Follow these steps exactly to build a working MySQL 5.7 service from scratch.1. Start FreshDelete any of your previous failed MySQL services to avoid confusion and ensure the volume is clean.2. Deploy from a Custom ImageOn your Railway dashboard, click "+ New" -> "Service".Choose "Deploy from Image".In the "Image Name" field, enter exactly: mysql:5.7.44Click "Deploy". Railway will pull the image and create the service. It will likely show an error initially because it's missing its configuration.3. Configure Environment VariablesThis is the most critical step. The official MySQL image needs these variables to set itself up.Go to your new MySQL service and click on the "Variables" tab.Add the following variables:MYSQL_ROOT_PASSWORD: This is mandatory. Set a strong, secure password here. The service will not start without it.MYSQL_DATABASE: This is highly recommended. Set the name for your application's database (e.g., mydatabase). The container will create this empty database for you on its first run.4. Attach a Volume for Data StorageA database needs its data to be permanent. You must attach a volume.Go to the "Settings" tab of your MySQL service.Scroll down to the "Volumes" section.Click "Add Volume" and set the "Mount Path" to: /var/lib/mysqlThis is the standard directory where MySQL stores its data files.5. Connect Your Java AppOnce you add the variables and volume, your MySQL 5.7 service will redeploy and start correctly. Now you can connect your Java application.Go to your Java service's settings.Railway automatically provides environment variables to connect to other services in the project. The ones you need will be named MYSQLHOST, MYSQLPORT, MYSQLUSER (which will be root), MYSQLPASSWORD, and MYSQLDATABASE.Ensure your Java application's database connection string is configured to read these variables from the environment.By following this custom image approach, you bypass the incompatible MySQL 8 template and build the exact service you need. This will resolve the connection issues.

Part 1: Fixing the "Data Directory Has Files" ErrorThis error is happening because a previously failed deployment left some files in the volume. When MySQL tries to start again, its initialization script sees those files and aborts to avoid overwriting data. Wiping the volume can sometimes fail to clear it properly if it's still attached.We need to force a completely clean slate. Follow these steps exactly:Detach the Volume:Go to your MySQL service Settings -> Volumes.Find the attached volume and click the "Detach" button (or a similar detach/remove icon).Delete the Old Volume:Now go to your project's main dashboard where you can see all your services. There should be a "Volumes" tab for the whole project.Find the volume you just detached and permanently delete it. This ensures the corrupted data is gone for good.Redeploy Without a Volume (Crucial Step):Go back to your MySQL service and trigger a new deployment with NO volume attached.The service should deploy successfully. It will be running in an "ephemeral" mode, meaning data will be lost on restart, but this proves the Docker image itself is working. Wait for the green "Deployment Online" check.Create and Attach a NEW Volume:Once the deployment is online, go back to Settings -> Volumes.Click "Add Volume".Create a brand new volume and set the Mount Path to /var/lib/mysql.This will trigger one final redeployment.This final deployment will now run the MySQL initialization script on a brand new, truly empty volume, and the error will be resolved.Part 2: Understanding the "Required Variables" WarningNow, let's address the issue from your first screenshot. You can and should ignore this warning.Here is the simple explanation:Your Variables (MYSQL_ROOT_PASSWORD): These are the variables the MySQL Docker image needs to set itself up for the first time. You have configured these correctly. These are the ones that matter.Railway's Variables (MYSQLHOST, MYSQLPASSWORD): These are variables that Railway generates automatically after your service is running. It creates them so your other applications can easily connect to this database.The warning in the "Data" tab is a UI feature designed for Railway's official templates. It doesn't fully understand the needs of a custom Docker image, so it shows a generic prompt. It will not stop your database from working.The second warning you saw ("Database will still use the old credentials internally") is shown because you tried to edit the generatedMYSQLPASSWORD variable. Railway is correctly telling you that changing its reference variable won't change the actual root password you set inside the database with MYSQL_ROOT_PASSWORD.In summary: Follow the "clean slate" steps in Part 1 to get your database running. The variable warning in the UI is just a notification and can be safely ignored.