Master Dockerfile and Docker‑Compose: Build Custom Images and Orchestrate Containers

Dockerfile Image Creation

In Docker or Podman, an image is the foundation of a container. When official images from Docker Hub cannot meet business needs, a custom image must be built using a Dockerfile.

A Dockerfile is a plain‑text file that contains a series of instructions, each creating a new layer in the image. Fewer instructions produce smaller images.

Basic Instructions

FROM – specifies the base image (only one per Dockerfile).

LABEL – adds metadata such as version or maintainer.

RUN – executes shell commands inside the image; combine multiple commands with && or line‑continuation \ to avoid extra layers.

WORKDIR – sets the working directory (similar to cd).

ADD – copies files from the host and can automatically extract archives.

COPY – copies files or directories without extraction.

ENV – defines environment variables.

CMD – the default command executed when a container starts (can be overridden).

Example: Build a Django Image

mkdir /home/docker && cd /home/docker
touch Dockerfile run.sh sources.list
# edit sources.list to use a domestic Ubuntu mirror
# download Django source
wget -O Django-3.2.5.tar.gz https://gitee.com/mirrors/django/archive/3.2.5.tar.gz
# Dockerfile content (simplified)
FROM ubuntu:20.04
LABEL version="3.2.5" maintainer="[email protected]"
ADD Django-3.2.5.tar.gz /opt/
COPY sources.list /etc/apt/sources.list
RUN apt update && apt install -y python3 python3-pip
WORKDIR /opt/
RUN mv django-3.2.5 django
WORKDIR /opt/django
RUN python3 setup.py install
WORKDIR /opt
RUN django-admin.py startproject djdemo
COPY run.sh /opt/djdemo/run.sh
WORKDIR /opt/djdemo
RUN sed -i "s/ALLOWED_HOSTS = \[\]/ALLOWED_HOSTS = \['*'\]/g" djdemo/settings.py && chmod 755 run.sh
EXPOSE 8000
CMD ["/bin/sh", "run.sh"]
# run.sh content
python3 manage.py runserver 0.0.0.0:8000
# Build and run
sudo docker build -t djdemo:3.2.5 .
docker run -d -p 8008:8000 --name=django1 djdemo:3.2.5

After building, the new image can be listed with docker images and run with port mapping.

Docker‑Compose Container Orchestration

Docker‑Compose lets you define multiple services in a single docker-compose.yml file and manage them as a project.

Installation

# Linux example
sudo curl -L "https://github.com/docker/compose/releases/download/v2.10.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose
sudo ln -s /usr/local/bin/docker-compose /usr/bin/docker-compose

Check version with docker-compose version. Remove with

sudo rm /usr/local/bin/docker-compose /usr/bin/docker-compose

.

Common Commands

docker-compose up [-d]

– start all services (detached with -d). docker-compose down – stop and remove containers, networks, and volumes. docker-compose logs [-f] – view logs. docker-compose build – (re)build images. docker-compose pull – pull service images. docker-compose ps – list containers. docker-compose exec SERVICE CMD – run a command in a running container.

Compose File Basics

A typical file includes version , services , and optional networks . Example for three Ubuntu containers:

version: "3.8"
services:
  ubuntu1:
    image: ubuntu:20.04
    container_name: "ubuntu1"
    networks: [dev]
  ubuntu2:
    image: ubuntu:20.04
    container_name: "ubuntu2"
    networks: [dev, pro]
  ubuntu3:
    image: ubuntu:20.04
    container_name: "ubuntu3"
    networks: [pro]
networks:
  dev:
    driver: bridge
  pro:
    driver: bridge

Start with docker-compose up, list with docker-compose ps, and stop with docker-compose down.

Key Service Options

image – base image name (e.g., ubuntu:20.04).

build – path to a Dockerfile to build a custom image.

command – overrides the default command.

container_name – explicit container name.

restart – restart policy (e.g., always).

environment – list of environment variables.

depends_on – defines startup order.

ports – host:container port mapping (use quoted strings to avoid YAML parsing issues).

volumes – mount host paths or named volumes.

dns – custom DNS servers.

expose – expose ports internally without publishing.

links – legacy linking between services.

net – network mode (bridge, host, none).

Real‑World Example: Multiple Nginx Services

version: "3.8"
services:
  web1:
    image: nginx:1.21.4
    container_name: "web1"
    ports: ["8081:80"]
    networks: [dev]
  web2:
    image: nginx:1.21.4
    container_name: "web2"
    ports: ["8082:80"]
    networks: [dev, pro]
  web3:
    image: nginx:1.21.4
    container_name: "web3"
    ports: ["8083:80"]
    networks: [pro]
networks:
  dev:
    driver: bridge
  pro:
    driver: bridge

Start with docker-compose up -d and access the services via http://<em>host_ip</em>:8081, 8082, 8083 after opening the corresponding security‑group ports.