Docker and z/VM or KVM?

At LinuxCon, KVM for z has been announced. From a Docker perspective, what does KVM change over a z/VM environment? There's a pretty short answer: nothing. KVM is cool for a number of things, z/VM is still king of the road, PR/SM still has got some bragging rights, and Docker doesn't care, as long as a Linux runs in it. Docker under both z/VM and KVM benefits from complementing technologies.

Closing Another Base Image Gap

Most recently, I mentioned (here and here) how to best deal with the fact that Ubuntu is widely used as base image, but does not exist on z Systems. A sufficiently close Debian is a decent solution for that.

Today's announcement at LinuxCon shows how this will get even easier: Ubuntu will be made available on z Systems. This will make all "FROM ubuntu" images no-brainers.

Image Decomposition

Looking at the swarm image we built previously, it's a couple of hundred MB in size -- for a small application. This image size will not slow down execution, since only files are touched which are needed when the application starts, but it will still be offending an aesthete's eye. Specifically for mainframers who have tried to save on every bit, because their core memory only had a couple of them (my knowledge is entirely anecdotal...). How can we kill that pain?

Portability Series: A Go Environment

Previously we looked at the portability of container setups. One of the observations is that a lot of containers are based on a Go environment -- take swarm or the registry. On x86, that usually means golang, but we have gccgo on s390. Let's see, how we can deal with this difference.

Portability Series: Usage of a Debian Base Image: compose

So we have created a Debian base image and are looking at some of the steps to run containers which may have platform dependencies. An example which brings this together is one of the Docker ecosystem components: compose. Docker compose lets you define applications which consist of several containers. You can the manage your entire multi-container application with single commands.
Let's get the code for compose:

Portability Series: Another Base Image

In the previous post, we looked at various challenges when moving existing (read: x86) container setups onto z Systems. One challenge is the widespread use of Ubuntu as Docker base images. The closest thing on z is Debian having roughly the same packaging structure and naming.

Let's have a look how we can easily get to such an environment.

A Look at Docker and Portability

Often enough, Docker is mentioned in one breath with portability. However, there are two dimensions of portability: first, running a container on any system of the same platform. Here, Docker really simplifies deploying applications on any system (of the same instruction set architecture). From a Linux on z Systems perspective, the second aspect of cross platform portability is more interesting: portability across platforms. Often enough, getting a container to run on z is not a big deal, but sometimes it is. Let's decompose this: