How does coreos compare to triton?

So in a way, this is an apples to oranges to grapes comparison. CoreOS is an operating system, Kubernetes is open source container orchestration software, and Triton is a PaaS.

So CoreOS, it's a minimal operating system with a focus on security. I've been using this in production for several months now at work, haven't found a reason to not like it yet. It does not have a package manager, but it comes preinstalled with both rkt and Docker. You can run both docker and rkt just fine on there. It also comes with Etcd, which is a distributed key-value store, and it happens that kubernetes is backed by it. It also comes with Flannel which is a networking program for networking between containers and machines in your cluster. CoreOS also ships with Fleet, which you can think of like a distributed version of systemd, which systemd is CoreOS' init system. And as of recently, CoreOS ships with Kubernetes itself.

Kubernetes is a container orchestration software that is made up of a few main components. There are masters, which use the APIServer, controller and scheduler to manage the cluster. And there are nodes which use the "kubelet" and kube-proxy". Through these components, Kubernetes schedules and manages where to run your containers on your cluster. As of v1.1 Kubernetes also can auto-scale your containers. I also have been using this in production as long as I have been using CoreOS, and the two go together very well.

Triton is Joyent's Paas for Docker. Think of it like Joyent's traditional service, but instead of BSD jails (similar concept to Linux containers) and at one point Solaris Zones (could be wrong on that one, that was just something I heard from word of mouth), you're using Docker containers. This does abstract away a lot of the work you'd have to do with setting up CoreOS and Kubernetes, that said there are services that'll do the same and use kubernetes under the hood. Now I haven't used Triton like I have used Kubernetes and CoreOS, but it definitely seems to be quite well engineered.

Ultimately, I'd say it's about your needs. Do you need flexibility and visibility, then something like CoreOS makes sense, particularly with Kubernetes. If you want that abstracted away and have these things handled for you, I'd say Triton makes sense.