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Comment by moondev | Hacker News Reader

What is the motivation and benefit for running containers without docker?

Docker is by far the more mature and adopted development tool. It also runs great on windows, macos and linux.

While k8s can run containers via the rkt runtime, it's still pretty new and will probably introduce unnecessary headache and edge cases.

Docker also has a head start on a vibrant ecosystem for base images.

In my opinion it would be better to focus on docker, and when rkt gets there it shouldn't be much of an issue to switch if desired.

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Just to clarify two things:

- rkt can run any docker image in the vibrant ecosystem: https://coreos.com/rkt/docs/latest/running-docker-images.htm...

- Help test Kubernetes and rkt with minikube, it is working nicely today: https://github.com/kubernetes/minikube#using-rkt-container-e...

Good to know about rkt and docker images, I stand corrected. Looks like it supports remote docker registries as well.

Yes, it supports remote docker image registries and authentication to those registries.

> What is the motivation and benefit for running containers without docker?

I believe that Docker bet the company on the wrong business model. Therefore knowing that you can run containers without Docker can be desirable, as it gives you options in case Docker turns out to be not viable.

Docker made it easy to build and run containers from the command line. This technology was released at the right time and in the right place. And it got huge traction. Docker used this traction to get a very large amount of VC capital. Therefore they now need to show a very large return.

How do you go about achieving that large return? A common way to do this is to use one piece of technology that is popular as an anchor to lock customers into an entire stack. And then you monetize the stack, which is easier as it has higher value. The technology in this case is the container runtime, and the stack would be an full enterprise grade container orchestration system.

This strategy worked for others. Microsoft was a master in this. VMware as well, and so is Oracle. The reason I believe it will not work for Docker is:

1. The anchor technology is open source. Microsoft managed their lock-in via Windows, VMware via ESX, Oracle via their DB. It worked because those are proprietary. In the open source world you can just take Docker.

2. Even though the technology is open source, you can still try the ecosystem approach where you exploit certain network effects attached to your distribution of the code that protect you (e.g. vendor certifications). This is what worked for Red Hat. In my view it is unlikely to work for Docker. I don't think certifications are required as most container apps today are not vendor apps. And I would not know what else they could use.

3. For orchestration solution they are engineering against Google's Kubernetes. With all respect for Docker, this is going to be very hard as Google has a huge amount of experience in this area.

4. Due to Docker's need to protect their business model, there is no true community in the sense that there is an open exchange of ideas. The docker agenda prevails over technical decision making (like: should you have a docker daemon? Should Swarm be part of the Docker Engine?). Contrast that with Kubernetes which run in a very open manner by Google. This is why OpenStack got the traction, and why Eucalyptus and CloudStack died off. OpenStack had the most open community.

All of this can lead, IMHO, to a situation where Docker will not succeed in delivering Swarm as they see it. Kubernetes will become the default container orchestration system, and Docker is relegated to a small place in the stack. This situation would make it hard for Docker to justify their valuation.

> In my view it is unlikely to work for Docker.

Docker has realised the money is in the platform. So they're competing against Red Hat, who have OpenShift.

They're also my employers, Pivotal, and IBM, and HP, and SAP and every other company with a Cloud Foundry distribution.

The problem for Docker is that Red Hat, Pivotal et al started with selling an entire platform to F1000s. Docker and Kubernetes have great groundswell in the community, but the difference is that Docker need to make money from a sold platform and Google don't -- their play is GCP.

> For orchestration solution they are engineering against Google's Kubernetes.

Let's not forget Mesos, Nomad, Diego (the Cloud Foundry bits) and so on. And yes, it turns out this problem is actually very hard. Much harder than it looks.

> Due to Docker's need to protect their business model, there is no true community in the sense that there is an open exchange of ideas.

