How to use Docker Image History to analyze and optimize image layers?

The docker history command is an indispensable tool for deep analysis of the structure of a ready-made Docker image and finding opportunities for its optimization. Each step in a Dockerfile creates a separate immutable layer, which leads to an increase in the final weight of the application if the build is performed incorrectly. Image history allows you to study in detail the contribution of each instruction to the total size.

For analysis, it is enough to run the docker history command specifying the image name and tag. The output will display a list of all layers, their unique identifiers, creation time, and the size of each individual component. Special attention should be paid to layers with non-zero size that appeared as a result of executing file copy commands, package installations, or archive downloads.

Based on the obtained data, redundant operations can be identified, such as installing temporary utilities without subsequently removing them in the same layer. Understanding the layer structure helps to correctly apply multi-stage builds and combine commands via logical AND operators, which dramatically reduces the size of the final artifact and speeds up its download to the registry.