PROBLEM
A routine software update on the server running nginx was done. After that the website stopped opening in the browser window and 502 Bad Gateway
error along with the nginx version number was displayed. Looking in the log file showed an entry like,
2014/06/26 11:09:53 [crit] 2539#0: *15 connect() to unix:/tmp/php-fpm.sock failed (13: Permission denied) while connecting to upstream, client: 127.0.0.1, server: www.example.com, request: "GET /foo HTTP/1.1", upstream: "fastcgi://unix:/tmp/php-fpm.sock:", host: "www.example.com"
SOLUTION
The problem was solved after the following lines were un-commented in the file, /etc/php5/fpm/pool.d/www.conf
listen.owner = www-data listen.group = www-data
The same file, /etc/php5/fpm/pool.d/www.conf, had the lines
user = www-data group = www-data
Also, the nginx configuration file /etc/nginx/nginx.conf had the user and group settings,
user www-data www-data;
