ClefOS is official

Or more precisely, ClefOS is an official image. Official image means, it is part of curated content on Docker Hub. It is also (AFAIK) the first official image that has no support yet for other platforms. Well, this might be a dubious comparison since it is actually an equivalent to CentOS which does not have any s390x backing. ClefOS can't be named CentOS, since Neale Ferguson and company at Sine Nomine Associates are not part of the CentOS organization. However, as you can see it is very closely following it:

$ docker run -ti clefos
Unable to find image 'clefos:latest' locally
latest: Pulling from library/clefos
26dbd8e1d5ff: Pull complete
Digest: sha256:8e89216b23e7a5716a7e31de352ed777769738d258a1e20cc9cff06e39316717
Status: Downloaded newer image for clefos:latest
bash-4.2# cat /etc/os-release
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"

bash-4.2#

This gives you a great option for enabling CentOS (or RHEL) based images on IBM Z. The identification above is technically very sane, since some projects check the distribution, and for some reason do not know ClefOS, but know CentOS.

An Overview on s390x Base Images

For s390x, quite a few options for base images are available on Docker Hub/Docker Store these days. They vary from enterprise environments over community distributions to minimal images. This post gives an overview on what is provided by various sources.

Another Base Image for Docker on z Systems: ClefOS

Neale Ferguson from Sine Nomine Associates has uploaded another base image: ClefOS. ClefOS is technically a CentOS port to z Systems, but since it is not a part of the CentOS organization, it's called ClefOS. The image is brunswickheads/clefos71-base-s390x (available tags listed here), so

docker pull brunswickheads/clefos71-base-s390x

will get you the image. It is yum-enabled, so you can easily install additional packages.

The user page https://hub.docker.com/u/brunswickheads/ provides a pile of nice images on top of ClefOS, so there is more software to play with... worth while checking out!

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.

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.

Creating Base Images

In First Steps with Docker, we have used a fairly crude way to create initial base images. A minimalistic approach to come to a base image environment is to have only the necessary rpms installed through on-board tools. This assumes the system is enabled for accessing all packages online.

Inspired from https://github.com/docker/docker/blob/master/contrib/mkimage-yum.sh, this script works both for SLES 12 and RHEL 7: