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Understanding OpenShift sandboxed containers

OpenShift sandboxed containers support for OpenShift Container Platform provides users with built-in support for running Kata Containers as an additional optional runtime. This is particularly useful for users who are wanting to perform the following tasks:

  • Run privileged or untrusted workloads.

  • Ensure kernel isolation for each workload.

  • Share the same workload across tenants.

  • Ensure proper isolation and sandboxing for testing software.

  • Ensure default resource containment through VM boundaries.

OpenShift sandboxed containers also provides users the ability to choose from the type of workload that they want to run to cover a wide variety of use cases.

You can use the OpenShift sandboxed containers Operator to perform tasks such as installation and removal, updates, and status monitoring.

Sandboxed containers are only supported on bare metal.

Red Hat Enterprise Linux CoreOS (RHCOS) is the only supported operating system for OpenShift sandboxed containers 1.0.0.

OpenShift sandboxed containers common terms

The following terms are used throughout the documentation.

Sandbox

A sandbox is an isolated environment where programs can run. In a sandbox, you can run untested or untrusted programs without risking harm to the host machine or the operating system.

In the context of OpenShift sandboxed containers, sandboxing is achieved by running workloads in a different kernel using virtualization, providing enhanced control over the interactions between multiple workloads that run on the same host.

Pod

A pod is a construct that is inherited from Kubernetes and OpenShift Container Platform. It represents resources where containers can be deployed. Containers run inside of pods, and pods are used to specify resources that can be shared between multiple containers.

In the context of OpenShift sandboxed containers, a pod is implemented as a virtual machine. Several containers can run in the same pod on the same virtual machine.

OpenShift sandboxed containers Operator

An Operator is a software component that automates operations, which are actions that a human operator could do on the system.

The OpenShift sandboxed containers Operator is tasked with managing the lifecycle of sandboxed containers on a cluster. It deals with operations, such as the installation and removal of sandboxed containers software and status monitoring.

Kata Containers

Kata Containers is a core upstream project that is used to build OpenShift sandboxed containers. OpenShift sandboxed containers integrate Kata Containers with OpenShift Container Platform.

KataConfig

KataConfig objects represent configurations of sandboxed containers. They store information about the state of the cluster, such as the nodes on which the software is deployed.

RHCOS extensions

Red Hat Enterprise Linux CoreOS (RHCOS) extensions are a mechanism to install optional OpenShift Container Platform software. The OpenShift sandboxed containers Operator uses this mechanism to deploy sandboxed containers on a cluster.

Runtime class

A RuntimeClass object describes which runtime can be used to run a given workload. A runtime class that is named kata is installed and deployed by the OpenShift sandboxed containers Operator. The runtime class contains information about the runtime that describes resources that the runtime needs to operate, such as the pod overhead.

OpenShift sandboxed containers building blocks

The OpenShift sandboxed containers Operator encapsulates all of the components from Kata containers. It manages installation, lifecycle, and configuration tasks.

The OpenShift sandboxed containers Operator is packaged in the Operator bundle format as two container images. The bundle image contains metadata and is required to make the operator OLM-ready. The second container image contains the actual controller that monitors and manages the KataConfig resource.

RHCOS extensions

The OpenShift sandboxed containers Operator is based on the Red Hat Enterprise Linux CoreOS (RHCOS) extensions concept. The sandboxed containers RHCOS extension contains RPMs for Kata, QEMU, and its dependencies. You can enable them by using the MachineConfig resources that the Machine Config Operator provides.

Additional resources