How to Modify MYSQLUSER and WORDPRESSDB_USER without getting a 502 Bad Gateway Error in Docker-Compose?

Understanding WordPress Database and Docker-Compose

Hey there friend! Today, we’ll delve into the world of WordPress, Docker, and how your database plays a critical role in this environment. Let’s start with your WordPress database.

In the WordPress setup, all your site’s data – your posts, pages, comments, among other things – are stored in a database. For docker environments, we usually set up this database with some initial values. This includes your database name, username and password. These are used when creating the database for the first time. In Docker, we use a file called docker-compose.yml to help set up our environment, including our WordPress database. This file looks a bit like this:

environment:
MYSQL_ROOT_PASSWORD: mystrongpassword
MYSQL_DATABASE: wordpress
MYSQL_USER: wordpress
MYSQL_PASSWORD: wordpress

Now the part

volumes:
 - ./db_data:/var/lib/mysql

refers to something we call persistence data. This means that even when we stop our docker container (containers are like little environments where our applications run), the data (in this case, our database) remains stored and can be used again.

Now, here’s the ‘gotcha’. Once your database is set up, if you run docker-compose up again, it does not overwrite the existing data. Why? Because the data is persistent, as we discussed earlier!

So How Can You Change The Password or Other Database Information?

You have a couple of options.

Option 1: Build Anew

In this option, you’d start from scratch and build a new environment. Below are the steps you’d follow:

1. Remove the existing data (or even the whole docker image)
2. Modify the docker-compose.yml file with your new password (or any other database information)
3. Run docker-compose again to rebuild.

Option 2: Manual Change

Another approach would be to manually change the password or other database details from inside the running database container. Here’s how you can do that:

1. Start your database container
2. Log into your container. You’d do this by running a command like docker exec -it /bin/bash
3. Once inside, change the password (or any other details you need to change)
4. Logout and commit (save) your changes.

Between the two, the first option is simpler, less error-prone, and is generally the better one to choose, even though it might seem a bit more involved.

There you have it! Hoping this sheds some light on how your WordPress database interacts with Docker and what you can do when you want to change some of those initial setup values. If you have any other questions, feel free to ask! Happy WordPressing!