Cannot access Mysql DB as root using phpmyadmin - mysql

Question

I have this docker-compose file:
version: "3"
services:
db:
image: mysql/mysql-server:5.7
container_name: mysqldb
restart: always
environment:
MYSQL_ROOT_PASSWORD: 4dfLtRah2C
MYSQL_DATABASE: db
MYSQL_PASSWORD: le562BplPk
MYSQL_USER: db_user
networks:
- backend
volumes:
- ./db_data:/var/lib/mysql
phpmyadmin:
container_name: phpmyadmin
depends_on:
- db
image: phpmyadmin/phpmyadmin
restart: always
ports:
- '9006:80'
environment:
MYSQL_ROOT_PASSWORD: 4dfLtRah2C
PMA_PORT: 3306
PMA_HOST: db
networks:
- backend
networks:
backend:
When I try to use the db_user with the MYSQL_PASSWORD it works, but when I try to login as the root user and use the MYSQL_ROOT_PASSWORD it does not work, gives me a connection refused error.
I can login in to the db via the container using mysql -u root --password=$MYSQL_ROOT_PASSWORD and it works just fine...
Already tried to do docker system prune -f -a --volumes as well as removing the db_data folder multiple times to ensure that the container runs as a fresh instance.
How may I fix this? What is wrong?

Answer 1

The problem here was that phpmyadmin was trying to use root#localhost, but we want to use root#db, to fix this we simply need to perform a few modifications on the database, in order to change the host of the user root to %, like this:
(inside the db container: mysql -u root -p)
use mysql;
UPDATE mysql.user SET host='%' WHERE host='localhost' AND user='root';
FLUSH privileges;
exit;
Now I can use phpmyadmin to manage all the databases using root.
Please note that you should not abuse the root user use, instead try to use the dedicated user for your specific database, but as this is a development environment and everything is containerized no harm should come from using root.