Once an application is deployed, we don’t think about the operating system much - unless it breaks. This is even more true for containerized applications, whether they’re deployed to a single host using Podman or across a Kubernetes cluster. But even though the operating system is mostly ignored by the application team, it plays an important role for administrators and can dramatically affect our experience.

OpenShift 4 introduced a significant shift in how Red Hat deploys and manages the operating system underpinning everything else in OpenShift, changing from Red Hat Enterprise Linux (RHEL), and sometimes RHEL Atomic, to Red Hat Enterprise Linux CoreOS (RHCOS).

This episode we welcome Mark Russell, product manager, and Derrick Ornelas, product experience engineer, to talk about why and how RHCOS is different, along with discussing some configuration options for manageability, performance, and resiliency.

As always, please see the list below for additional links to specific topics, questions, and supporting materials for the episode!

If you’re interested in more streaming content, please subscribe to the OpenShift.tv streaming calendar to see the upcoming episode topics and to receive any schedule changes. If you have questions or topic suggestions for the Ask an OpenShift Admin Office Hour, please contact us via Discord, Twitter, or come join us live, Wednesdays at 11am EDT / 1500 UTC, on YouTube and Twitch.

Episode 28 recorded stream:


Supporting links for today:

  • Use this link to jump directly to where we start talking about today’s topic
  • We were absent the last two weeks as a result of Red Hat Summit, GitOpsCon, OpenShift Commons, and KubeCon EMEA. We have some great summaries of each of those events at the links, so if you’re curious what we were doing be sure to give them a read!
  • Deploying an OpenShift cluster across multiple sites, for example having control plane nodes in three different datacenters, is possible, but there are some important things you should know and prepare for. This KCS provides some guidelines and recommendations if you choose to pursue multi-site OpenShift.
  • Updates / upgrades to OpenShift 4.7 are available now! If you have deployed your OpenShift cluster to vSphere using a non-integrated, platform agnostic (a.k.a. bare metal UPI or simply set platform=none in the install-config.yaml), then you’ll want to pay special attention to the known issues! Due to a bug between VXLAN offload and the RHEL 8.3 kernel used by RHCOS in OpenShift 4.7, there can be some packet loss occurring. The workaround in the release notes is to use VM hardware version 13, but if you’re using a newer version you can also apply machine config to disable the offload and workaround the issue that way.
  • Did you know that you can change the domain name used for Routes? Setting an appsDomain on the Ingress configuration will cause all Routes to use the configured domain instead of the default. FYI, the docs say it’s AWS only, but that’s incorrect (and there’s a BZ to fix it) - the option is supported with any deployment type!
  • Last, but not least, following up from when Katherine Dubé was on the stream to talk about installation methods, there’s now a blog post which shows how to manually add nodes to vSphere IPI clusters.

Questions answered during the stream:


How-tos, Videos, Red Hat CoreOS, OpenShift.tv, Linux

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