How Container Filesystem Works: Building a Docker-Like Container from Scratch
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Re: How Container Filesystem Works: Building a Docker-Like Container from Scratch
#2We had chroot since 1979, nobody managed to build a docker like wrapper for chroot which do not require netns?
Re: How Container Filesystem Works: Building a Docker-Like Container from Scratch
#3We had chroot since 1979, nobody managed to build a docker like wrapper for chroot which do not require netns?
Chroot has significantly less isolation than Linux namespaces as used by Docker.
Re: How Container Filesystem Works: Building a Docker-Like Container from Scratch
#4We had chroot since 1979, nobody managed to build a docker like wrapper for chroot which do not require netns?
FreeBSD has had jails since version 4 (~year 2000), fwiw.
Much of the technology was there, but Docker was able to achieve a critical mass, with streamlined workflows. Perhaps as much a social phenomenon as a technical one?
Re: How Container Filesystem Works: Building a Docker-Like Container from Scratch
#5We had chroot since 1979, nobody managed to build a docker like wrapper for chroot which do not require netns?
Docker is a genius idea which looks obvious in retrospect, but someone need to invent it.
Docker is more than just chroot. You also need: overlay file system; OCI registry and community behind it, to create thousands of useful images. And, of course, the whole idea of creating images layer by layer and using immutable images to spawn mutable containers.
I don't actually think that you need network or process isolation. In terms of isolation, chroot is enough for most practical needs. Network and process isolations are nice to have, but they are not essential.
Re: How Container Filesystem Works: Building a Docker-Like Container from Scratch
#6We had chroot since 1979, nobody managed to build a docker like wrapper for chroot which do not require netns?
FreeBSD has had jails since version 4 (~year 2000), fwiw. Much of the technology was there, but Docker was able to achieve a critical mass, with streamlined workflows. Perhaps as much a social phenomenon as a technical one?
I think the real genius of Docker was the image packaging. The pieces were there but delivery and scripting it all wasn't easy.
Re: How Container Filesystem Works: Building a Docker-Like Container from Scratch
#7We had chroot since 1979, nobody managed to build a docker like wrapper for chroot which do not require netns?
Docker is a genius idea which looks obvious in retrospect, but someone need to invent it. Docker is more than just chroot. You also need: overlay file system; OCI registry and community behind it, to create thousands of useful images. And, of course, the whole idea of creating images layer by layer and using immutable images to spawn mutable containers. I don't actually think that you need network or process isolatio…
network isolation is very important too, that’s what lets people run 4 containers all listening on port 80
process isolation is less prominent
Re: How Container Filesystem Works: Building a Docker-Like Container from Scratch
#8Earlier quoted context omitted.
FreeBSD has had jails since version 4 (~year 2000), fwiw. Much of the technology was there, but Docker was able to achieve a critical mass, with streamlined workflows. Perhaps as much a social phenomenon as a technical one?
I think the real genius of Docker was the image packaging. The pieces were there but delivery and scripting it all wasn't easy.
BSD jails were no harder to automate than Docker; setup many ci/cd pipelines into jails in the 00s for a variety of applications.
They're way closer to the usual "Unix" tool feel too. Docker feels 100% like an attempt to get rich by engineering a monolith rather than be a few helper C tools. Docker was so annoying to learn.
Fortunately with the end of ZIRP and SaaS deflation (in real user terms, not fake investment to project we still live in the 2010s heyday), software engineers are focused on engineering more than hype generation. Am excited about energy based models, capture of electromagnetic geometry of the machine as it runs programs.
60s style lexical state management systems dragged forward in time because of social momentum have little to do with engineering. Are hardly high tech in 2025.
Re: How Container Filesystem Works: Building a Docker-Like Container from Scratch
#9We had chroot since 1979, nobody managed to build a docker like wrapper for chroot which do not require netns?
Solaris Zones (follow on to Solaris Containers) was pretty amazing.
Re: How Container Filesystem Works: Building a Docker-Like Container from Scratch
#10We had chroot since 1979, nobody managed to build a docker like wrapper for chroot which do not require netns?
FreeBSD has had jails since version 4 (~year 2000), fwiw. Much of the technology was there, but Docker was able to achieve a critical mass, with streamlined workflows. Perhaps as much a social phenomenon as a technical one?
Yeah it really was a social phenomena. Ten years ago conferences were swarmed with docker employees, swag, plenty of talks and excitement.
The effort to introduce the concepts to the mainstream can’t be understated. It seems mundane now but it took a lot of grassroots effort and marketing to hit that critical mass.