解决linux下启动mongodb出现错误的方法：
根据错误信息进入日志文件根据日志文件具体内容中提供的地址获取到修改方式
删除日志文件，以repair方式启动数据库
然后再启动一次数据库，查看进程，如果数据库进程存在，则修复成功
启动错误：
[root@oracleLinux ~]# service mongod start Starting mongod: Fri Jan 24 09:59:59.385 Fri Jan 24 09:59:59.386 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability. Fri Jan 24 09:59:59.387 about to fork child process, waiting until server is ready for connections. forked process: 2120 all output going to: /var/log/mongo/mongod.log ERROR: child process failed, exited with error number 100
日志文件：
ERROR: child process failed, exited with error number 100
日志文件相关内容：
************** Unclean shutdown detected. Please visit http://dochub.mongodb.org/core/repair for recovery instructions. ************* Thu Jan 23 12:34:11.293 [initandlisten] exception in initAndListen: 12596 old lock file, terminating Thu Jan 23 12:34:11.293 dbexit: Thu Jan 23 12:34:11.293 [initandlisten] shutdown: going to close listening sockets... Thu Jan 23 12:34:11.293 [initandlisten] shutdown: going to flush diaglog... Thu Jan 23 12:34:11.293 [initandlisten] shutdown: going to close sockets... Thu Jan 23 12:34:11.293 [initandlisten] shutdown: waiting for fs preallocator... Thu Jan 23 12:34:11.293 [initandlisten] shutdown: closing all files... Thu Jan 23 12:34:11.293 [initandlisten] closeAllFiles() finished Thu Jan 23 12:34:11.293 dbexit: really exiting now
此处是非法关闭mongodb，根据日子文件具体内容中提供的地址（第3行处）获取到修复方式。
a、首先删除/var/lib/mongo/目录下的mongod.lock文件，具体命令如下：
[root@oracleLinux ~]# rm /var/lib/mongo/mongod.lock
b、已repair方式启动mongodb，具体命令如下：
[root@oracleLinux mongo]# mongod -f /etc/mongod.conf --repair Fri Jan 24 10:38:39.112 Fri Jan 24 10:38:39.113 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability. Fri Jan 24 10:38:39.114 about to fork child process, waiting until server is ready for connections. forked process: 2237 all output going to: /var/log/mongo/mongod.log child process started successfully, parent exiting
在启动一次mongodb，具体命令如下：
[root@oracleLinux mongo]# mongod -f /etc/mongod.conf Fri Jan 24 10:41:13.664 Fri Jan 24 10:41:13.665 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability. Fri Jan 24 10:41:13.666 about to fork child process, waiting until server is ready for connections. forked process: 2253 all output going to: /var/log/mongo/mongod.log child process started successfully, parent exiting
查看进程，如果存在mongodb进程，即代表修复成功，具体命令如下：
[root@oracleLinux mongo]# ps -ef | grep mongo root 2253 1 2 10:41 ? 00:00:02 mongod -f /etc/mongod.conf root 2268 2079 0 10:43 pts/0 00:00:00 grep mongo
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