This is one of the reasons Pivotal donated Cloud Foundry IP to the Cloud Foundry Foundation, and it's why the Foundation rules are written to grant voting rights to members which contribute engineering effort. Red Hat are relevant as a large and critical part of an ecosystem. So it is for other successful OSS companies. But being the "owner" tends not to go as well. People who buy from us want to know that they can switch to IBM without much disruption and vice versa.

> This situation would make it hard for Docker to justify their valuation.

I can't blame them for trying. And I suppose they didn't see Kubernetes coming to suck the oxygen out of a big part of their platform.

The weird story of Docker will be of a company that created a PaaS, abandoned it for a component, then tried to build a PaaS.

Disclosure: as I noted above, I work for Pivotal. As Docker moves into platforms, we are competitors. Though we cooperate on runC.

Recently tried to run docker on Ubuntu Desktop 14.04. After googling a bunch of errors, trying different versions, but still failing decided to try rkt. That one worked out of the box, but apart from a bunch of simple images failed to run the caffe docker image.

So, my motivation of running without docker would be to understand every little thing they do to actually be able to use them and rely on them.

curl -sSL https://get.docker.com/ | sh

sudo usermod -aG docker $your_user

There ya go.

In newer distros its as easy as apt-get install docker.io

It installs fine, it just doesn't work. There is an issue on github with the same errors as I saw, where they discuss not fixing it, because of how uncommon the system is.

Can you link it here? I'm just curious. I run docker on trusty all the time

Me too. Never seen an error.

Adding a user to the dockergroup is a bad idea on a desktop.

Docker founder here.

> What is the motivation and benefit for running containers without docker?

I regularly hear from people who want to run containers without Docker. There are several motivations, all of which are perfectly valid:

1. Learning. It's fun to build things from scratch to understand how they work under the hood.

2. Bad experience. Early versions of Docker were quite buggy, and we initially struggled to keep up with the colossal growth in usage and feature requests. As a result, many of the people who tried Docker in production too early were badly disappointed. Some of them decided Docker wasn't for them, and started looking for alternatives.

3. Extremely custom use case. If your deployment is larger, or more complex, or more specialized than 99.99% of deployments out there, then "mainstream" platforms like Docker might not be the right fit for you. Of course we try to make Docker as customizable as possible, to support more a wider spectrum of use cases with plugins. But realistically, no single platform can cover all use cases, and I don't think any platform ever will. Docker is no exception.

4. Philosophy disagreement. Different people have different opinions on how applications should be developed and deployed. Docker tries very hard to be agnostic - to accommodate as many opinions as possible. But we can't please everybody. If Docker does not fit your philosophy of development and deployment, then the natural response is to look for an alternative.

5. Competition. Many Docker competitors started out as extensions or modifications of Docker, and over time are looking to reduce their dependency on Docker.

I'm probably missing other reasons, but these are the ones I've been most exposed to. These are all reasonable reasons to not want to use Docker.

Our approach is that, if you want to run containers without Docker, we should make it as easy as possible. In practice that means spinning out as many of the underlying components as possible (what we call the "plumbing") so that you can assemble it yourself without being stuck using the entire Docker platform. For example:

- containerd [https://github.com/docker/containerd] is our low-level container runtime.

- runc [https://runc.io] is a standardized "container executor", which we donated to the Linux Foundation as the reference foundation for the OCI spec.

- libnetwork [https://github.com/docker/libnetwork] is the low-level networking implementation (including overlay networking which is a very useful primitive for container clustering)

- swarmkit [https://github.com/docker/swarmkit] is a clustering/orchestration implementation

- notary [https://github.com/docker/notary] is a cryptographic content verification tool, which you can use to sign and verify container images.

- infrakit [https://github.com/docker/infrakit] automates the provisioning of infrastructure capable of running containers.

Our opinion is that, even if you don't use Docker, by using these components for your own purposes, you are indirectly contributing to making Docker better. Splitting out these components has also forced us to refactor Docker into a more modular, more robust design.

