linux中安装mongoDB之后，启动不了，出现下边的错误，网上搜原因，很多说需要删除.lock文件，需要bin/mongod --repair修复，但是都不成功，最后发现是配置文件中路径问题。

[root@wqd mongodb]# bin/mongod -f single/mongod.conf 
about to fork child process, waiting until server is ready for connections.
forked process: 8962
ERROR: child process failed, exited with error number 1
To see additional information in this output, start without the "--fork" option.

解决：
先用bin/mongod --repair去修复，看一些信息

[root@wqd mongodb]# bin/mongod --repair
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten] MongoDB starting : pid=8972ort=27017 dbpath=/data/db 64-bit host=wqd
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten] db version v4.0.10
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten] git version: c389e7f69f637f1ac3cc9fae843b635f20b766
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten] allocator: tcmalloc
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten] modules: none
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten] build environment:
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten]     distarch: x86_64
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten]     target_arch: x86_64
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten] options: { repair: true }
2021-06-23T13:48:28.746+0800 I STORAGE  [initandlisten] exception in initAndListen:onExistentPath: Data directory /data/db not found., terminating
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten] now exiting
2021-06-23T13:48:28.746+0800 I CONTROL  [initandlisten] shutting down with code:1

最重要的是倒数第三句exception in initAndListen: NonExistentPath: Data directory /data/db not found., terminating
配置文件中data/db路径有问题
修改路径从根目录开始"/usr/local/mongodb/single/data/db"
全部配置如下：

再次启动成功