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.dockerignore

Learn to filter build context with .dockerignore.

.dockerignore

.dockerignore lists the files to exclude from the context with .gitignore-like patterns. The context shrinks, the build speeds up, and secret files (.env) are kept from accidentally entering the image:

# .dockerignore
.git
node_modules
*.log
.env
Dockerfile
!README.md       # ! exception: include this anyway

Why is node_modules excluded?

The local node_modules is both very large and may be compiled for the host operating system (e.g. native modules compiled on macOS don't work in a Linux container). The right way is to install the dependencies inside the image with npm ci:

COPY package*.json ./
RUN npm ci --omit=dev
COPY . .          # thanks to .dockerignore, the local node_modules doesn't come

Practice Write a .dockerignore

Write the contents of a .dockerignore for a Node.js project: exclude .git, node_modules, .env and all .log files.

Starter code

terminal
# buraya yaz

Sample solution

terminal
.git
node_modules
.env
*.log

Expected output

[+] Building 1.1s
 => [internal] load build context
 => => transferring context: 18.42kB

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What is the main reason to add the .env file to .dockerignore?

  • To speed up the build
  • To turn off environment variables
  • To delete the file
  • To keep passwords from entering the image layers Correct answer

Explanation: Anyone who pulls the image can read the files in its layers.

2 Exclude all log files.

Question 
____.log
Answer 
*.log

Explanation: * matches any sequence of characters.

3 Match the patterns.

Term Meaning
.git Version history
*.log All log files
!README.md Exception
.env Secret values

All lessons in Beginner

1 What is Docker?

  1. What is Docker?
  2. Containers and virtual machines
  3. Images and containers
  4. Docker architecture
  5. Use cases
  6. Summary - What is Docker

2 Installation and first commands

  1. Installing Docker
  2. docker version
  3. docker info
  4. The hello-world container
  5. Docker Desktop
  6. Summary - Installation

3 First container

  1. docker run basics
  2. Running in the background
  3. docker ps
  4. docker stop and rm
  5. docker logs
  6. Summary - First container

4 Dockerfile basics

  1. What is a Dockerfile?
  2. The FROM instruction
  3. The RUN instruction
  4. COPY and ADD
  5. CMD and ENTRYPOINT
  6. Summary - Dockerfile

5 Build and images

  1. docker build
  2. Tagging images
  3. Build context
  4. Layers and cache
  5. .dockerignore
  6. Summary - Build

6 docker run options

  1. Interactive mode
  2. Naming containers
  3. Restart policy
  4. Working directory
  5. Switching users
  6. Summary - docker run

7 Image management

  1. docker images
  2. docker rmi
  3. docker pull
  4. docker push
  5. docker tag
  6. Summary - Image management

8 Port mapping

  1. The port concept
  2. The -p flag
  3. Multiple ports
  4. Random ports
  5. IP binding
  6. Summary - Port mapping

9 Volumes and data

  1. Data persistence
  2. Named volumes
  3. The -v flag
  4. Bind mounts
  5. Volume management
  6. Summary - Volumes

10 Environment variables

  1. The -e flag
  2. The ENV instruction
  3. The ARG instruction
  4. env-file
  5. The WORKDIR instruction
  6. Summary - Environment

11 Project: docker-compose

  1. Compose design
  2. Service definition
  3. Database service
  4. Volume and network
  5. Putting it together - compose

12 Docker Hub and registry

  1. What is Docker Hub?
  2. docker login
  3. Searching images
  4. Official images
  5. Private registry
  6. Summary - Registry

13 Network basics

  1. Network drivers
  2. docker network ls
  3. Bridge network
  4. Container connectivity
  5. Publishing ports
  6. Summary - Network

14 Beginner final

  1. Challenge - Dockerfile
  2. Challenge - Build and run
  3. Challenge - Volume
  4. Challenge - Compose
  5. Challenge - Beginner project