We even send Docker employees to explain how to run containers without Docker :) For example here's a talk we gave at Linuxcon: https://linuxconcontainerconeurope2016.sched.org/event/7oHM/...

You missed another, big reason: "Fewer, simpler moving parts" is the main reason I would prefer if Kubernetes could run without Docker as a container runtime.

At the moment, Kubelet needs to control the Docker daemon (a somewhat brittle relationship), and a bunch of concepts — from networking to volume management — could be simplified by making the container runtime more K8s-specific and less general-purpose. A tighter coupling would also mean you'd always be running K8s against the exact container logic it was made for, as opposed to now, where the loose coupling means you'll be subject to bugs (and there are so many) in new Docker versions.

That and the fact that Docker is increasingly building in competing concepts (services, etc.) via swarm mode, which I don't care for.

Docker still has a place for things like image building, of course.

I would categorize that under 5: competition. Kubernetes started out as an extension/modification of Docker, and over time Docker has evolved some of the same features as its kub-based competitors. The result is an uncomfortable integration between partially competing platforms.

Personally I think the long-term solution is for kubernetes to adopt containerd - it's the small, stable, rock-solid container runtime that it needs.

Whether the Kubernetes community continues to build primarily on Docker, or switches to containerd - either way we will support them and help in every way we can. Behind the superficial internet drama, there is a solid engineering collaboration between both communities, particularly between Docker and Google. We may disagree on a lot, but at the end of the day we have a lot of users who rely on us, and we have a responsibility to work together to solve their problems.

> Kubernetes started out as an extension/modification of Docker, and over time Docker has evolved some of the same features as its kub-based competitors. The result is an uncomfortable integration between partially competing platforms.

That's quite inaccurate. It's is like saying that OpenStack started out as an extension to KVM. Both had very different (original) scopes.

> Whether the Kubernetes community continues to build primarily on Docker, or switches to containerd

Kubernetes has 3 container runtimes at the moment: Docker, Rocket, and the new remote runtime which allows you to plug in a separate server using a protobuf interface. There is a lot of focus on the remote runtime now. The CRI-O project for example is implementing a remote runtime that allows any OCI conformant runtime to be plugged into Kubernetes.

All of the early Kubernetes resources I can find describe it as involving Docker. Was running it without Docker really a thing early on?

No. Kubernetes was launched at the first Dockercon, with a very specific focus of "we want to help expand what can be done with Docker by leveraging the significant operational experience we accumulated at Google". They delivered very successfully on that promise.

The focus on diversifying away from Docker is very recent, and is the direct result of the competitive tension I talk about earlier in the thread. It's completely understandable.

EDIT: A perfect example of that competitive dynamic is actually this very thread! the GP (`sysexit`) works at a competing vendor. You can tell in his post that de-emphasizing the dependency on Docker is important to him. In fact that talking point is so recognizable that I knew where he worked before even looking him up. There is nothing wrong with that, every vendor has an "official party line", and Docker is no exception. The point is, this is a delicate issue which has more to do with inter-personal and business dynamics than with code. And you should definitely verify the credentials and agenda of everyone speaking of authority on the topic of containers platforms. We vendors are everywhere, and we are biased as hell.

> The focus on diversifying away from Docker is very recent, > and is the direct result of the competitive tension

I think you miss a reason at least equally as important, if not more: There are a lot of people who want to do non-container runtimes but still leverage the rest of Kubernetes. I don't want to say no to them (who am I to decide what tech is "good"?) but I don't want their code in my tree (too big already, too hard to maintain, too much email, etc).

Ergo: plugins.

You're absolutely right. I was focused on the subset of kub-based platforms which are container-focused and are overlapping more and more with Docker.

But you're right, kub itself is a neatly generic orchestration component which can be used with non-container things. That is an excellent reason for decoupling the underlying container runtime.

> We vendors are everywhere, and we are biased as hell.

