centos7操作SSH/SSHD服务，查看/启动/重启/自启
查看状态：
systemctl status sshd.service
启动服务：
systemctl start sshd.service
重启服务：
systemctl restart sshd.service
开机自启：
systemctl enable sshd.service
systemctl status sshd.service
systemctl start sshd.service
systemctl restart sshd.service
systemctl enable sshd.service
