Chapter 6: Why Docker, Images and How a Container Is Created

6.8 nginx, PHP and MySQL — three containers, three jobs

By Ravindra Bagale Last updated: 25 October 2026

Suppose we are building the badge for real, still on one laptop or one lab EC2. Three official images, three roles:

Container	Official image	Role
`badge-nginx`	`nginx`	Front door. The browser talks only to nginx.
`badge-php`	`php:8-apache`	Runs the badge PHP.
`badge-mysql`	`mysql`	Stores badge rows. Data must survive a container delete.

They share one user-defined network so PHP can open badge-mysql by name. Chapter 7 is where bridge, host, none, overlay and macvlan are named, and where named, bind, tmpfs and anonymous volumes are compared. The commands below are the picture. The password is a lab placeholder. It is not a real secret. Do not commit it. Do not copy it onto a client server.

Save badge-nginx.conf next to your shell. Nginx sends each request to the PHP container by name:

server {
    listen 80;
    location / {
        proxy_pass http://badge-php:80;
    }
}

docker network create badge-net

docker volume create badge-mysql-data

docker run -d --name badge-mysql --network badge-net \
  -e MYSQL_ROOT_PASSWORD=lab-only-change-me \
  -e MYSQL_DATABASE=badge \
  -v badge-mysql-data:/var/lib/mysql \
  mysql

docker run -d --name badge-php --network badge-net \
  -p 8081:80 \
  -e MYSQL_HOST=badge-mysql \
  -e MYSQL_PASSWORD=lab-only-change-me \
  badge-php:1.0

docker run -d --name badge-nginx --network badge-net \
  -p 8080:80 \
  -v "$PWD/badge-nginx.conf:/etc/nginx/conf.d/default.conf:ro" \
  nginx

MySQL writes its files under /var/lib/mysql inside the container. The named volume keeps those files when you docker rm badge-mysql and start a new container with the same -v. Without it, removing the container removes the badge rows. Do not publish 3306 on a public EC2. PHP reaches MySQL on the private network.

What you see

docker ps lists three names, all Up. MySQL can take half a minute. docker logs badge-mysql should end on a ready line, not a restart loop.
curl http://127.0.0.1:8081/ hits PHP directly.
curl http://127.0.0.1:8080/ returns the PHP text when badge-nginx.conf is mounted. Stock nginx without that file shows its own welcome page.
docker exec badge-php getent hosts badge-mysql prints an address and the name badge-mysql.

If badge-php:1.0 is missing, do section 6.5 first. If the name badge-nginx is already taken, docker rm -f badge-nginx that old container, then run it again on badge-net.

Steps — prove the three roles

Build badge-php:1.0 if you have not (section 6.5).
Create the network and the volume, then start MySQL, PHP and nginx with the commands above.
docker ps — three rows.
docker logs badge-mysql — wait until it is ready, not restarting.
curl http://127.0.0.1:8081/ — PHP text.
docker exec badge-php getent hosts badge-mysql — a name, not an error.
curl http://127.0.0.1:8080/ — the PHP text through nginx, not the nginx welcome page.
docker stop badge-mysql badge-php badge-nginx when you stop for the day. Leave the volume if you care about the lab data.

Placeholders stay out of Git

lab-only-change-me marks a lab password. Never commit a real database password, and do not copy this placeholder onto a client server.

Ravi Sir's Cards for this lesson

Nginx, PHP and MySQL: three containers, three jobs. Putting everything in one container makes it hard to update or scale.

Revision card Why one process per container? Each part can be updated, scaled and restarted alone, and logs stay clear.

Interview card

मराठी cards