As a Pivot, I can confirm: I am biased as hell.

My day job is not related to containers, but yes, working in the industry has of course biased me (but my opinions are still my own).

Docker have broken out some Docker logic into libraries, which is why the Garden team swapped out their driver to use runC. Kubernetes could presumably follow suit and target the libraries instead of the Docker daemon.

The experience of the Garden API (a containerising system that ultimately predates Docker) is that tighter coupling is actually a mistake.

If Garden had been tightly bound to its implementation or orchestrator, it'd still be using raw Linux system calls and running under a 2nd-generation orchestrator.

Instead it's now using runC, OS X or Windows APIs to create containers and runs under multiple consumers -- most heavily under Diego, a 3rd-generation orchestrator and Concourse, a project automation tool.

Disclosure: I work for Pivotal. Many, but not all, of the engineers who've worked on Garden work for Pivotal also.

My main concern is coming across a an issue only to research it and find a "won't fix"[closed] and 100 +1s asking for it. When I have something super important in actual production this scares me way too much to trust.

1000x this. Pretty much sums up my experience with Docker so far.

Great concept, poor execution.

That's where the competition will come in handy. Docker Inc has its own corporate goals. Luckily, they are decoupling the underlying components more and more.

Just curious: Which issue(s) are you talking about?

One that comes to mind is folks asking for relative path support in Dockerfiles (though I understand why the Docker folks don't want to do that).

I can't comment much on docker as I have little experience but can I say this is a really honest and courageous post - I would have expected some corporate-speak not "we got things wrong early on", and a self-awareness and openness about the challenges being faced at a corporate level that has made me change my mind about the amount of trust to put in Docker the company.

Mad props.

Docker founder here.

Great! There is one question I would like to have answered, by you and you alone:

if I'm using SmartOS, and therefore zones, and all my applications and configurations are packaged into OS packages, and I use imgadm(1M), vmadm(1M), and Smart DataCenter (SDC), what do I need Docker for?

Nothing. You've already spent all the time and effort that Docker would save you. Have fun maintaining OS packages.

As I wrote previously, the question is for the founder of Docker and him alone, but since you volunteered your opinion, I am extremely pleased to inform you that I love making OS packages and performing configuration management at scale that way. I especially enjoy being able to ask the operating system's software management subsystem exactly which configuration changes have been done to it, and get a precise response back. I enjoy it even more when I am able to perform mass in-place upgrades of configuration, on tens of thousands of systems, in parallel, because I'm performing configuration management using operating system packages, or simply destroy the system's boot block, reboot it, and have the network instantiate it, from bare metal to fully configured virtual servers ready to serve data, by just using Kickstart, JumpStart(TM), or SDC, without any additional code. No Chef. No Puppet. No cfxengine. No Salt. No Ansible. No Docker. No KVM. No XEN. No Kubernetes. No Mesos. No extra software or daemons required or needed, other than what ships with the OS.

Fully isolated, virtualized UNIX servers. Servers are cattle, not pets. Deployments in up to 25 seconds.

That was the challenge. And it was fun to solve.

Have fun maintaining OS packages.

Oh I am! It's incredibly satisfying to be able to run systems where no human has ever logged into, and no file has ever been manually modified, and all the files and all the changes are accounted for by the operating system.

See also, not quite the same, but very much related and relevant to your comment:

http://www.perkin.org.uk/posts/building-packages-at-scale.ht...

https://blog.nimbleci.com/2016/10/11/how-to-deploy-jenkins-c...

https://news.ycombinator.com/item?id=12750685

Configuration management at scale, using an operating system's software management subsystem is the old, new-new thing. It is the foundation and the future of even more massive cloud computing. Now you'll be able to say someday in the future: "ha! I read that on Hacker News years ago!", and point to this post.

> by just using Kickstart, JumpStart(TM), or SDC, without any additional code. No Chef. No Puppet. No cfxengine. No Salt. No Ansible. No Docker. No KVM. No XEN. No Kubernetes. No Mesos.

