Why Does 'Access Denied' Occur for the MySQL Root User Even When MYSQL_ROOT_PASSWORD Is Set in Docker?

MySQL_ROOT_PASSWORD Is Set, But Access Denied for User 'root'@'localhost' (using Password: YES)

In dockerized MySQL environments, setting the MYSQL_ROOT_PASSWORD environment variable is not sufficient to ensure access to the database. This is because the image will not initialize a new database if the db_data volume already contains an existing installation.

Troubleshooting:

1. Check if a database is already initialized in the db_data volume: If you started the container with a pre-existing volume, the environment variables will have no effect and the database will not be initialized.

2. Delete the db_data volume to force initialization:

   • Run docker-compose down -v to remove the existing volume.
   • Run docker-compose up -d to start the container with a fresh volume and initialize the database.

3. Convert to a bind mount if desired:

   • After initializing the database, you can convert the volume to a bind mount by changing the volumes section in docker-compose.yml to:

     volumes:
        - /host/path/to/db_data:/var/lib/mysql

   • Delete the contents of the bind mount location before starting the container: rm -rf /host/path/to/db_data/*

4. Check for other potential issues:

   • Ensure that the MYSQL_ROOT_PASSWORD variable is set properly.
   • Check the firewall settings to ensure that port 3306 is open.
   • Verify that the MySQL service is running within the container.

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