Mac环境下MongoDB无法启动

解决方法1

原因：mongodb没有启动

用brew service来启动
brew services start mongodb

解决方法2

原因：没有db文件夹

Before you start MongoDB for the first time, create the directory to which the mongod process will write data. By default, the mongod process uses the /data/db directory. If you create a directory other than this one, you must specify that directory in the dbpath option when starting the mongod process later in this procedure.

1. 创建文件夹
mkdir -p /data/db
2. 给文件夹设置可写
sudo chown -R `id -un` /data/db
3. 运行mongodb
cd /usr/local/mongodb/bin
mongod
mongo
4. 结束运行mongodb
Control+C

解决方法3

原因：因意外造成Mongodb服务非正常关闭且造成Mongod服务无法正常启动

删除data目录下的*.lock文件
sudo rm /data/db/mongod.lock
sudo rm /data/db/WiredTiger.lock
然后再启动Mongod服务
cd /usr/local/mongodb/bin
mongod
mongo

如果还是不行，可以查看一下进程，然后杀掉：
ps -aef | grep mongo 
kill ***
cd /usr/local/mongodb/bin
mongod
mongo

解决方法4

原因：Permission denied

cd /usr/local/mongodb/bin
sudo mongod