Linux中MongoDB无法正常启动的问题解决办法！
1、报错，导致mongodb无法正常启动。具体命令如下（注意红色字体，提示日志路径，可查看该日志文件）：
[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
[失败]通过输出信息可知，日子文件为/var/log/mongo/mongod.log
错误信息是：
ERROR: child process failed, exited with error number 100[root@oracleLinux ~]# cat /var/log/mongo/mongod.log **************
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.lockb、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 exitingc、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 exitingd、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 mongo3、开始使用mongodb，具体命令如下：
[root@oracleLinux mongo]# mongo
MongoDB shell version: 2.4.9
connecting to: test
Server has startup warnings:
Fri Jan 24 10:41:13.708 [initandlisten]
Fri Jan 24 10:41:13.708 [initandlisten] ** NOTE: This is a 32 bit MongoDB binary.
Fri Jan 24 10:41:13.708 [initandlisten] ** 32 bit builds are limited to less than 2GB of data (or less with --journal).
Fri Jan 24 10:41:13.708 [initandlisten] ** Note that journaling defaults to off for 32 bit and is currently off.
Fri Jan 24 10:41:13.708 [initandlisten] ** See http://dochub.mongodb.org/core/32bit
Fri Jan 24 10:41:13.708 [initandlisten]
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