不多说，直接上干货！
前期博客
Ubuntu14.04下Mongodb安装部署步骤（图文详解）
Ubuntu16.04下Mongodb安装部署步骤（图文详解）
root@zhouls-virtual-machine:/usr/local/mongodb/bin# ls
bsondump mongodump mongoimport mongoreplay mongostat
mongo mongoexport mongooplog mongorestore mongotop
mongod mongofiles mongoperf mongos
root@zhouls-virtual-machine:/usr/local/mongodb/bin# ./mongod --dbpath=/usr/local/mongodb/data/ --fork --logpath=/usr/local/mongodb/log
about to fork child process, waiting until server is ready for connections.
forked process: 5784
ERROR: child process failed, exited with error number 1
root@zhouls-virtual-machine:/usr/local/mongodb/bin#
失败的原因
是因为通过service MongoDB restart时启动失败，或者如果是直接kill 掉来关闭都会出现这种情况
是因为没有正常关闭导致的。
是因为你的配置目录，是否应该要是log配置文件，而很多人都写成了log目录。
解决办法
zhouls@zhouls-virtual-machine:~$ sudo ufw disable
[sudo] password for zhouls:
Firewall stopped and disabled on system startup
zhouls@zhouls-virtual-machine:~$
root@zhouls-virtual-machine:/usr/local/mongodb# ls
bin data GNU-AGPL-3.0 log MPL- README THIRD-PARTY-NOTICES
root@zhouls-virtual-machine:/usr/local/mongodb# rm -rf log/
root@zhouls-virtual-machine:/usr/local/mongodb# ls
bin data GNU-AGPL-3.0 MPL- README THIRD-PARTY-NOTICES
root@zhouls-virtual-machine:/usr/local/mongodb# touch log
root@zhouls-virtual-machine:/usr/local/mongodb# cd bin
root@zhouls-virtual-machine:/usr/local/mongodb/bin# pwd
/usr/local/mongodb/bin
root@zhouls-virtual-machine:/usr/local/mongodb/bin# ls
bsondump mongodump mongoimport mongoreplay mongostat
mongo mongoexport mongooplog mongorestore mongotop
mongod mongofiles mongoperf mongos
root@zhouls-virtual-machine:/usr/local/mongodb/bin# ./mongod --dbpath=/usr/local/mongodb/data/ --fork --logpath=/usr/local/mongodb/log
about to fork child process, waiting until server is ready for connections.
forked process:
child process started successfully, parent exiting
root@zhouls-virtual-machine:/usr/local/mongodb/bin#