Deploying from CI/CD pipeline in Docker - Commands & Configuration

Introduction

Deploying from a CI/CD pipeline means automatically building and sending your app to a server or cloud when you update your code. This saves time and avoids mistakes from doing it by hand.

When you want your app to update automatically after you push code changes to your repository

When you want to build a new version of your app image and run it without manual steps

When you want to test your app in a clean environment every time you change code

When you want to avoid forgetting steps or making errors during deployment

When you want to deliver updates faster and more reliably to users

Config File - docker-compose.yml

docker-compose.yml

version: '3.8'
services:
  webapp:
    image: my-app:latest
    ports:
      - "8080:80"
    restart: always

This docker-compose.yml file defines a service named webapp that runs the my-app:latest Docker image. It maps port 8080 on your machine to port 80 inside the container, so you can access the app in a browser at localhost:8080. The restart: always ensures the container restarts automatically if it stops.

Commands

This command builds a Docker image named 'my-app' with the 'latest' tag from the current folder. It packages your app and its environment into one image.

Terminal

docker build -t my-app:latest .

Expected Output

Sending build context to Docker daemon  10.24MB

Step 1/5 : FROM python:3.10-slim

 ---> 123abc456def

Step 2/5 : COPY . /app

 ---> Using cache

Step 3/5 : WORKDIR /app

 ---> Using cache

Step 4/5 : RUN pip install -r requirements.txt

 ---> Using cache

Step 5/5 : CMD ["python", "app.py"]

 ---> Using cache

Successfully built abcdef123456

Successfully tagged my-app:latest

This command starts the services defined in the docker-compose.yml file in detached mode, running your app in the background.

Terminal

docker-compose up -d

Expected Output

Creating network "default" with the default driver

Creating webapp ... done

→

-d - Run containers in the background (detached mode)

This command lists running Docker containers so you can check if your app container is running.

Terminal

docker ps

Expected Output

CONTAINER ID   IMAGE          COMMAND                  CREATED          STATUS          PORTS                  NAMES

abcdef123456   my-app:latest  "python app.py"          10 seconds ago   Up 9 seconds    0.0.0.0:8080->80/tcp   myproject_webapp_1

This command shows the live logs of your app container so you can see what it is doing or if there are errors.

Terminal

docker-compose logs -f

Expected Output

Attaching to myproject_webapp_1

webapp_1  | Starting app...

webapp_1  | App running on port 80

→

-f - Follow log output live

Key Concept

If you remember nothing else from this pattern, remember: automate building and running your app with Docker commands in your CI/CD pipeline to deploy reliably and quickly.

Common Mistakes

Not tagging the Docker image with a consistent name and tag

The pipeline won't know which image to deploy or may deploy an old version

Always use a clear image name and tag like 'my-app:latest' or version numbers

Running 'docker-compose up' without '-d' in CI/CD

The command will block the pipeline and never finish because it runs in the foreground

Use 'docker-compose up -d' to run containers in the background

Not checking container status with 'docker ps' after deployment

You might miss that the container failed to start or crashed

Always verify running containers with 'docker ps' to confirm deployment success

Summary

Build your Docker image with 'docker build' to package your app.

Use 'docker-compose up -d' to start your app container in the background.

Check running containers with 'docker ps' to confirm deployment.

Follow logs with 'docker-compose logs -f' to monitor your app.