Docker Series — Part 4: Exposing Containers, Setting Up MySQL, and Managing Environment Variables

Welcome to Part 4 of the Docker: Basics to Advance series.
This post is all about moving deeper into container networking, launching services like Apache Server and MySQL, and using environment variables to configure containers in a real-world DevOps setup.

Docker Deep Dive: Container Stats & Management

Let’s start with a few critical Docker commands that help you inspect and manage containers:

Understanding Container Networking

• Docker automatically assigns a private IP to every container.

• By default, containers can communicate with the host system.

• But for the outside world to access a container (like a website), we need to expose a port.

What is a Port?

Each running service listens on a unique port number (e.g., 80 for HTTP, 3306 for MySQL).
Check ports on your system with:

netstat -tnlp

Exposing a Container to the World (Using Apache Example)

To let the public access your containerized app:

Required:

• Expose the port (-p flag)

• Start services inside the container

• Use a public IP + port combination to access

Example: Launching Apache in Detached Mode

docker run -dit --name web1 -p 8080:80 httpd

This launches an Apache server container and maps its internal port 80 to host port 8080.

Verify:

Access via browser or:

curl http://<host-ip>:8080

More Useful Docker Commands

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Bonus Tip: Variables in Linux

In Linux, we can define user-defined variables using export or VAR=value.
This concept is used while passing environment variables to Docker containers too.

Running MySQL Containers with Environment Variables

Some Docker images (like MySQL) require environment variables to configure the database.

Basic MySQL Container with Root Password

docker run -dit --name db1 -e MYSQL_ROOT_PASSWORD=redhat mysql

Enter MySQL Container & Connect:

docker exec -it db1 bash
mysql -u root -p
# Enter password: redhat

Once inside MySQL:

SHOW DATABASES;

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Creating a General MySQL User with Full Config

Here’s how to create a non-root user and a database at launch:

docker run -dit --name db123 \
-e MYSQL_ROOT_PASSWORD=redhat \
-e MYSQL_USER=vimal \
-e MYSQL_PASSWORD=redhat \
-e MYSQL_DATABASE=lwstudent \
mysql:latest

Connect with General User:

docker exec -it db123 bash
mysql -u vimal -p
# Enter password: redhat

Now you can manage databases as the general user!

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Final Thoughts

In this blog, we unlocked container exposure, volume mounting, port mapping, environment variables, and real-world database deployment using Docker — all crucial pieces of any scalable DevOps infrastructure.

You're not just running containers anymore — you're now building real-world services inside Docker

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