Quick tips for the OpenShift oc client

23 mars 2021Jose Antonio Gonzalez Prada2 minutes (temps de lecture)

If you've played around with Kubernetes, you are aware of the rapid evolution of the most widely used container orchestration platform. Red Hat OpenShift is an enterprise-ready application platform built on Kubernetes and ready for production environments. With OpenShift 4, Red Hat aims to provide new releases at a frequent cadence. To help keep on top of all of the new changes, and to help sysadmins and DevOps people who have to deal with multiple versions of your Kubernetes platform at the same time, I wrote this article hoping to help you more easily overcome challenges you may face.

Our friend the `alternatives` command

The alternatives command creates, removes, maintains, and displays information about the symbolic links comprising the alternatives system.

From the man page:

The alternatives system is a reimplementation of the Debian alternatives system. It was rewritten primarily to remove the dependence on Perl; it is intended to be a drop-in replacement for Debian's update-dependencies script.

You can find a very good introduction to the command here on the Enable Sysadmin site: Introduction to the alternatives command in Linux.

After that brief introduction to the alternatives command, it's time to get to work.

[ You might also enjoy: A sysadmin's guide to basic Kubernetes components ]

The `oc` command

First, create the root directory for all your oc client versions. For example:

$ sudo mkdir -p /opt/openshift/client/

For each version you want to use or configure, do the following steps:

1. Create the folder and copy the binary for the version you choose:

    $ sudo mkdir /opt/openshift/client/x.y.z
    $ sudo cp /binary/path/x.y.z/oc /opt/openshift/client/x.y.z/

2. Create a new alternative:

    $ sudo alternatives --install /bin/oc oc /opt/openshift/client/x.y.z/oc 90

3. Next, select one of the versions you just configured. To do so, type the following:

    $ sudo alternatives --config oc

If you are one of those whose mantra is "do more with less," here's a little extra tip:

    $ alias oc_switch='sudo alternatives --config oc'

Want to know more about Linux aliases? See one of the following links from the Enable Sysadmin site:

OpenShift tips and tricks and Kubernetes tools

More oc tips are collected and explained by my friend Eduardo Minguez, Principal System Engineer at Red Hat, in his OpenShift 4 tips & tricks site, a collection of OpenShift 4 tips and tricks to make your container life easier.

Finally, I'd like to encourage you to attend the session 10 awesome Kubernetes tools every user should know presented by Alex Soto, Red Hat's Director of Developer Experience.

If you are new to OpenShift or not yet a pro user, the session will likely make your day.

[ Get this free ebook: Managing your Kubernetes clusters for dummies. ]

The following list provides additional tools, organized by the tool name and a link for more information, that you may wish to check out.