images VS distrobuilder

Callisto uses open-source Webdriver images (all thanks to folks from Aerokube), allowing you to focus on your tests instead of browser packaging and updates.

LXC

which is what docker/podman/containerd use. If you want full system emulation look into LXC/LXD.

LXD is a manager for Linux Containers (LXC), which lets me spin up a kind-of lightweight VM for any distro, instantly. I use it to run proprietary software isolated from the rest of my system (such as Steam); disposable environments for trying stuff out, and running software that doesn't jive well with Nixos.

Check this thread on linuxcontainers LXD forum. Half way down Simos points to the eventual solution:

I found this website https://linuxcontainers.org/ and I am going to test that out for server just to see how it works.

Up to now the best documentation I have come across is the official one at linuxcontainers.org.

Containers, like LXC or Docker.

After five years managing physical servers, then another four years working with VM clusters, the value of Linux Containers(LXC) and their eventual productization as Docker appealed to me.

Docker introduced container images to the technology world, making container images a standardized delivery unit. In fact, before Docker, containerization technology already existed. Let's talk about a more recent technology, LXC (Linux Containers) in 2008. Compared to Docker, LXC is less popular since Docker provides container images, which can be more standardized and more convenient to migrate. Also, Docker created the DockerHub public service, which has become the world's largest container image repository. In addition, containerization technology can also achieve a certain degree of resource isolation, including not only CPU, memory, and other resources isolation, but also network stack isolation, which makes it easier to deploy multiple copies of applications on the same machine.