Execute Docker Containers as QEMU MicroVMs
mergeboard.com
mergeboard.com
The project later merged with Intel Clear Container to become what's now called Kata Containers (https://katacontainers.io/) and is now widely used by several Internet giants like Alibaba and Baidu.
The startup was acquired by Ant Finance a couple of years ago.
(I recorded a podcast with one of hyper.sh engineer if you can listen to Mandarin https://pan.icu/25)
It actually worked great, and I've struggled to get as quite a flexible CI system at other jobs since then (the big advantage was it looked like Docker, so with compose you could either spin a metal-like nested VM or just pull in some DB containers in your build instance).
Still, neat to have the walkthrough here in this post.
https://www.linux-kvm.org/images/d/d2/03x05B-Chao_Peng-Light...
The big win was slashing away the BIOS stuff.
We use AWS's Firecracker to turn our customers Docker containers into Firecracker microvms (Firecracker is Amazon's Rust VMM, the engine for Fargate and Lambda). Anecdotally: in my dev environment, the difference between Firecracker boot times and native Docker container startup is imperceptible; the logging we do swamps the VM boot stuff. It's very fast.
Shameless plug: this is exactly what our goal is with https://kwarantine.xyz We are creating a new hypervisor (from scratch) that can run strongly isolated Docker/LXC containers.
Minor quip though since ptrace might even be slower than vm exits; your core point stands.
$(MAKE) -C linux-$(KERNEL_VERSION) ARCH=um linux
This is a rather old version -- newer versions check the checksum and use my HashCache system.
[1] https://cappsule.github.io/ [2] https://en.wikipedia.org/wiki/Bromium#/media/File:Bromium-en...
It's powered by https://github.com/containers/libkrun.
1: https://thekev.in/blog/2019-08-05-dockerfile-bootable-vm/ind...
Seriously, VMs are hardly as secure as many people want to believe unless you're utilizing enclaves and even that has vulnerabilities. I think a better approach is Seccomp and whatever other filtering makes sense.
gVisor is a very cool codebase. As an illustration of the approach: it includes its own TCP/IP stack; we use it in our command-line dev tool to allow people to SSH to their VMs over WireGuard without having to install WireGuard or obtain privileges to manage WireGuard.
I came away baffled that they weren't more widely-promoted, compared with Docker and friends. After thinking about it for a while, all I can figure is they're so straightforward to use and well-documented that there's no room to make one's name, or to make a buck, re-packaging them or wrapping them in complex tools, so there's little money or glory (= personal marketing via open-source project leadership/contributions) in promoting them.
[EDIT] that is: what would be a blog post in LXC/Docker land... doesn't exist, because it's covered perfectly well in the docs. What would be a simple open-source tool... becomes a blog post, because it's short, simple, and clear enough not to merit special software, but just a quick guide to existing tools. What would be a business, becomes a simple open-source tool without enough of a difficulty/convenience "moat" to support a business.
As a developer, how do I run FreeBSD Jails on my MacBook during development? With Docker for Mac, it is trivial for me to do everything on my Mac, and the fact that there is a virtual machine is completely invisible to me. Everything "Just Works". With FreeBSD Jails, I would have to actually interact with a VM constantly, including the pain of shipping files back and forth.
As a developer, are popular databases and applications pre-packaged as FreeBSD Jails so that I can spin one up on my laptop with a single command? Where is the Docker Hub equivalent?
As a developer, how do I orchestrate a collection of FreeBSD Jails for each project? With Docker, I define a single `docker-compose.yml` file for each project. With a single `docker-compose up`, the entire project is running including dependencies such as databases and other related projects in a completely reproducible fashion. This makes it trivial for coworkers to spin up a project on their machine and immediately be productive without spending an hour trying to get all the right versions of everything installed and up and running.
As someone responsible for deploying an application to production, what is the story around FreeBSD Jails for deploying across a cluster? Is there a Kubernetes-equivalent that can manage the allocation of resources, blue-green deployments, and manage the lifecycle of my FreeBSD Jails?
As someone responsible for deploying an application to production, do any of the major clouds support FreeBSD Jails? With Docker images, I can deploy those straight to ECS Fargate, Google Cloud Run, and half a dozen other services. Then I don't even have to think about my own infrastructure unless I need some really specialized hardware for a specific application.
> the rest barely matters anymore.
Everything else matters so much.
As to your earlier point about ZFS, most Linux distros these days seem to trivially support ZFS. Even TrueNAS is working on switching to Linux with their TrueNAS Scale offering.
It's not that I'm opposed to FreeBSD... FreeBSD is just a hard sell. It's hard to pin down exactly what you're gaining by throwing out all the collective Linux knowledge of an organization and switching to FreeBSD. FreeBSD is an N-th tier platform for pretty much every programming language except C, so good luck when you run into random subtle problems. Also, good luck doing hardware accelerated machine learning inference or training on FreeBSD... it's probably possible?
