Fix WP Super Cache 'Cannot Update wp-config.php' Error

🕐 2025-02-12 ✍️ Moyi Foreign Trade

After installing the WP Super Cache plugin on a WordPress site, it may fail to work. Here is how to fix it:

Check the cache files

Go to the wp-content directory: Run cd /var/www/html/wordpress/wp-content.
Check wp-cache-config.php: If it does not exist, copy ./plugins/wp-super-cache/wp-cache-config-sample.php to the wp-content/ directory and name it wp-cache-config.php — i.e., run cp plugins/wp-super-cache/wp-cache-config-sample.php ./wp-cache-config.php.
Check advanced-cache.php: If it does not exist, copy ./plugins/wp-super-cache/advanced-cache.php to the wp-content/ directory with cp plugins/wp-super-cache/advanced-cache.php ./.

Add the configuration

Return to the WordPress root directory and add the following two lines to wp-config.php, before ABSPATH:

define('WP_CACHE', true);
define('WPCACHEHOME','/var/www/html/wordpress/wp-content/plugins/wp-super-cache/');

Save the file and revisit the admin dashboard.

Fix for "Cannot Update wp-config.php" After Installing WP Super Cache: Pre-Operation Checklist

The worst thing about technical tutorials is copying commands while ignoring environment differences. Different system versions, web servers, plugin combinations, and permission settings all affect the final result. Before you start, it is a good idea to record your current configuration and, if necessary, take a snapshot or backup. That way, even if a step goes wrong, you can roll back quickly.

Things to confirm before you start

System and software versions: Confirm the versions of Windows, Debian, Nginx, Apache, WordPress, or related tools.
Permissions: When credentials, certificates, or configuration files are involved, first confirm that your current user has sufficient permissions.
Backups: Before modifying configuration files, make a copy of the original; for WordPress sites, back up the database as well.
Testing: Verify after every change — do not wait until everything is modified to start troubleshooting.

Troubleshooting approach

When you hit an error, first figure out which layer it occurs in: browser, DNS, server, application, plugin, or permissions. Breaking the problem down is more effective than repeatedly searching for the whole error message. For issues like WordPress, Nginx, certificates, and proxies, logs are usually more reliable than the front-end page.

If the paths or menus in a tutorial do not match your environment, trust what your current system shows and locate the equivalent feature by keywords. Windows Control Panel, WordPress plugin menus, and cloud console entry points in particular often change with version updates.

Follow-up maintenance tips

Completing one fix does not mean the problem is gone forever. Keep a record of key commands, modified files, modification times, and verification results. When you later migrate servers, upgrade plugins, or change themes, these records will save you a lot of debugging time.