Thank you for saying this! Building OS packages and OS images and provisioning servers was done automatically 10 to 12 years ago with much less work.

It's still the preferred choice for many large tech companies and nobody talks about it because it just works and it's nothing new. Fast deployments, immutable infrastructure, modularity.

Much less work than what?

Much less work than messing with Docker, Mesos, Kubernetes, Chef, Puppet, Rkt, Salt, Ansible, cfengine, etcetera... it's much, much simpler to build OS packages and keep the metadata needed to build them under revision control (git, Mercurial, Bitkeeper, ...) And as a bonus, it is designed to plug into the change management process from the ground up, and not as an afterthought. (Deployment automation and configuration management are not enough for complete lifecycle management.)

So what are you bugging shykes for? You have achieved everything Docker offers, and you had fun in the process. Seems like you're smart enough to realize that.

Anyway, someday in the future I might look back on this and think "ha! someone put all that effort in even though NixOS already existed".

So what are you bugging shykes for?

All I did was ask a question.

Is critical thinking, even just asking questions, undesirable now, unless someone is being praised to high heavens? Is that what we're down to now?

"ha! someone put all that effort in even though NixOS already existed"

SmartOS virtualization is based on Solaris zones, which existed long before people on GNU/Linux even realized that containers were the way to go. The groundwork, and my own work was laid down long before any of this became hype. Project Kevlar, nee zones was started around the same time as NixOS, and another participant already mentioned that large companies did large scale deployments and configuration management via OS packages, which is both true and correct.

You did not just ask a question as a form of critical thinking. You asked a question leading into a lecture on the technology you prefer.

Docker is just a simple wrapper that reduces the amount of knowledge needed to run a containerized process. It did not become hype because of any technological advantage, it became hype because this old technology became accessible not just for the kind of people/companies that don't (can't) run enterprise class Solaris deployments, but also the kind that don't have 20 years of experience in making robust well managed deployments.

Your process might seem easy and straightforward to you. But for the average developer and Linux enthousiast, there's not much that can the simplicity of the Dockerfile. Systemd or a more specialized system like Kubernetes to run the containers, and a simple script to provision your machine is all you need. You can pick all of this tech up in a few days and steadily grow into more advanced subjects like monitoring, logging, security.

Anyway, you're not helping anyone by just saying "SmartOS is better than Docker+(list of redundant and unrelated other tech)", maybe instead show us a one-page tutorial on how to set up a SmartOS system with a webapp stack (i.e. LAMP, MEAN or RoR) that can be executed by a newbie without a creditcard, registration, trial or phone call.

You did not just ask a question as a form of critical thinking.

Yes I did.

You asked a question leading into a lecture on the technology you prefer.

Only after you left your Good luck with packaging everything, which I have good reason to believe was cynical sarcasm.

It did not become hype because of any technological advantage, it became hype because this old technology became accessible not just for the kind of people/companies that don't (can't) run enterprise class Solaris deployments,

Performing configuration management at scale with OS packaging has nothing to do with Solaris - it works on any operating system which has a Bourne-family shell, AWK, and sed.

but also the kind that don't have 20 years of experience in making robust well managed deployments.

Then it would be a good idea for such people to actively seek mentors.

But for the average developer and Linux enthousiast, there's not much that can the simplicity of the Dockerfile.

That's what distinguishes the average developer. A true enthusiast will go out of their way to become a master of the art, so the assertion doesn't apply to them.

It's easy to hack several hundred thousand files together and deliver them via Docker. But, what happens when it's time for upgrades? Go through the entire hackfest again? Every time?

Anyway, you're not helping anyone

that depends on what your mentality is: if you're a true enthusiast, you're probably reading a lot, and when you stumble upon crumb trails like mine, the light bulb might go off reading what I wrote, and it might just be the clue you need (that's the idea). And you wouldn't be the first or the last person that happened to.

