ALERT: THIS NOTE APPLIES ONLY TO THE "includes/local/configure.php"
THIS DOES *NOT* APPLY TO either /includes/configure.php FILE!!!!!!

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If you're running a debugging copy of your store in your localhost environment and using the /YOUR_ADMIN/includes/local/configure.php override, there's a teeny gotcha (not present in the /includes/local/configure.php override in your storefront).

When the directory constant DIR_FS_ADMIN is generated, it's assumed that the configure.php file is in the /includes directory:
Code:
define('DIR_FS_ADMIN', realpath(dirname(__FILE__) . '/../') . '/');
Unfortunately, it's one directory step down so that the DIR_FS_ADMIN constant winds up being /YOUR_ADMIN/includes/ instead of /YOUR_ADMIN/. Anyway, the correction is to go back another directory level:
Code:
define('DIR_FS_ADMIN', realpath(dirname(__FILE__) . '/../../') . '/');