http://en.wikipedia.org/wiki/Solaris_Containers

Of course, Solaris is even more despised by some people since they changed hands.

I think Docker appeals more to people, because:

- It's on Linux, which is more popular than FreeBSD or Solaris.

- It's very easy to set up and configure.

- Integration with Puppet et al.

- The have great marketing :).

Docker took a technology known to many that setup/admin/manage machines, added some fluff, made things simpler, and marketed the idea.

In a crowd that might spend more time thinking about nodejs and callbacks vs promises or how easily one can tip a rails app up on heroku, existing systems tools for things like jails/virtualization may either be over looked or not a concern.

For every docker, there are people (of which I may be one) that think , "big deal, it is just x". Meanwhile that thing is getting traction and popularity. It might not last, but it is around and making noise now.

Well what on earth do you need a pre-assembled computer for? You just take some circuit boards and a soldering iron, then assemble everything over the weekend and you have a perfectly good computer. I don't understand why this Apple I thing is so popular, it's nothing special.

Far as I can tell, every successful piece of tech out there can be reduced to "Added some fluff, simplicity, and marketing to an already existing technology"

(You could say same about Github, Travis etc.)

And I think that's the crux of it--do you think anyone would use Heroku if its container environment were FreeBSD-based? I'm guessing not; nobody develops on FreeBSD, so they'd have to test on a separate FreeBSD VM before deploying.

Containers aren't emulating anything or translating anything. They let your partition out system and network resources as you see fit (or to protect users from abusing each other) without running kernels within kernels and other performance killing hokum.

[1] dotCloud don't actually yet recommend running Docker in production, but if you did...

[2] This was part of what Mailgun (part of Rackspace) said in their presentation at the Docker workshop in SF today.

Standardization for the sake of standardization is not defensible.

Is there an explanation why 'in production' is actively discouraged? Is that a limitation of the underlying lxc stuff?

I ask, because the interesting parts of docker _for me_ seem to be focused on the setup, deployment - and not the runtime. So if I create a working image and want to use that in production, wouldn't docker become passive as soon as I run that thing?

What's the danger here?

As long as we're not comfortable operating Docker at large scale ourselves (we run quite a lot of containers in production at dotCloud), we won't recommend that others do it.

They belong to a category of virtualization known as 'container-based virtualization' which implements virtualized perspectives of the system within the host kernel, effectively dividing the system in to multiple systems (from the perspective of the affected processes). That is unquestionably virtualization.

I believe a statement closer to what you were looking to express was containers are not running under a hypervisor.

LXC still creates a performance impact, depending upon which options are selected, with particular note for the various memory accounting options. However, that impact is far lower than a hypervisor. In addition, startup times are vastly reduced since the kernel bootstrap and hardware detection concerns are rendered unnecessary.

Edit: I just realized that docker clusters is not being developed by the docker team

But then the "fix" is to have a farm of host machines of all supported configuration of kernel and architecture (mostly just Linux distributions). Migration and load balancing will be more rigid as can't move any machine to any host. Some hosts

What is not doable it seems is say supporting windows guests, older Linux kernels etc. That argues for a hybrid approach with a controller API on top that uses KVMs or Xen hypervisors alongside LXC

Also certifications. Government agencies for example will accept only certain OS-es have been certified. Sometimes it is simply because there are features on some distribution or kernels that aren't in others.

Docker is made to, basically, develop apps the same way you develop them when using a PaaS like Heroku (or, more specifically, a PaaS like Dotcloud): have a frozen base+runtime image; compose a "slug" consisting of exactly the stuff in your build/ directory and layer it on top; and tell the target host to launch it. To upgrade, create a new slug, and rolling-restart your old instances into new instances.

I haven't used Docker yet, I am only familiar with LXC so far so I was commenting on that. If one does have a uniform or a restricted set of platforms that can also act as LXC hosts then well why not take it and run with it. It is more efficient and that might translate into performance and cost savings.