Welcome to Yet Another Useless Blog
Despite the name, we hope you'll find these articles genuinely helpful! 😊
Who are we?
We're Thomas Jungbauer and Toni Schmidbauer — two seasoned IT professionals with over 20 years of experience each. Currently, we work as architects at Red Hat Austria, helping customers design and implement OpenShift and Ansible solutions.
What's this blog about?
Real-world problems, practical solutions. We document issues we've encountered in the field along with step-by-step guides to reproduce and resolve them. Our goal: save you hours of frustrating documentation searches and trial-and-error testing.
Feel free to send us an e-mail or open a GitHub issue.
Recent Posts
Using Descheduler
Thomas Jungbauer
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:
nodes are under/over-utilized
pod or node affinity, taints or labels have changed and are no longer valid for a running pod
node failures
pods have been restarted too many times
Ansible Tower and downloading collections
Toni Schmidbauer
Every wondered why Ansible Tower does not start downloading required collections when you synchronize a project? Here are the stumbling blocks we discovered so far:
oc compliance command line plugin
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.
Compliance Operator
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/.
Understanding RWO block device handling in OpenShift
In this blog post we would like to explore OpenShift / Kubernetes block device handling. We try to answer the following questions:
What happens if multiple pods try to access the same block device?
What happens if we scale a deployment using block devices to more than one replica?
Writing Operator using Ansible
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.
Thanos Querier vs Thanos Querier
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.
GitOps - Argo CD
Argo CD is a declarative, GitOps continuous delivery tool for Kubernetes. GitOps itself uses Git pull request to manager infrastructure and application configuration.
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