查看开机启动项
1：systemctl list-unit-files --type=service
2：systemctl list-unit-files --type=service | grep enabled
3：systemctl list-unit-files --type=service | grep disabled
开机停止某个服务：
1：sudo systemctl stop vsftpd.service
2：sudo systemctl disable vsftpd.service
2：sudo systemctl disable vsftpd.service
开机启动某个服务