Well, you're always coming FROM something, unless you're coming FROM scratch, which is literally empty. A popular base image is Debian Buster. What's in the Do

Well, you're always coming FROM something, unless you're coming FROM scratch, which is literally empty. A popular base image is Debian Buster. What's in the Dockerfile? https://github.com/debuerreotype/docker-debian-artifacts/blob/17d8dadb220460bf153bf2de493c2bc873ef52de/buster/Dockerfile https://github.com/debuerreotype/docker-debian-artifacts/blo... Wow, simple, it just adds a "rootfs" archive. What's in there? https://github.com/debuerreotype/docker-debian-artifacts/blob/17d8dadb220460bf153bf2de493c2bc873ef52de/buster/rootfs.manifest https://github.com/debuerreotype/docker-debian-artifacts/blo... Aha. So what we have in rootfs.xz is essentially the output of a Debian system with all of those packages installed in it, and the minimal configuration needed to tie them together. No init system, no kernel, just a big filesystem full of the usual stuff an absolutely minimal Debian install would have. Now, when you run FROM debian:buster, what you get is a base layer with enough to be useful. `apt-get` is there with a default repository list that works fine, and you can install things to your hearts' content.