OpenShift

Topology spread constraints is a new feature since Kubernetes 1.19 (OpenShift 4.6) and another way to control where pods shall be started. It allows to use failure-domains, like zones or regions or to define custom topology domains. It heavily relies on configured node labels, which are used to define topology domains. This feature is a more granular approach than affinity, allowing to achieve higher availability.

Descheduler is a new feature which is GA since OpenShift 4.7. It can be used to evict pods from nodes based on specific strategies. The evicted pod is then scheduled on another node (by the Scheduler) which is more suitable.

This feature can be used when:

As described at Compliance Operator the Compliance Operator can be used to scan the OpenShift cluster environment against security benchmark, like CIS. Fetching the actual results might be a bit tricky tough.

With OpenShift 4.8 plugins to the oc command are allowed. One of these plugin os oc compliance, which allows you to easily fetch scan results, re-run scans and so on. Let’s install and try it out.

OpenShift comes out of the box with a highly secure operating system, called Red Hat CoreOS. This OS is immutable, which means that no direct changes are done inside the OS, instead any configuration is managed by OpenShift itself using MachineConfig objects. Nevertheless, hardening certain settings must still be considered. Red Hat released a hardening guide (CIS Benchmark) which can be downloaded at https://www.cisecurity.org/.

In this blog post we would like to explore OpenShift / Kubernetes block device handling. We try to answer the following questions:

This quick post shall explain, without any fancy details, how to write an Operator based on Ansible. It is assumed that you know what purpose an Operator has.

As a short summary: Operators are a way to create custom controllers in OpenShift or Kubernetes. It watches for custom resource objects and creates the application based on the parameters in such custom resource object. Often written in Go, the SDK supports Ansible, Helm and (new) Java as well.

OpenShift comes per default with a static Grafana dashboard, which will present cluster metrics to cluster administrators. It is not possible to customize this Grafana instance.

However, many customers would like to create their own dashboards, their own monitoring and their own alerting while leveraging the possibilities of OpenShift at the same time and without installing a completely separated monitoring stack.

Argo CD is a declarative, GitOps continuous delivery tool for Kubernetes. GitOps itself uses Git pull request to manager infrastructure and application configuration.