As for me, I'd gladly show how to do what interests you, only I have no blog, and no time to set one up, fight spam, hack attempts, and so on. I can afford one short answer like this, but I cannot afford months of engineering implementing the infrastructure for a blog and hardening it.

And by the way, nice stab at Joyent on your part, but SmartOS is free, open source software, and the entire ecosystem + the 14,000 packages never cost a penny. Even their cloud on a laptop ("COAL") preconfigured image is gratis.

As for packaging being hard... there is such an abundance of packaging documentation for any popular operating system... all you have to do is sit down and "warm up the chair" by reading it. Do you think I learned it some other way?

    which I have good reason to believe was cynical sarcasm.

Well true, and I apologize. I have done some packaging for Debian, CentOS and recently Alpine and whilst the systems are smartly designed and effective, using them is neither easy nor enjoyable. Their complexity stems from the fact that they're smart and strict about dependencies. Docker sidesteps this by making images entirely self contained. This might not be your cup of tea, obviously it wastes system resources, but it does simplify the ordeal.

    Then it would be a good idea for such people to actively seek mentors.

Or they could use Docker and focus their energy on building value for their company so at some point it can afford to employ proper system administrators. Who then may or may not decide to migrate the systems to SmartOS.

    Do you think I learned it some other way?

I don't and neither did I. I just think that if knowledge-intensive engineering can be avoided it is worthwhile. Especially when an operation is young.

Well true, and I apologize.

Gladly accepted.

I have done some packaging for Debian, CentOS and recently Alpine and whilst the systems are smartly designed and effective, using them is neither easy nor enjoyable.

I cannot write anything of Alpine Linux, as I have never used it, but I have done Debian / Ubuntu packaging and configuration management with packages, and that, compared to RHEL / SLES / SmartOS / Solaris / HP-UX / IRIX, was the hardest to get right.

One of the reasons why Debian and Ubuntu are so hard to get right is that the Debian packaging guidelines are insane: for example, it is not allowed to have packages named in any way other than lowercase; there is no /opt, as the Debian people do not understand the filesystem hierarchy standard and consider it a hindrance, for reasons completely unknown to me.

So now imagine you had to build, say, your own PHP with OCI8 support: you cannot name the package php, nor can you deliver it into /usr, because the next upgrade from Debian could break your production. And there is no /opt, so neither vendors nor other 3rd parties have a place to safely deliver their software (/usr/local is not it, and is against standards).

What I'm trying to say is, you picked one of the worst operating systems, ever. Even RHEL, as bad as it is, is nowhere nearly as poorly designed as Debian GNU/Linux.

Pick a better OS. pkgsrc format is pretty straightforward, and AT&T SVR4 packaging[1] is the absolute best when it comes to doing configuration management. Unbeatable.

This might not be your cup of tea, obviously it wastes system resources, but it does simplify the ordeal.

If delivering software which JustWorks(SM) is an ordeal, then you need to step back and seriously re-think what needs to be corrected. Delivering software should be a breeze, and it should happen automatically, meaning that the software management subsystem of the OS should worry about it for you. But that also requires you to seriously revise how you put software together, because if it's an ordeal for you, something is majorly wrong. (Since I don't know your situation, I cannot comment what.)

This line of thinking, is, in my experience, completely, utterly incorrect on several levels:

developers should not act as if system administration is beneath them. One can never, ever become a master developer without becoming a top-notch system administrator: how can anyone develop software which is correctly integrated and runs on an operating system, if they do not understand how to administer that system? I have seen that over and over and over again in my decades of experience, and I have seen no developer who was able to code quality software which the system administrators didn't hate, because it was all hacked up and required lots of hacking to get working.

I just think that if knowledge-intensive engineering can be avoided it is worthwhile. Especially when an operation is young.

