Notes of a workshop where I showed my team (Packit) how I work with CodeReady Containers and OpenShift.

CRC #

Installation: follow the steps to download, setup and run a CodeReady Containers cluster. You need a Red Hat account to log in and access the page. Reading through the docs might save some time with fixing issues.

Unpack the executable from the archive to somewhere in your PATH. I have it in ~/.local/bin.

The pull secret needs to be entered during the first crc start.

I need to run:

$ sudo systemctl start libvirtd

… before starting the cluster, but couldn’t figure it out why 😕

crc commands are similar to the ones from minishift. Use crc --help to learn more about them.

While working on dist2src, the deployment kept running out of memory, especially during re-deployments. Raising the memory available for the CRC-cluster solved this issue:

crc start --memory 10240

The Starting OpenShift cluster... step is going to take minutes. Go get a ☕.

Once the cluster is up, just follow the instructions:

To access the cluster, first set up your environment by following 'crc oc-env' instructions.
Then you can access it by running 'oc login -u developer -p developer https://api.crc.testing:6443'.
To login as an admin, run 'oc login -u kubeadmin -p dpDFV-xamBW-kKAk3-Fi6Lg https://api.crc.testing:6443'.
To access the cluster, first set up your environment by following 'crc oc-env' instructions.

You can now run 'crc console' and use these credentials to access the OpenShift web console.

Personally, I didn’t find the need to use the crc oc-env part, ever, oc available on Fedora works just fine, but if I would ever hit strange issues when interacting with the cluster, this would be the first thing to try in order to fix them.

OpenShift #

Run oc project to tell which project and cluster is active. For switching between them, I use a context switcher script.

Working with pods #

oc get pods will list pods in the project and their status. The -w flag can be used to enter watch mode, but I find running watch -n5 oc get pods in a tmux-pane of it’s own much more intuitive.

In general, I use tmux-panes to set up a dashboard to work with a project, in case I plan to stay in the terminal.

oc describe pod <POD> shows all you need to know about a pod. But for this, I actually prefer to use the web-console 😅.

oc logs -f [pod/]<POD> to stream the logs. But the pod name will change (most of the time) when things are redeployed. So an alternative is to follow the logs for the deployment config with oc logs -f dc/<DEPLOYMENTCONFIG>.

Working with other resources #

oc get <RESOURCE> - to list things.

oc edit <RESOURCE> - to edit those things.

A resource can a ConfigMap (cm), DeploymentConfig (dc), Secret (secret) and so on. See oc types for a full list.

Don’t forget that editing ConfigMaps and Secrets doesn’t always redeploy the pods that are using them, so you might need to do this manually.

$ oc rollout latest dc/<NAME>

Defining objects #

oc explain is great for getting some help and understanding OpenShift YAML.

$ oc explain sts.spec.template.spec.containers.envFrom
KIND:     StatefulSet
VERSION:  apps/v1

RESOURCE: envFrom <[]Object>

DESCRIPTION:
     List of sources to populate environment variables in the container. The
     keys defined within a source must be a C_IDENTIFIER. All invalid keys will
     be reported as an event when the container is starting. When a key exists
     in multiple sources, the value associated with the last source will take
     precedence. Values defined by an Env with a duplicate key will take
     precedence. Cannot be updated.

     EnvFromSource represents the source of a set of ConfigMaps

FIELDS:
   configMapRef <Object>
     The ConfigMap to select from

   prefix       <string>
     An optional identifier to prepend to each key in the ConfigMap. Must be a
     C_IDENTIFIER.

   secretRef    <Object>
     The Secret to select from