ssh: connect to host localhost port 22: Connection refused

在安装hadoop环境时，执行start-dfs.sh启动hadoop，一直报这个错

原因：sshd没有开启

解决：

//开启sshd
sudo netsudo launchctl load -w /System/Library/LaunchDaemons/ssh.plist start sshd
//验证开启成功
sudo launchctl list | grep ssh 
//出现

　　0 com.openssh.sshd