How to See Docker Image Contents

TLDR

To see what's inside a Docker image, use docker run with an interactive shell, or inspect layers with docker history and docker image inspect. This helps you debug, verify, or explore images before running them.

Prerequisites

• Docker installed
• Terminal access

Start a Shell Inside the Image

The most direct way to explore an image is to start a container with an interactive shell. This lets you browse files and directories as if you were inside a running system.

# Start a shell in the image (replace with your image name)
docker run --rm -it nginx:alpine sh

Now you can use commands like ls, cat, or find to look around. This is great for checking configuration files or installed binaries.

Inspect Image Layers and Metadata

You can see the history of how an image was built and its metadata using these commands:

# Show the image build history
docker history nginx:alpine

# Inspect detailed metadata
docker image inspect nginx:alpine

This gives you insight into each layer and the commands used to build the image.

Extract Files Without Running a Container

If you want to extract files from an image without running it, you can use a temporary container and the docker cp command:

# Create a stopped container from the image
container_id=$(docker create nginx:alpine)

# Copy a file or directory from the container
docker cp $container_id:/etc/nginx/nginx.conf ./nginx.conf

# Remove the temporary container
docker rm $container_id

This is handy for debugging or retrieving configuration files.

Next Steps

Try exploring different images, or automate these checks in your CI pipeline to catch issues early.

Good luck with your project!