System has not been booted with systemd as init system (PID 1). Can't operate.
https://www.cnblogs.com/infoo/p/11900607.html
https://www.google.com.hk/search?q=systemctl+start+docker+System+has+not+been+booted+with+systemd+as+init+system+%28PID+1%29.+Can%27t+operate.&newwindow=1&safe=strict&source=hp&ei=NBnTYO3ROcferQGRtb2IDA&iflsig=AINFCbYAAAAAYNMnRC1GFfxZrIXwUZmefrqwD4mMhoIC&oq=systemctl+start+docker+System+has+not+been+booted+with+systemd+as+init+system+%28PID+1%29.+Can%27t+operate.&gs_lcp=Cgdnd3Mtd2l6EANQ0glY0glgsQxoAXAAeACAAQCIAQCSAQCYAQCgAQKgAQGqAQdnd3Mtd2l6sAEA&sclient=gws-wiz&ved=0ahUKEwjtu4Db0a3xAhVHbysKHZFaD8EQ4dUDCAc&uact=5