Docker

Today I learned that recursively changing the owner of a directory tree in a Dockerfile can result in some serious increase in image size. 🚛 The issue You may remember how in a previous post we used a small example to discuss layers and final image size. Well, here’s our example again, slightly modified. # Dockerfile FROM ubuntu WORKDIR /app RUN fallocate -l 100M example RUN chown 33:33 example Given that the base image weighs ~75MB, we could expect the final image to weigh ~175MB (~75 from the base image + ~100 from the big file we generated)....

In previous posts we talked about poetry and Docker images layers and I promised I would write about Docker multi-stage builds, so here we go! Note I will explain the basics of Docker multi-stage builds required to understand the post, but I won’t repeat the documentation (see further reading). ⚙️ Multi-stage builds Basically a multi-stage build allows you to sequentially use multiple images in one Dockerfile and pass data between them....

In this post, we’ll walk through Docker image layers and the caching around them from the point of view of a Docker user. I’ll assume you’re already familiar with Dockerfiles and Docker concepts in general. ✌️ The two axioms of Docker layers There are two key concepts to understand, from which everything else is deduced. Let’s call them our axioms. Axiom 1 Every instruction in a Dockerfile results in a layer1....