1.系统环境
vps主机：https://www.vultr.com
os：Ubuntu 18*64
2.重启nginx失败，具体排查过程记录如下：
step 1：首先检查80端口是否监听
root@vultr:~# netstat -ntlp发现80和443端口没有被nginx监听
output:
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:6000 0.0.0.0:* LISTEN 542/dotnet
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN 497/systemd-resolve
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 674/sshd
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1332/cupsd
tcp 0 0 127.0.0.1:6010 0.0.0.0:* LISTEN 19401/sshd: root@pt
tcp 0 0 0.0.0.0:443 0.0.0.0:* LISTEN 656/select
tcp 0 0 127.0.0.1:5000 0.0.0.0:* LISTEN 32686/dotnet
tcp6 0 0 :::40491 :::* LISTEN 608/array
tcp6 0 0 ::1:6000 :::* LISTEN 542/dotnet
tcp6 0 0 :::22 :::* LISTEN 674/sshd
tcp6 0 0 ::1:631 :::* LISTEN 1332/cupsd
tcp6 0 0 ::1:6010 :::* LISTEN 19401/sshd: root@pt
tcp6 0 0 ::1:5000 :::* LISTEN 32686/dotnet
step 2：执行重启nginx命令，看看是个什么情况
root@vultr:~# service nginx restart启动失败提示信息：
Job for nginx.service failed because the control process exited with error code.
See "systemctl status nginx.service" and "journalctl -xe" for details.
root@vultr:~# systemctl 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 Fri 2020-04-24 12:36:17 UTC; 1min 18s ago
Docs: man:nginx(8)
Process: 19612 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code=exited, status=1/FAILURE)
Process: 19602 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process on; (code=exited, status=0
Apr 24 12:36:14 vultr.guest systemd[1]: Starting A high performance web server and a reverse proxy server..
Apr 24 12:36:14 vultr.guest nginx[19612]: nginx: [emerg] bind() to 0.0.0.0:443 failed (98: Address already
Apr 24 12:36:15 vultr.guest nginx[19612]: nginx: [emerg] bind() to 0.0.0.0:443 failed (98: Address already
Apr 24 12:36:15 vultr.guest nginx[19612]: nginx: [emerg] bind() to 0.0.0.0:443 failed (98: Address already
Apr 24 12:36:16 vultr.guest nginx[19612]: nginx: [emerg] bind() to 0.0.0.0:443 failed (98: Address already
Apr 24 12:36:16 vultr.guest nginx[19612]: nginx: [emerg] bind() to 0.0.0.0:443 failed (98: Address already
Apr 24 12:36:17 vultr.guest nginx[19612]: nginx: [emerg] still could not bind()
Apr 24 12:36:17 vultr.guest systemd[1]: nginx.service: Control process exited, code=exited status=1
Apr 24 12:36:17 vultr.guest systemd[1]: nginx.service: Failed with result 'exit-code'.
Apr 24 12:36:17 vultr.guest systemd[1]: Failed to start A high performance web server and a reverse proxy s
step 3：检查nginx配置是否正确
因为曾经修改过nginx配置参数，首先检查nginx配置是否正确
执行检查nginx配置命令
root@vultr:~# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
配置没有问题
step 4：查看ngix错误日志
vi /var/log/nginx/error.logoutput:
2020/04/24 12:40:00 [emerg] 19889#19889: bind() to 0.0.0.0:443 failed (98: Address already in use)
2020/04/24 12:40:00 [emerg] 19889#19889: bind() to 0.0.0.0:443 failed (98: Address already in use)
2020/04/24 12:40:00 [emerg] 19889#19889: still could not bind()
提示端口被占用了，怪不得nginx启动失败。
step 4：查看是哪个程序占用了该端口
ps -ef |grep nginx
netstat -tln | grep 443
lsof -i :443