Moving wp-config.php one level up – 500 error – Nginx [closed]

In this answer, I assume the following, going by your question:

• Your WordPress site is at /var/www/html
• Your WordPress sites’s full config file is at /var/www/wp-config.php
• There is a small file at /var/www/html/wp-config.php that (ideally) will load /var/www/wp-config.php
• Your /var/www/wp-config.php contains all the necessary content to run your WordPress site (ie, the code from wp-config-sample.php, updated as appropriate with your DB information, etc).
• There are no other WordPress installations in /var/www/*

Given all that, your /var/www/html/wp-config.php file should contain the following:

<?php

/** Absolute path to the WordPress directory. */
if ( !defined('ABSPATH') )
    define('ABSPATH', dirname(__FILE__) . "https://wordpress.stackexchange.com/");

/** Location of your WordPress configuration. */
require_once(ABSPATH . '../wp-config.php');

or

/** Absolute path to the WordPress directory. */
if ( !defined('ABSPATH') )
    define('ABSPATH', dirname(__FILE__) . "https://wordpress.stackexchange.com/");

/** Location of your WordPress configuration. */
require_once(ABSPATH . '/var/www/wp-config.php');

From your /var/www/html directory, the path ../var/www/wp-config.php is looking for /var/www/var/www/wp-config.php, which presumably doesn’t exist.

Update

The error message: failed to open stream: Permission denied indicates that your webserver can’t read the /var/www/wp-config.php file. It will at least need to read the file in order to open it.

I’d recommend asking your host to fix the permissions, or ask them how you can do it yourself. If you’re self-hosting on a *nix VPS or something similar, you’ll be looking for the chown and/or chmod commands.