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Working directory

Learn to set the working directory with -w.

Working directory

-w (--workdir) sets the starting directory for the process inside the container; it overrides WORKDIR from the Dockerfile. It is widely used to mount a folder and run a command there:

docker run --rm -w /tmp alpine pwd
# /tmp
docker run --rm -v "$PWD":/src -w /src node:20 npm install

The second command runs npm install in the project folder on the host without installing Node.

Overriding image settings

docker run can override most of the settings in the image: the command (arguments after the image), the working directory (-w), the entry point (--entrypoint), the user (-u) and environment variables (-e). Replacing the entrypoint with a shell to look inside an image is common:

docker run --rm -it --entrypoint sh api:1.0

Practice Run a tool in the project

Write the command for a container, deleted when done, that mounts the current folder ("$PWD") at /src in the container, sets the working directory to /src and runs npm test in the node:20 image.

Starter code

terminal
# buraya yaz

Expected output

> api@1.0.0 test
> node --test
# pass 12
# fail 0

Questions and answers

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

1 With WORKDIR /app in the Dockerfile, what does docker run -w /data img pwd print?

  • /
  • It errors
  • /data Correct answer
  • /app

Explanation: Run-time options override image settings.

2 Replace the image's entry point with a shell.

Question 
docker run --rm -it ____ sh api:1.0
Answer 
docker run --rm -it --entrypoint sh api:1.0

Explanation: --entrypoint overrides the ENTRYPOINT instruction.

3 Match.

Term Meaning
-w Working directory
--entrypoint Entry point
-u User
arguments after the image Command

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