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Bind mounts

Learn to mount host directories with bind mounts.

Bind mount

A bind mount mounts a folder or file on the host directly into the container. The source must be a path (starting with /, ./ or $PWD). In development it's used to mount code into the container; the container sees the change the moment you save the file:

docker run -d --name web -p 8080:80 -v "$PWD/site":/usr/share/nginx/html:ro nginx
# edit site/index.html, refresh the browser

Mounting files and permissions

A single configuration file can be mounted too. In a bind mount, files carry the host's ownership and permissions; if the container runs as a non-root user, write permission problems can occur:

docker run -d -v "$PWD/nginx.conf":/etc/nginx/nginx.conf:ro nginx
docker run --rm -u "$(id -u):$(id -g)" -v "$PWD":/app -w /app node:20 npm run build

The second command makes the created files belong to your user instead of root.

Practice A site developed live

Start a container named web from nginx in the background: map host 8080 to container 80; mount the site folder in the current folder ("$PWD/site") read-only at /usr/share/nginx/html.

Starter code

terminal
# buraya yaz

Expected output

6f708192a3b4

Questions and answers

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

1 What is the main difference between a bind mount and a named volume?

  • A bind mount is more persistent
  • A volume is read-only
  • There's no difference
  • A bind mount uses a specific host path; Docker manages a volume Correct answer

Explanation: Volumes for production data and bind mounts for code in development are typical.

2 Mount the current folder at /app.

Question 
docker run --rm -v ____:/app -w /app node:20 npm test
Answer 
docker run --rm -v "$PWD":/app -w /app node:20 npm test

Explanation: $PWD is the full path of the current folder.

3 Match.

Term Meaning
-v "$PWD":/app Bind mount
-v data:/app Named volume
:ro Read-only
-u "$(id -u)" Fix for file ownership

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