rc.local
/etc/init.d/nginx start查看运行状态
systemctl status rc-local● rc-local.service - /etc/rc.local Compatibility
Loaded: loaded (/lib/systemd/system/rc-local.service; static; vendor preset: enabled)
Drop-In: /lib/systemd/system/rc-local.service.d
└─debian.conf
Active: failed (Result: exit-code) since 六 2018-07-07 09:40:03 CST; 5min ago
Process: 1112 ExecStart=/etc/rc.local start (code=exited, status=1/FAILURE)
7月 07 09:40:03 Ubuntu systemd[1]: Starting /etc/rc.local Compatibility...
7月 07 09:40:03 Ubuntu rc.local[1112]: Starting nginx... nginx: [emerg] host not found in upstr
7月 07 09:40:03 Ubuntu rc.local[1112]: failed
7月 07 09:40:03 Ubuntu systemd[1]: rc-local.service: Control process exited, code=exited status
7月 07 09:40:03 Ubuntu systemd[1]: Failed to start /etc/rc.local Compatibility.
7月 07 09:40:03 Ubuntu systemd[1]: rc-local.service: Unit entered failed state.
7月 07 09:40:03 Ubuntu systemd[1]: rc-local.service: Failed with result 'exit-code'.
发现是失败的，原因大概是没有exit 0，再次尝试重启
rc.local
/etc/init.d/nginx start
exit 0重启rclocal
systemctl restart rc-local● rc-local.service - /etc/rc.local Compatibility
Loaded: loaded (/lib/systemd/system/rc-local.service; static; vendor preset: enabled)
Drop-In: /lib/systemd/system/rc-local.service.d
└─debian.conf
Active: active (running) since 六 2018-07-07 09:46:42 CST; 1min 49s ago
Process: 3796 ExecStart=/etc/rc.local start (code=exited, status=0/SUCCESS)
Main PID: 3801 (nginx)
CGroup: /system.slice/rc-local.service
├─3801 nginx: master process /usr/local/nginx/sbin/nginx -c /usr/local/nginx/conf/ng
├─3804 nginx: worker process
├─3805 nginx: worker process
├─3806 nginx: worker process
└─3807 nginx: worker process
7月 07 09:46:42 Ubuntu systemd[1]: Starting /etc/rc.local Compatibility...
7月 07 09:46:42 Ubuntu rc.local[3796]: Starting nginx... done
再次查看状态，发现成功了nginx。通过这两条指令不需要每次都重启电脑进行调试了，而且重启电脑也不知道什么原因会启动失败。
可以通过这样来检测开机启动是否能成功，而不是每次都要重启，重启！
还可以查看其他服务的启动情况！
systemctl status nginx
● nginx.service - LSB: starts the nginx web server
Loaded: loaded (/etc/init.d/nginx; bad; vendor preset: enabled)
Active: failed (Result: exit-code) since 六 2018-07-07 10:13:22 CST; 3min 33s ago
Docs: man:systemd-sysv-generator(8)
Process: 939 ExecStart=/etc/init.d/nginx start (code=exited, status=1/FAILURE)
7月 07 10:13:17 Ubuntu systemd[1]: Starting LSB: starts the nginx web server...
7月 07 10:13:22 Ubuntu nginx[939]: Starting nginx... nginx: [emerg] host not found in upstream
7月 07 10:13:22 Ubuntu nginx[939]: failed
7月 07 10:13:22 Ubuntu systemd[1]: nginx.service: Control process exited, code=exited status=1
7月 07 10:13:22 Ubuntu systemd[1]: Failed to start LSB: starts the nginx web server.
7月 07 10:13:22 Ubuntu systemd[1]: nginx.service: Unit entered failed state.
7月 07 10:13:22 Ubuntu systemd[1]: nginx.service: Failed with result 'exit-code'.