This document provides a comprehensive guide to create a secure and efficient Docker image. It will guide you through the process of creating a Docker image that is secure, efficient, and utilizes Docker layer caching to speed up the build process.
When specifying the base image for your Dockerfile, it's important to use a specific version tag, not the latest tag. This ensures that the build is repeatable and that it won't suddenly break due to changes in the base image.
FROM <BASE_IMAGE>:<VERSION>
You can also use an argument to easily switch between different versions of the image. For even greater security, consider using the SHA256 digest of the image instead of the tag. This ensures that you are always using the exact same image for each build, providing a high level of reproductability.
Not all Docker images are created equal. Some may contain vulnerabilities or be outdated. Use a tool like Snyk to scan your base image for vulnerabilities. This will help you choose a secure base image, or identify necessary security updates. This is a crucial step in ensuring that your Docker image is secure from the start.
Installing system packages manager tool like apk or apt is a common step in many Dockerfiles. This step should be cached to speed up the build process, as these packages don't change often. Be sure to clean up the package manager cache to reduce the size of the image. This step is important for optimizing the build process and keeping the image size as small as possible
For each language, we might use a different package manager.
For examples: