nginx.pid打开失败以及失效的解决方案

报错：

> ./nginx -s reload
nginx: [error] open() "/var/run/nginx/nginx.pid" failed (2: NO such file or directory)
> cd /var/run/nginx
-bash: cd: /var/run/nginx: 没有那个文件或目录

先创建 缺失的目录，此时若依旧不能重启

> mkdir /var/run/nginx
> ./nginx -s reload
nginx: [error] invalid PID number "" in "/var/run/nginx/nginx.pid"

重新指定一次配置文件位置 即可解决

> ./nginx -c /usr/local/nginx/conf/nginx.conf
> ./nginx -s reload