使某服务自动启动	chkconfig –level 3 httpd on	systemctl enable httpd.service
使某服务不自动启动	chkconfig –level 3 httpd off	systemctl disable httpd.service
检查服务状态	service httpd status	systemctl status   httpd.service （服务详细信息） systemctl is-active httpd.service （仅显示是否 Active)
显示所有已启动的服务	chkconfig –list	systemctl list-units –type=service
启动某服务	service httpd start	systemctl start httpd.service
停止某服务	service httpd stop	systemctl stop httpd.service
重启某服务	service httpd restart	systemctl restart httpd.service