Docker Series - Part 13: Dockerfile Deep Dive, Compose Magic & Real-World Tomcat Deployment

Welcome back to the Docker Zero to Advance series! In this session, we go full-throttle into real-world Docker applications. From launching Tomcat servers to automating builds with Dockerfile and Compose, we explore Docker in action with system-level control. If you're aiming to become confident with production-grade containers, this article is a must-read.

Installing Tomcat via Docker

When an image is not available locally, Docker automatically pulls it from Docker Hub.

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

Understanding Container Access

• docker attach works if the container has a shell.

• docker exec -it <container_id> bash allows access to containers even without shell support.

Tomcat Web Page Hosting

Tomcat serves files from /usr/local/tomcat/webapps/ROOT/. Place your index.html here to serve custom content.

Creating Custom Tomcat Image

FROM tomcat:9.0
RUN mkdir /usr/local/tomcat/webapps/ROOT
COPY index.html /usr/local/tomcat/webapps/ROOT/

Build it:

docker build -t mytomcat:v1 .
docker run -dit mytomcat:v1

Verify with:

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

Docker-Compose Integration

Docker Compose simplifies multi-container orchestration. It can build and launch containers from Dockerfiles.

version: "3"
services:
  webapp:
    build: .
    ports:
      - "8081:8080"

Run with:

docker-compose up -d

COPY vs ADD in Dockerfile

COPY only supports local file copying. ADD supports both file copy and URL-based downloading or extracting TAR files.

FROM centos:7
ADD https://raw.githubusercontent.com/.../README.md /

Working with TAR Files

• Create TAR: tar -cf myweb.tar /website

• Extract TAR: tar -xf myweb.tar

Add TAR into image and extract it:

FROM centos:7
ADD myweb.tar /

Docker automatically extracts the archive during build.

Apache Web Server Image

FROM centos:7
RUN yum install httpd -y
COPY *.html /var/www/html/
EXPOSE 80
ENTRYPOINT ["httpd"]
CMD ["-DFOREGROUND"]

Launch:

docker run -dit -P myweb:v1

Access using exposed random port.

ENV Variables in Dockerfile

ENV NAME=vimal

Use inside the container:

echo $NAME

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Final Thoughts: In this session, we touched on every vital Docker skill: building images, layering, running containers with Compose, exposing services, managing static files, and even working with compressed content. You're now ready to build, package, and deploy Dockerized web applications like a pro.