Alternatives to Docker: LXD and Rocket

Two recently announced alternatives to the Docker Linux container runtime LXD and Rocket aim to offer some interesting value propositions. Before I get to the details, let's first identify what use cases and aspects of the Docker container runtime of interest here. Docker identifies a few major categories of use cases: continuous integration, continuous delivery, scaling distributed applications, and Platform-as-a-Service. The former two are DevOps use cases. At this point, Docker pretty much has a lock on DevOps use cases. Moreover, neither of the would-be competitors truly target DevOps. It becomes obvious when you consider that LXD was intended to run on OpenStack Server environments and Rocket on CoreOS/fleet (though it is not necessarily tied to CoreOS). Docker runs on workstation environments and even on top of VirtualBox via boot2docker to support DevOps functionality on MacOS X. The more competitive aspect is the cloud infrastructure one. Here, Docker is competing with a wider range of technologies to support scaling on the cloud and providing PaaS functionality. This is the market where LXD and Rocket would operate. This is also the area where hypervisors have reigned.

Container Virtualization Options

photo by sioda	via PhotoRee

Looks like the container virtualization space is becoming a little more interesting this week. Previously, Docker was the only more or complete standard container implementation (with definition of image, image creation, and container start/stop management). There was Canonical's LXD, it didn't seem to be garnering nearly as much attention and support since it was only announced a month ago. However, with the Docker and CoreOS organizations starting to encroach on each other's territory, the CoreOS community has released an early version of their own container runtime, Rocket. On the balance, Docker has moved into the container cluster orchestration and management space with Docker Swarm and Docker Compose, the latter being still in the design stage.