Copying files to and from containers in Docker - Mini Project: Build & Apply

Copying files to and from containers

📖 Scenario: You are working with Docker containers and need to move files between your local machine and a running container. This is a common task when you want to add configuration files or retrieve logs from containers.

🎯 Goal: Learn how to copy files into a running Docker container and copy files out from it using Docker commands.

📋 What You'll Learn

Create a simple Docker container running in the background

Copy a file from the local machine into the container

Copy a file from the container back to the local machine

Verify the copied files exist in the correct locations

💡 Why This Matters

🌍 Real World

Copying files to and from containers is essential when you need to add configuration files, scripts, or retrieve logs and data from running containers.

💼 Career

DevOps engineers and developers often need to manage files inside containers for debugging, configuration, and deployment tasks.

1

Start a running container

Run a Docker container named mycontainer in detached mode using the alpine image and keep it running with the command sleep 300.

Docker

# Run the container named mycontainer in detached mode
# Your code here

Need a hint?

Use docker run -d --name mycontainer alpine sleep 300 to start the container.

2

Copy a file into the container

Create a file named hello.txt locally with the content Hello from local! and then copy this file into the container mycontainer at path /root/hello.txt using the Docker copy command.

Docker

docker run -d --name mycontainer alpine sleep 300
# Create hello.txt and copy it into the container
# Your code here

Need a hint?

Use echo to create the file and docker cp to copy it into the container.

3

Copy a file from the container to local

Inside the container mycontainer, create a file /root/containerfile.txt with content Hello from container!. Then copy this file from the container to your local machine as containerfile.txt using the Docker copy command.

Docker

docker run -d --name mycontainer alpine sleep 300

echo "Hello from local!" > hello.txt
docker cp hello.txt mycontainer:/root/hello.txt
# Create containerfile.txt inside container and copy it to local
# Your code here

Need a hint?

Use docker exec to create the file inside the container and docker cp to copy it out.

4

Verify copied files

Use cat commands to display the contents of the local files hello.txt and containerfile.txt to verify the copy operations worked correctly.

Docker

docker run -d --name mycontainer alpine sleep 300

echo "Hello from local!" > hello.txt
docker cp hello.txt mycontainer:/root/hello.txt

docker exec mycontainer sh -c 'echo "Hello from container!" > /root/containerfile.txt'
docker cp mycontainer:/root/containerfile.txt ./containerfile.txt
# Print contents of hello.txt and containerfile.txt
# Your code here

Need a hint?

Use cat hello.txt and cat containerfile.txt to see the file contents.