Definition

Red Hat Atomic Host

Contributor(s): Jack Wallen

Red Hat Atomic Host is a variant of the Red Hat Enterprise Linux supported, open source operating system, designed to be a minimal OS with optimizations for container hosting. Its full name is Red Hat Enterprise Linux Atomic Host, but the product is commonly referred to as Red Hat Atomic or Atomic Host or by the acronym RHAH.

Project Atomic is an upstream collection of open source container OS technologies, which includes Atomic Host. This upstream Atomic Host works on Red Hat as well as Fedora and CentOS Linux OSes. Red Hat is an established Linux OS vendor, with long-standing relationships with enterprise customers. Red Hat Atomic Host is available for Red Hat Enterprise Linux (RHEL) subscribers and the versions are kept in sync. Additionally, Red Hat OpenShift users are advised to pair their version of OpenShift with the matching version of RHAH to enable maximum compatibility and automation under the covers.

The Project Atomic take on a container hosting OS is designed for large-scale workloads, a large number of basically identical distributed machines. Red Hat Atomic Host embeds Docker, atomic, etcd, flannel and other container operations tools into the operating system. Libraries and packages unnecessary for container operations are not included in the OS, which keeps it lightweight and efficient.

Deploy Red Hat Atomic Host

Red Hat Atomic Host can be deployed on physical hardware, certified hypervisors such as Red Hat Enterprise Virtualization and VMware vSphere, and private or public cloud infrastructure such as Amazon Web Services and Google Compute Platform. It includes a read-only file system, fewer packages than the general purpose RHEL set, and a single command -- atomic -- to manage host changes. Red Hat Atomic Host systems are designed for ephemeral and highly automated deployments unlike RHEL; individual host customization and control is limited.

Updates to the Red Hat Atomic Host OS can be downloaded and deployed in one step via the atomic management command, which encourages simple update and rollback of changes. When an image is updated, the previous version is retained for rollback, but there is no mixing of two versions.

Project Atomic, in Red Hat Atomic Host or its other versions, is one of many operating systems designed or optimized for containers. Others include:

To get Atomic Host up and running, an administrator must download an image of Atomic Host from Red Hat, create the VM using Red Hat's virt-manager tool, create a metadata ISO, attach init.iso to the virtual machine and start it, then enable the container orchestration technology Kubernetes and finally enable inter-container communications. There are other install options as well: For example, an Amazon Web Services customer can deploy the latest version of RHAH from an Amazon Machine Image.

Red Hat does offer OS and app management technologies for the bare-bones Atomic distribution, including a RHEL Atomic Tools container for debugging needs, and package layering technology to containerize persistent and dependency-laden apps. For example, a user can install the VMware Tools package so that Atomic Host will run better and faster with VMware-based environments.

Editor's note: Red Hat worked on a technology named Atomic Enterprise Platform that was never released. Atomic Enterprise Platform was an OpenShift project and unrelated to Atomic Host.

This was last updated in August 2017

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