刚开始一直报500错误，页面不提示，也没想着去查看日志文件。好几天了，一看日志，发现是这个问题。问了一下，是session的问题、
2017/07/25 16:57:49 [error] 2300#0: *1 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught exception 'yiiaseErrorException' with message 'session_write_close(): open(/var/lib/php/session/sess_itrssn0785o64bpt6b9n2utl91, O_RDWR) failed: Permission denied (13)' in /mnt/hgfs/UnknownBlog/vendor/yiisoft/yii2/web/Session.php:187
Stack trace:
#0 [internal function]: yiiaseErrorHandler->handleError(2, 'session_write_c...', '/mnt/hgfs/Unkno...', 187, Array)
#1 /mnt/hgfs/UnknownBlog/vendor/yiisoft/yii2/web/Session.php(187): session_write_close()
#2 [internal function]: yiiwebSession->close()
#3 {main}
thrown in /mnt/hgfs/UnknownBlog/vendor/yiisoft/yii2/web/Session.php on line 187" while reading response header from upstream, client: 192.168.1.102, server: admin.blog.org, request: "GET /login/index HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "admin.blog.org", referrer: "http://admin.blog.org/login/index"
关于这个错误，是session权限问题
在index.php 打印phpinfo（）;查看session的目录
然后给session设置777权限；解决
chmod -R 777 /var/lib/php/session