If you do that, it will come back to haunt you. With a vengeance. And the reason it will come back to haunt the company is because it's taking on a huge technical debt.

Are you familiar with the concept of taking on technical debt?

[1] http://heirloom.sourceforge.net/

Containers existed before Docker and will exist after Docker, and articles like these are desperate attempts to remind everyone of that in the face of Docker's unilateral destruction of the concept. I know I'm right because of comments like these that presuppose "well, if you're doing containers, use Docker, the alternatives just aren't there." Except they were, before Docker, and after Docker.

Docker is a developer tool, not a container runtime. The 'containers' it presents require you to commit a daemon on every machine, commit to a weird storage and distribution story when, you know, files of containers served in a flat directory are totally adequate, and so on. Docker made extremely complicated choices for a lot of things and now everybody wishing to advance containers has to deal with presuppositions like these, where Docker exists and the motivation for not using it is unclear to a lot of people, you included.

Docker is a container runtime, not merely a developer tool. It was intended as such from the beginning. It is successfully used in production at large scale by a number of companies, including Uber.

The fact that you don't like Docker doesn't change any of that. If you don't like it, don't use it. But there is no justification for you to claim it is only a developer tool when it is obviously more than that.

Docker was originally built on top of LXC. It is now becoming more flexible with what is underneath, but there's a reason you need a VM running in the background on macOS to use Docker.

Docker is tool to interact with LXC (and hopefully other container systems).

Docker doesn't use LXC anymore[1]. The reason you need a VM is to get the Linux kernel, not LXC, and the reason you need that is because the macOS kernel (Darwin) doesn't have the necessary containerization features. On FreeBSD, for example, Docker runs natively, without a VM.

[1] https://www.infoq.com/news/2014/03/docker_0_9

If MacOS doesn't have certain linux kernel features, neither does FreeBSD. How can Docker run on FreeBSD when FreeBSD has no cgroups? I think you misread/misinterpreted your reference.

> How can Docker run on FreeBSD when FreeBSD has no cgroups? I think you misread/misinterpreted your reference.

FreeBSD can run 64 bit and 32 bit Linux binaries via it's Linux emulator[1]. Plus FreeBSD has had containers since FreeBSD 4 which was released in March of 2000, except containers on FreeBSD are called jails.

> If MacOS doesn't have certain linux kernel features, neither does FreeBSD.

Just because one operating system doesn't have a feature that does not mean a different operating system does not have that feature.

[1] https://www.freebsd.org/doc/handbook/linuxemu.html

Jails are considerably different than containers. Jails are more like chroot jails on linux instead.

Edit: My viewpoint was focused more on the composability aspect of containers. But I stand corrected otherwise.

> Jails are considerably different than containers. Jails are more like chroot jails on linux instead.

Thats incorrect both jails and "containers" are examples of OS level virtualization[1]. Instead of virtualizing the hardware you virtualize the operating system, ie system call table.

[1]: https://en.wikipedia.org/wiki/Operating-system-level_virtual...

No, jails are basically containers. Docker on FreeBSD uses jails for isolation -- see the wiki page at https://wiki.freebsd.org/Docker

xhyve and bhyve virtualization built into the BSD kernels. docker for mac now runs a tiny linux vm directly on osx

So what is your alternative? Run containers your own unique way and roll your own distribution mechanism and networking to fragment yourself from the tools in the "container" space?

When "your own unique way" requires less development time and efforts and it's easier to learn for new hires, yes. That's why you hire system engineers - to write good automation.

The motivation is to make a smaller change to their operations and infrastructure. Right now they are running application services on linux machines using puppet to make the machine environment work. Switching to a container gives them reproducible environments that work on a developer workstation and a server. It also gives some operational benefits for how you run a process I think. You can do this without buying into the docker daemon, network overlay, orchestration. If you are currently able to deploy services on linux to production then you can do that, but with containers. This is an incremental win.

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