启动Nginx报错整理：

1. 报错：ExecStart=/usr/sbin/nginx -c /etc/nginx/nginx.conf (code=exited, status=1/FAILURE)

[root@localhost /etc/nginx/conf.d]# systemctl status nginx
● nginx.service - nginx - high performance web server
   Loaded: loaded (/usr/lib/systemd/system/nginx.service; disabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Sat 2018-11-24 09:50:53 EST; 2h 2min ago
     Docs: http://nginx.org/en/docs/
  Process: 1657 ExecStart=/usr/sbin/nginx -c /etc/nginx/nginx.conf (code=exited, status=1/FAILURE)

Nov 24 09:50:51 mysql-master nginx[1657]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Nov 24 09:50:51 mysql-master nginx[1657]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Nov 24 09:50:52 mysql-master nginx[1657]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Nov 24 09:50:52 mysql-master nginx[1657]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Nov 24 09:50:53 mysql-master nginx[1657]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Nov 24 09:50:53 mysql-master systemd[1]: nginx.service: control process exited, code=exited status=1
Nov 24 09:50:53 mysql-master nginx[1657]: nginx: [emerg] still could not bind()
Nov 24 09:50:53 mysql-master systemd[1]: Failed to start nginx - high performance web server.
Nov 24 09:50:53 mysql-master systemd[1]: Unit nginx.service entered failed state.
Nov 24 09:50:53 mysql-master systemd[1]: nginx.service failed.

• 将Nginxkill掉，重新拉起即可

[root@localhost /etc/nginx/conf.d]# ps -ef |grep nginx
root       2288      1  0 12:06 ?        00:00:00 nginx: master process nginx
nginx      2289   2288  0 12:06 ?        00:00:00 nginx: worker process
root       2291   1283  0 12:06 pts/0    00:00:00 grep --color=auto nginx
[root@localhost /etc/nginx/conf.d]# kill -9 2288      

#重新启动Nginx，加载nginx主配置文件
[root@localhost /etc/nginx/conf.d]# nginx -t -c /etc/nginx/nginx.conf		

2. 修改了nginx的配置文件，绑定了监听8081端口，重启nginx的报错：报错“nginx: [emerg] bind() to 0.0.0.0:8081 failed (13: Permission denied)”：

解决方法：关闭了selinux再启动nginx就好了
[root@localhost /etc/nginx/conf.d]# setenforce 0
setenforce: SELinux is disabled
[root@localhost /etc/nginx/conf.d]# 
# 或者：
[root@localhost /etc/nginx/conf.d]# sed -i 's#^SELINUX=.*$#SELINUX=disabled#g' /etc/selinux/config
[root@mysql-master /etc/nginx/conf.d]# getenforce 
Disabled
[root@localhost /etc/nginx/conf.d]# 

3. pid文件丢失，报错：nginx: [error] open() “/var/run/nginx.pid” failed (2: No such file or directory)

[root@localhost /etc/nginx/conf.d]#  nginx -s reload
nginx: [error] open() "/var/run/nginx.pid" failed (2: No such file or directory)
[root@mysql-master /etc/nginx/conf.d]# 

• 将Nginx kill掉，重新拉起即可

[root@localhost /etc/nginx/conf.d]# ps -ef |grep nginx
root       2288      1  0 12:06 ?        00:00:00 nginx: master process nginx
nginx      2289   2288  0 12:06 ?        00:00:00 nginx: worker process
root       2291   1283  0 12:06 pts/0    00:00:00 grep --color=auto nginx
[root@localhost /etc/nginx/conf.d]# kill -9 2288      

#重新启动Nginx
[root@localhost /etc/nginx/conf.d]# nginx 				

暂时就碰到过这三种启动报错，以后遇到会在补充