longfellow@ubuntu:~/node$ systemctl -l status nginx.service
● nginx.service - A high performance web server and a reverse proxy server
Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since 二 2015-12-29 03:05:50 CST; 11min ago
Process: 4662 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=1/FAILURE)
12月 29 03:05:49 ubuntu systemd[1]: Starting A high performance web server and a reverse proxy server...
12月 29 03:05:50 ubuntu nginx[4662]: nginx: [emerg] unknown directive "root.html" in /etc/nginx/sites-enabled/default:53
12月 29 03:05:50 ubuntu nginx[4662]: nginx: configuration file /etc/nginx/nginx.conf test failed
12月 29 03:05:50 ubuntu systemd[1]: nginx.service: Control process exited, code=exited status=1
12月 29 03:05:50 ubuntu systemd[1]: Failed to start A high performance web server and a reverse proxy server.
12月 29 03:05:50 ubuntu systemd[1]: nginx.service: Unit entered failed state.
12月 29 03:05:50 ubuntu systemd[1]: nginx.service: Failed with result 'exit-code'.nginx: [emerg] unknown directive "root.html" in /etc/nginx/sites-enabled/default:53
你的配置文件第 53 行, 写的路径不正确.