> the single important binary
This is also such a weird thing to throw out there. I like a good Go program myself, but most companies are not only deploying single-binary statically linked applications. Most companies are also deploying some kind of Ruby, Python, or Java application... none of which are likely to be a single file in practice. Most of them will have a variety of shared libraries, and I don't know if I've ever seen a Ruby application shipped in a `FROM scratch` container before. Technically possible, but that's just not common reality as far as I've seen. It sounds like you're proposing that everyone is already running in `FROM scratch` containers, so a FreeBSD Jail is just a drop-in replacement.
Linux containers are far from perfect, but as a developer... I have played with FreeBSD Jails before, and come away frustrated by all the work you have to do yourself.
The closest you can get is BastilleBSD (framework for FreeBSD Jails) and their templates - available here:
https://github.com/BastilleBSD/templates https://bastillebsd.org/templates/
> This is also such a weird thing to throw out there. I like a good Go program myself, but most companies are not only deploying single-binary statically linked applications. Most companies are also deploying some kind of Ruby, Python, or Java application... none of which are likely to be a single file in practice.
Sure, but usual practice with containers is to put each thing in its own, unless they are very tightly coupled. Web-app with a SQL database and a memory cache? Three containers. You can do otherwise, but that's typical. Usually each container ends up with one main, important running process, and not much else.
[EDIT]
> As someone responsible for deploying an application to production, what is the story around FreeBSD Jails for deploying across a cluster? Is there a Kubernetes-equivalent that can manage the allocation of resources, blue-green deployments, and manage the lifecycle of my FreeBSD Jails?
> As someone responsible for deploying an application to production, do any of the major clouds support FreeBSD Jails? With Docker images, I can deploy those straight to ECS Fargate, Google Cloud Run, and half a dozen other services. Then I don't even have to think about my own infrastructure unless I need some really specialized hardware for a specific application.
These are exactly the kinds of things I was thinking of when I noted that the OS itself has been seriously diminished in importance, for modern workflows. I agree that most commercial or high-profile open-source "cloud" tools and platforms are built around LXC/Docker.
I agree, but... getting all the application dependencies in there is more than just getting a single binary in there. If it's just a single-binary Go program, then a Jail works just fine, but it's not that simple for a Ruby application. I'm definitely not talking about databases running in the same container as the application. That's where Kubernetes and docker-compose come in for multi-container orchestration, which are things that FreeBSD Jails don't have as far as I know.
> These are exactly the kinds of things I was thinking of when I noted that the OS itself has been seriously diminished in importance
Yes, but... these are all the things that FreeBSD doesn't offer. These are the real reasons that people don't talk about FreeBSD Jails in the same breath as Docker. The Docker container itself (or the FreeBSD Jail) as a unit of isolation is the least interesting part of the ecosystem. All of the developer tools, orchestration tools, and prebuilt images are what make the Docker universe so interesting, and make FreeBSD Jails... less interesting.
You said you were confused why Jails don't have more mindshare. It has absolutely nothing to do with people being able to invent useless tools and write blog posts about them, and it has absolutely nothing to do with FreeBSD Jails being too well documented. You kind of implied those were the best explanations you could come up with. Those are not the problems at all, and it seems disingenuous to me to say you think those are the problems unless you really didn't know the things I mentioned in my first reply.
500-line config, much of which few people ever care about, with all kinds of ill-conceived nesting? Better put the ~20 options that 99% of users ever touch in environment variables, and document them. Weird state garbage that's not captured in your config-on-disk? Better figure it out and get it into env vars, and have your startup script use those to transparently manage whatever bad decisions you made re: state in the past. Shit files all over the system? Better get that sorted out so people can handle persistence with at the very most three total mounts—and oh, gee, look, now your simple example docker-compose also serves to document where exactly you store files. And so on.
(my second-favorite thing is that it's a de-facto cross-distro package manager with very up-to-date packages that are trivial to completely and cleanly uninstall)
I used my first Jail in 2001.
Docker was started over a decade later in 2013.
It’s reasonable to be confused why Jails lacks the mindshare. “Because it lacks all these other over-the-top features that we need” might be reasonable in response, except that Docker didn’t have any of these things on day 0 either.
Jails had a 14 year head start, Docker reinvents the wheel, and nor particularly well at first. Why did it succeed more than Jails did? It wasn’t because of the piss-poor native Mac support.
Jails seem to be treated like OpenVZ containers in the Linux world: a lighter alternative to virtual machines, not a way to build and distribute applications like Docker.
This is just my take after playing a few hours with jails, I would happily be proven wrong.
Security and performance aren't the only driving forces; there are a lot of technical and operational benefits to the abstraction and standard interfaces that you get when running stacks that might otherwise look like someone took an Xzibit meme too far.
Also remember on a modern system, there are often at least 2 additional layers at work abstracting interfaces to the "bare metal" OS already.
But the attack surface of a Linux kernel is very large, is pretty unpredictable, and can't be coherently masked out with rules (my favorite example Jann Horn's VM reference count bug, which was a simple concurrency flaw in the core virtual memory system). By comparison, a Linux KVM hypervisor is not just a subset of the kernel by definition, but also a much smaller codebase, a tiny fraction of the whole kernel.
Replacing shared-kernel isolation like seccomp-filtered containers with VMs is, architecturally, simply the replacement of a large trusted computing base with a smaller one. If the overhead is acceptable, it's hard to argue with from a security perspective.