brew install mongodb 完成后 执行mongod 不能启动

应该是

brew install mongo

然后执行下:

brew info mongo

最下面应该有这么一句:

To reload mongodb after an upgrade:
    launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.mongodb.plist
    launchctl load ~/Library/LaunchAgents/homebrew.mxcl.mongodb.plist
Or, if you don't want/need launchctl, you can just run:
    mongod --config /usr/local/etc/mongod.conf