nginx重启出现没有nginx.pid文件的报错
systemctl stop nginx.service
systemctl start nginx.service
systemctl status nginx.service
重新指定启动之时加载的配置文件，然后再重启。
nginx的配置文件目录是：/usr/local/nginx/conf/nginx.conf
1.启动：/usr/local/nginx/sbin/nginx -c /usr/local/nginx/conf/nginx.conf
2.重新加载：/usr/local/nginx/sbin/nginx -s reload
lsof -i:80 查看80端口的程序
netstat -atunp
