandlisten] WiredTiger error (13) [1520300827:57608][22507:0x7f7e92184e40], file:WiredTiger.wt, connection: /var/lib/mongo/WiredTiger.turtle: handle-open: open: Permission denied
2018-03-06T09:47:07.058+0800 I - [initandlisten] Assertion: 28595:13: Permission denied src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp 276
2018-03-06T09:47:07.058+0800 I STORAGE [initandlisten] exception in initAndListen: 28595 13: Permission denied, terminating
2018-03-06T09:47:07.058+0800 I NETWORK [initandlisten] shutdown: going to close listening sockets...
2018-03-06T09:47:07.058+0800 I NETWORK [initandlisten] removing socket file: /tmp/mongodb-27017.sock
2018-03-06T09:47:07.058+0800 I NETWORK [initandlisten] shutdown: going to flush diaglog...
2018-03-06T09:47:07.058+0800 I CONTROL [initandlisten] now exiting
2018-03-06T09:47:07.058+0800 I CONTROL [initandlisten] shutting down with code:100
4、发现启动mongod 服务时存在文件没有权限，因此尝试修改 WiredTiger.turtle 的所属用户，结果还是启动失败，这次通过错误日志看到是该目录下其他文件没有权限。
sudo chown -R mongod:mongod /var/lib/mongo/WiredTiger.turtle
这里面的用户、及用户组mongod 是看到 /var/lib/mongo 目录下大部分文件所属的用户是mongod ，所以用户mongod 用户来尝试。
5、干脆将 /var/lib/mongo 下所有文件所属用户、用户组都改成 mongod，重试后正常启动。
sudo chown -R mongod:mongod /var/lib/mongo
