问题：
[root@localhost nginx-1.14.2]# /usr/local/nginx/sbin/nginx
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] still could not bind()遇到这种情况，我们首先得知道，他是因为端口被占用了
第一步：如果我们有iptables，我们就跳过这一步，如果没有则安装
yum -y install iptables-services
systemctl mask firewalld.service
systemctl enable iptables.services
systemctl enable ip6tables.services第二步：修改iptables配置文件
vim /etc/sysconfig/iptables添加我们所需要放行的端口
-A INPUT -p tcp -m state --state NEW -m tcp --dport 21 -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT第三步：修改完之后，进行启动
systemctl restart iptables.service
我们在查看一下端口80 lsof -i:80，把进程号给删掉kill -9 进程号第四步:再次启动nginx
/usr/local/nginx/sbin/nginx第五步:进行访问
