An updated version of CentOS Atomic Host (tree version 7.20170428), is now available, featuring the option of substituting the host’s default docker 1.12 container engine with a more recent, docker 1.13-based version, provided via the docker-latest package.
CentOS Atomic Host is a lean operating system designed to run Docker containers, built from standard CentOS 7 RPMs, and tracking the component versions included in Red Hat Enterprise Linux Atomic Host.
CentOS Atomic Host is available as a VirtualBox or libvirt-formatted Vagrant box, or as an installable ISO, qcow2 or Amazon Machine image. These images are available for download at cloud.centos.org. The backing ostree repo is published to mirror.centos.org.
CentOS Atomic Host includes these core component versions:
The downstream release of CentOS Atomic Host ships without the kubernetes-master package built into the image. Instead, you can run the master kubernetes components (apiserver, scheduler, and controller-manager) in containers, managed via systemd, using the service files and instructions on the CentOS wiki. The containers referenced in these systemd service files are built in and hosted from the CentOS Community Container Pipeline, based on Dockerfiles from the CentOS-Dockerfiles repository.
These containers have been tested with the kubernetes ansible scripts provided in the upstream contrib repository, and they work as expected, provided you first copy the service files onto your master.
Alternatively, you can install the kubernetes-master components using rpm-ostree package layering using the command:
atomic host install kubernetes-master.
You can switch to the alternate docker version by running:
# systemctl disable docker --now
# systemctl enable docker-latest --now
# sed -i '/DOCKERBINARY/s/^#//g' /etc/sysconfig/docker
Because both docker services share the /run/docker directory, you cannot run both docker and docker-latest at the same time on the same system.
If you're running a previous version of CentOS Atomic Host, you can upgrade to the current image by running the following command:
$ sudo atomic host upgrade
CentOS-Atomic-Host-7-Vagrant-Libvirt.box and CentOS-Atomic-Host-7-Vagrant-Virtualbox.box are Vagrant boxes for Libvirt and Virtualbox providers.
The easiest way to consume these images is via the Atlas / Vagrant Cloud setup (see https://atlas.hashicorp.com/centos/boxes/atomic-host). For example, getting the VirtualBox instance up would involve running the following two commands on a machine with vagrant installed:
$ vagrant init centos/atomic-host && vagrant up --provider virtualbox
The installer ISO can be used via regular install methods (PXE, CD, USB image, etc.) and uses the Anaconda installer to deliver the CentOS Atomic Host. This image allows users to control the install using kickstarts and to define custom storage, networking and user accounts. This is the recommended option for getting CentOS Atomic Host onto bare metal machines, or for generating your own image sets for custom environments.
The CentOS-Atomic-Host-7-GenericCloud.qcow2 image is suitable for use in on-premise and local virtualized environments. We test this on OpenStack, AWS and local Libvirt installs. If your virtualization platform does not provide its own cloud-init metadata source, you can create your own NoCloud iso image.
Amazon Machine Images
The CentOS Atomic Host image follows the upstream Red Hat Enterprise Linux Atomic Host cadence. After sources are released, they're rebuilt and included in new images. After the images are tested by the SIG and deemed ready, we announce them.
CentOS Atomic Host is produced by the CentOS Atomic SIG, based on upstream work from Project Atomic. If you'd like to work on testing images, help with packaging, documentation -- join us!
The SIG meets weekly on Thursdays at 16:00 UTC in the #centos-devel channel, and you'll often find us in #atomic and/or #centos-devel if you have questions. You can also join the atomic-devel mailing list if you'd like to discuss the direction of Project Atomic, its components, or have other questions.
If you run into any problems with the images or components, feel free to ask on the centos-devel mailing list.
Have questions about using Atomic? See the atomic mailing list or find us in the #atomic channel on Freenode.