How to Reduce Docker Image Size

Marek Krzeszowiec

13 Nov

12 minutes

Docker is a popular containerization platform that allows developers to easily and consistently deploy software across different environments. One of the key aspects of using Docker is creating efficient container images that are not only small and portable but also secure and performant. In this article, we'll present seven practical ways to reduce the size of Docker images.

Choose the Right Base Image

Every Docker image is based on another base image, which serves as the foundation for your application. By selecting a minimal base image that includes only essential system components, you can significantly impact the size of the final image.

Minimize Image Layers

Docker relies on a layered filesystem, which means that each change to the container's filesystem creates a new layer. To reduce the image size, avoid unnecessary layering and group operations into a single layer whenever possible.

Remove Unnecessary Files

Make sure there are no unnecessary files in your image. Utilize .dockerignore to exclude files and directories that are not required during the image-building process. This helps eliminate unnecessary bloat in the image.

Optimize Image Layers

Avoid installing unnecessary packages and components. Install only the libraries and tools necessary for the proper functioning of your application. You can also remove temporary files and caches created during package installations to reduce the image size.

Use Multi-Stage Builds

Multi-stage builds involve creating temporary images for specific tasks and then copying only the essential files to the final image. This approach allows you to minimize the size of the final image while retaining intermediate images for various tasks.

Utilize Alpine-based Images

Alpine Linux-based images are known for their lightweight and container-optimized nature. Whenever possible, choose base images that are built on Alpine, as they are often much smaller than their counterparts based on other Linux distributions.

File Compression and Optimization

The final step in reducing the Docker image size involves file compression and application settings optimization. You can make use of tools like docker-slim to automate this process and assist in achieving a smaller image size.

In summary, creating efficient Docker images requires considering various factors, such as selecting the right base image, minimizing layers, removing unnecessary files, and more. With the right practices and tools, you can significantly reduce the image size, which is essential for both the performance and security of your container.