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.
A popular base image is Debian Buster. What's in the 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/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.