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:

• atomic-1.15.4-2.el7.x86_64
• cloud-init-0.7.5-10.el7.centos.1.x86_64
• docker-1.12.6-16.el7.centos.x86_64
• etcd-3.1.3-1.el7.x86_64
• flannel-0.7.0-1.el7.x86_64
• kernel-3.10.0-514.16.1.el7.x86_64
• kubernetes-node-1.5.2-0.5.gita552679.el7.x86_64
• ostree-2017.3-2.el7.x86_64
• rpm-ostree-client-2017.3-1.atomic.el7.x86_64

Containerized kubernetes-master

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.

docker-latest

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.

Upgrading

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

Images

Vagrant

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 

ISO

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.

QCOW2

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

Region	Image ID
ap-south-1	ami-9c7b06f3
eu-west-2	ami-14425570
eu-west-1	ami-a1b9b7c7
ap-northeast-2	ami-e01cc18e
ap-northeast-1	ami-2a0d304d
sa-east-1	ami-ce7619a2
ca-central-1	ami-8b813def
ap-southeast-1	ami-61e36702
ap-southeast-2	ami-84c7cde7
eu-central-1	ami-f970ae96
us-east-1	ami-4a70015c
us-east-2	ami-d2cfe8b7
us-west-1	ami-57ba9c37
us-west-2	ami-fbd8bd9b

SHA Sums

977c9b6e70dd0170fc092520f01be26c4d256ffe5340928d79c762850e5cedd9  CentOS-Atomic-Host-7.1704-GenericCloud.qcow2
781074c43aa6a6f3cad61a77108541976776eb3cb6fe30f54ca746a8314b5f87  CentOS-Atomic-Host-7.1704-GenericCloud.qcow2.gz
aef7fedf01b920ee75449467eb93724405cb22d861311fbc42406a7bd4dbfee2  CentOS-Atomic-Host-7.1704-GenericCloud.qcow2.xz
669c5fd1b97bc2849a7e3dbec325207d98e834ce71e17e0921b583820d91f4f5  CentOS-Atomic-Host-7.1704-Installer.iso
b5ef69bff65ab595992649f62c8fc67c61faa59ba7f4ff0cb455a9196e450ae2  CentOS-Atomic-Host-7.1704-Vagrant-Libvirt.box
73757f50ef9cdac2e3ba6d88a216cca23000a32fa96891902feaa86d49147e3f  CentOS-Atomic-Host-7.1704-Vagrant-VirtualBox.box

Release Cycle

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.

Getting Involved

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.

Getting Help

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.