Warning: mysqli_real_connect(): (HY000/1698): Access denied for user 'root'#'localhost' - Docker - wordpress

Question

I'm attempting to bring a Docker image of Wordpress up with supervisor only struggling. The code is from a reputable source:
https://github.com/how2dock/docbook/tree/master/ch01/supervisor
Here's my Dockerfile
FROM ubuntu:19.04
ARG DEBIAN_FRONTEND=noninteractive
RUN apt-get update && apt-get -y install \
apache2 \
php7.2 \
php7.2-mysql \
supervisor \
wget
RUN echo 'mysql-server mysql-server/root_password password root' | debconf-set-selections && \
echo 'mysql-server mysql-server/root_password_again password root' | debconf-set-selections
RUN apt-get install -qqy mariadb-server
RUN wget http://wordpress.org/latest.tar.gz && \
tar xzvf latest.tar.gz && \
cp -R ./wordpress/* /var/www/html && \
rm /var/www/html/index.html
RUN (/usr/bin/mysqld_safe &); sleep 5; mysqladmin -u root -proot create wordpress
COPY wp-config.php /var/www/html/wp-config.php
COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf
EXPOSE 80
CMD ["/usr/bin/supervisord"]
and a portion of my wp-config.php
// ** MySQL settings - You can get this info from your web host ** //
/** The name of the database for WordPress */
define('DB_NAME', 'wordpress');
/** MySQL database username */
define('DB_USER', 'root');
/** MySQL database password */
define('DB_PASSWORD', 'root');
/** MySQL hostname */
define('DB_HOST', 'localhost');
/** Database Charset to use in creating database tables. */
define('DB_CHARSET', 'utf8');
/** The Database Collate type. Don't change this if in doubt. */
define('DB_COLLATE', '');
supervisord.conf
[supervisord]
nodaemon=true
[program:mysqld]
command=/usr/bin/mysqld_safe
autostart=true
autorestart=true
user=root
[program:httpd]
command=/bin/bash -c "rm -rf /run/httpd/* && /usr/sbin/apachectl -D FOREGROUND"
Build the container; docker build -t wordpress . and run the webserver with docker run -d -p 82:80 wordpress. Browse to http://localhost:82 expecting to find a shiny new WP install - only to find:
Access denied for user 'root'#'localhost'
I've tried several database username/password combinations. I'm a newbie to Docker. What am I missing?

Answer 1

Why you are reinventing the wheel with this Dockerfile? and also violating the rule of thumb to have single process per container?
In the case of MySQL, it not that simple to have Dockerfile and work with build time. You need to create a user at runtime using entrypoint once the MySQL service is up.
Will suggest using offical WordPress image and MySQL as simple like this.
version: '3.3'
services:
db:
image: mysql:5.7
volumes:
- db_data:/var/lib/mysql
restart: always
environment:
MYSQL_ROOT_PASSWORD: somewordpress
MYSQL_DATABASE: wordpress
MYSQL_USER: wordpress
MYSQL_PASSWORD: wordpress
wordpress:
depends_on:
- db
image: wordpress:latest
ports:
- "8000:80"
restart: always
environment:
WORDPRESS_DB_HOST: db:3306
WORDPRESS_DB_USER: wordpress
WORDPRESS_DB_PASSWORD: wordpress
WORDPRESS_DB_NAME: wordpress
volumes:
db_data: {}
Now come to your question, the reason is no user exist in your Docker container.
RUN (/usr/bin/mysqld_safe &); sleep 5; mysqladmin -u root -proot create wordpress
Each run directive executes in its own shell. so the above command will not do the job as you are expecting. you need to move these steps to entrypoint as MySQL offical dockerfile does.
Another suggestion, use MySQL as base image and expend as per your need, but again you need some proper entrypoint to work with MySQL. its not like WordPress or node container.