How to Configure Redis Object Cache for WordPress on a Linux Server

ByAkensai

Learning how to configure Redis object cache for WordPress on a Linux server is one of the best performance upgrades you can make. WordPress makes a lot of database queries on every page load. Without caching, those queries run repeatedly , even for identical data. Redis stores that data in memory. Your server returns cached results instead of hitting the database every time. The result is faster page loads, lower CPU usage, and a better experience for your visitors. In this tutorial, you’ll install Redis on Ubuntu, connect it to WordPress using the Redis Object Cache plugin, and verify that everything works correctly.

Prerequisites for Configuring Redis Object Cache for WordPress on a Linux Server

Before you start, make sure your setup meets these requirements:

– Operating System: Ubuntu 20.04 or 22.04 LTS (commands also work on Debian)
– Web Server: Apache or Nginx with PHP 7.4 or higher
– WordPress: A working WordPress installation with admin access
– Server Access: SSH access with sudo privileges
– PHP Extension: The php-redis extension must be installable
– Estimated Time: 20–30 minutes

You should be comfortable running commands in a terminal. You don’t need to be an expert, but basic Linux navigation helps. Make sure your WordPress site is live and accessible before you begin. Take a full backup of your site and database before making server-level changes. This protects you if anything goes wrong during the process.

How to Configure Redis Object Cache for WordPress on a Linux Server: Step-by-Step

This event shares similarities with: How to Set Up Ssh Key Authentication on Linux Servers

Follow these steps carefully. Each one builds on the previous.

Step 1: Update your package list

Always update your packages before installing new software. This ensures you get the latest stable versions.

sudo apt update && sudo apt upgrade -y

Step 2: Install Redis Server

Install the Redis server package from Ubuntu’s official repositories.

sudo apt install redis-server -y

After installation, start Redis and enable it to run on boot.

sudo systemctl start redis-server
sudo systemctl enable redis-server

Confirm Redis is running with this command:

sudo systemctl status redis-server

You should see active (running) in the output.

Step 3: Test the Redis connection

Run a quick ping test to confirm Redis responds correctly.

redis-cli ping

Redis should reply with PONG. If it does, the server is working.

Step 4: Install the PHP Redis extension

WordPress needs the PHP Redis extension to communicate with the Redis server. Install it with this command:

sudo apt install php-redis -y

After installing, restart your web server. Use the correct command for your setup:

For Apache:

sudo systemctl restart apache2

For Nginx with PHP-FPM (replace 8.1 with your PHP version):

sudo systemctl restart php8.1-fpm
sudo systemctl restart nginx

Verify the extension loaded correctly:

php -m | grep redis

You should see redis in the output.

Step 5: Configure Redis to use a Unix socket (optional but recommended)

Using a Unix socket instead of TCP is faster for local connections. Open the Redis config file:

sudo nano /etc/redis/redis.conf

Find and update these lines:

unixsocket /var/run/redis/redis-server.sock
unixsocketperm 770

Also set a memory limit to prevent Redis from consuming all available RAM:

maxmemory 256mb
maxmemory-policy allkeys-lru

Save the file and restart Redis:

sudo systemctl restart redis-server

Add your web server user to the Redis group so it can access the socket:

For Apache:

sudo usermod -aG redis www-data

For Nginx:

sudo usermod -aG redis www-data

Step 6: Add Redis settings to wp-config.php

Open your WordPress configuration file:

sudo nano /var/www/html/wp-config.php

Add these lines above the line that says / That's all, stop editing! /:

define('WP_REDIS_HOST', '127.0.0.1');
define('WP_REDIS_PORT', 6379);
define('WP_REDIS_TIMEOUT', 1);
define('WP_REDIS_READ_TIMEOUT', 1);
define('WP_REDIS_DATABASE', 0);

If you configured a Unix socket in Step 5, use this instead:

define('WP_REDIS_SCHEME', 'unix');
define('WP_REDIS_PATH', '/var/run/redis/redis-server.sock');

Save the file.

Step 7: Install the Redis Object Cache plugin

Log in to your WordPress admin dashboard. Go to Plugins → Add New and search for Redis Object Cache. Install and activate the plugin by Till Krüss. You can also find it on the official WordPress plugin repository.

Step 8: Enable the object cache

Go to Settings → Redis in your WordPress dashboard. You’ll see a status panel. Click Enable Object Cache. The plugin creates a object-cache.php drop-in file in your wp-content directory. The status should change to Connected.

Troubleshooting Redis Object Cache Issues on Linux

Things don’t always go smoothly. Here are the most common problems and how to fix them.

Status shows “Not Connected”

Check that Redis is actually running:

sudo systemctl status redis-server

Also verify your wp-config.php settings match your Redis configuration. A typo in the host or port will break the connection.

Permission denied on Unix socket

If you used a Unix socket, confirm the web server user belongs to the Redis group:

groups www-data

You should see redis listed. If not, re-run the usermod command and restart your web server.

PHP Redis extension not loading

Run php -m | grep redis again. If nothing appears, the extension may not have installed correctly. Try reinstalling:

sudo apt install --reinstall php-redis -y

Then restart your web server.

Redis using too much memory

Check memory usage with:

redis-cli info memory

If usage is high, reduce the maxmemory value in /etc/redis/redis.conf and restart Redis.

Object cache drop-in conflict

Some caching plugins install their own object-cache.php file. This conflicts with the Redis plugin. Deactivate other caching plugins before enabling Redis Object Cache. Check the official Redis documentation for advanced configuration options if needed.

Conclusion

You now know how to configure Redis object cache for WordPress on a Linux server from start to finish. You installed Redis, added the PHP extension, updated wp-config.php, and connected WordPress through the Redis Object Cache plugin. Your site now stores database query results in memory. This cuts response times and reduces load on your MySQL database. The difference is especially noticeable on high-traffic sites or those with complex queries.

From here, you can explore adding Redis-based session storage or combining Redis with a full-page cache plugin for even better results. Monitor your Redis memory usage regularly using redis-cli info to keep things running smoothly.

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