Articles by Thomas Jungbauer

Imagine you have one OpenShift cluster and you would like to create 2 or more environments inside this cluster, but also separate them and force the environments to specific nodes, or use specific inbound routers. All this can be achieved using labels, IngressControllers and so on. The following article will guide you to set up dedicated compute nodes for infrastructure, development and test environments as well as the creation of IngressController which are bound to the appropriate nodes.

Red Hat Advanced Cluster Security (RHACS) Central is installed with one administrator user by default. Typically, customers request an integration with existing Identity Provider(s) (IDP). RHACS offers different options for such integration. In this article 2 IDPs will be configured as an example. First OpenShift Auth and second Red Hat Single Sign On (RHSSO) based on Keycloak

You should always follow the Best Practices and Ansible Lint rules defined by the Ansible documentation when developing playbooks.

Although very basic, the Best Practices document gives a few guidelines to be able to carry out well-structured playbooks and roles, it contains recommendations that evolve with the project, so it is recommended to review it regularly. It is advisable to review the organization of content in Ansible.

The Ansible Lint documentation shows us through this tool the syntax rules that will be checked in the testing of roles and playbooks, the rules that will be checked are indicated in this document in their respective section.

The following article shall quickly, without huge background information, deploy an Identity Management Server (based on FreeIPA) and connect this IDM to an existing Automation Controller so authentication can be tested and verified based on LDAP.

Working with a GitOps approach is a good way to keep all configurations and settings versioned and in sync on Git. Sensitive data, such as passwords to a database connection, will quickly come around. Obviously, it is not a idea to store clear text strings in a, maybe even public, Git repository. Therefore, all sensitive information should be stored in a secret object. The problem with secrets in Kubernetes is that they are actually not encrypted. Instead, strings are base64 encoded which can be decoded as well. Thats not good …​ it should not be possible to decrypt secured data. Sealed Secret will help here…​

Pod scheduling is an internal process that determines placement of new pods onto nodes within the cluster. It is probably one of the most important tasks for a Day-2 scenario and should be considered at a very early stage for a new cluster. OpenShift/Kubernetes is already shipped with a default scheduler which schedules pods as they get created accross the cluster, without any manual steps.

However, there are scenarios where a more advanced approach is required, like for example using a specifc group of nodes for dedicated workload or make sure that certain applications do not run on the same nodes. Kubernetes provides different options:

This series will try to go into the detail of the different options and explains in simple examples how to work with pod placement rules. It is not a replacement for any official documentation, so always check out Kubernetes and or OpenShift documentations.

Node Affinity allows to place a pod to a specific group of nodes. For example, it is possible to run a pod only on nodes with a specific CPU or disktype. The disktype was used as an example for the nodeSelector and yes …​ Node Affinity is conceptually similar to nodeSelector but allows a more granular configuration.

One of the easiest ways to tell your Kubernetes cluster where to put certain pods is to use a nodeSelector specification. A nodeSelector defines a key-value pair and are defined inside the specification of the pods and as a label on one or multiple nodes (or machine set or machine config). Only if selector matches the node label, the pod is allowed to be scheduled on that node.

While noteSelector provides a very easy way to control where a pod shall be scheduled, the affinity/anti-affinity feature, expands this configuration with more expressive rules like logical AND operators, constraints against labels on other pods or soft rules instead of hard requirements.

The feature comes with two types:

While Node Affinity is a property of pods that attracts them to a set of nodes, taints are the exact opposite. Nodes can be configured with one or more taints, which mark the node in a way to only accept pods that do tolerate the taints. The tolerations themselves are applied to pods, telling the scheduler to accept a taints and start the workload on a tainted node.

A common use case would be to mark certain nodes as infrastructure nodes, where only specific pods are allowed to be executed or to taint nodes with a special hardware (i.e. GPU).