Copying files from Docker container to host

Docker, with its lightweight containers and powerful features, has transformed the way we build and deploy applications. However, managing files within a Docker container and transferring them to the host machine might seem like a daunting task for Docker newcomers. In this blog post, we’ll demystify the process, focusing on the minimalist BusyBox image.

Understanding File Transfer in Docker

Docker containers are designed to be isolated, but there are occasions when you need to move files between a container and the host machine. BusyBox, a compact and versatile Linux distribution, provides an excellent platform for understanding this process.

Step 1: Create a Dockerfile

Let’s start by creating a Dockerfile that includes BusyBox and a sample file we want to transfer.

# Use BusyBox as the base image
FROM busybox

# Create a sample file in the container
RUN echo "Hello, Docker!" > /app/sample.txt

This Dockerfile creates a file named sample.txt with the content “Hello, Docker!” in the /app directory of the BusyBox container.

Step 2: Build the Docker Image

Navigate to the directory containing your Dockerfile and execute the following command to build the Docker image:

docker build -t my-busybox-app .

This command instructs Docker to build an image named my-busybox-app using the specified Dockerfile.

Step 3: Run the Docker Container

Now, run a container based on the newly created image:

docker run --name my-container my-busybox-app

This command starts a container named my-container based on the my-busybox-app image.

Step 4: Copying Files from Container to Host

To copy the sample.txt file from the container to the host machine, use the docker cp command. Open a new terminal window and execute:

docker cp my-container:/app/sample.txt ./host-directory

Replace ./host-directory with the path on your host machine where you want to copy the file.

Congratulations! You’ve successfully transferred a file from a Docker container to your host machine using BusyBox.