Skip to main content

RHCA - EX180/EX280

Red Hat Certified Specialist in Containers and Kubernetes

Notes, tips and tricks for the EX180 and EX280 exams.


Podman host setup

dnf module install container-tools
dnf install -y buildah

Podman basics

Registry file: /etc/containers/registries.conf

Login to a registry

podman login

Search for images

podman search mariadb

Inspect images without downloading

skopeo inspect docker://

Download images

podman pull

List images

podman images

Inspect images. *Useful for locating config.user

podman inspect

Configure container volume path

sudo mkdir /srv/mariadb
sudo chown -R 27:27 /srv/mariadb # UID found in podman inspect
sudo semanage fcontext -a -t container_file_t "/srv/mariadb(/.*)"
sudo restorecon -Rv /srv/mariadb

Run image
-d detached
-e per variable
-p local_port:container_port
-v local/path:/path/in/pod

podman run -d -e MYSQL_USER=user \
-p 33306:3306  \
-v /srv/mariadb:/var/lib/mysql:Z \ # :Z isn't needed if SELinux manually configured

Basic pod status and names

podman ps


Enter container in interactive shell

podman exec -it container-name /bin/bash

Commit changes to running image

podman commit container-name image-name

Export image

podman save image-name > /path/to/image.tar

Remove images

podman rmi image-name --force

Restore/Load image

podman load -i /path/to/image.tar

Dockerfile Basics

Container for scanning a network.

# Start with a base image
# Maintainer information
MAINTAINER ClusterApps <>
# Run commands to build the container
# Do as much with the fewest RUN lines
RUN yum --assumeyes update && \
yum --assumeyes install \
nmap iproute procps-ng && \
bash && \
yum clean all
# Entrypoint is the command that run when the ccontainer starts
ENTRYPOINT ["/usr/bin/nmap"]
#  The arguments for the entrypoint
CMD ["-sn", ""]

Build the image with a tag

podman build -t notes180 .

List images

podman images

Run the image

podman run localhost/notes180

OpenShift Basics

Setup oc completion

source <(oc completion bash)

Create a new project

oc new-project nginx

Create a new application based on an image

oc new-app bitnami/nginx

Basic information about the project

oc status



Get more detailed information about the project

oc get all


Get full details about a pod

oc describe pod/nginx-84654f9574-9gpnt

Get full details about a deployment

oc describe deployment.apps/nginx

Application deployments

Generate a YAML file to use as a base.

oc create deployment nginx --image=bitnami/nginx --dry-run=client -o yaml > newapp.yml

Create a temporary deployment using the YAML file,

oc create -f newapp.yml

Create the service by exposing the deployment

# dry run to add to YAML file
oc expose deployment --port=8080 --dry-run=client nginx -o yaml >> newapp.yml
# run to create the service
oc expose deployment --port=8080 nginx

Expose the service

oc expose svc nginx --dry-run=client -o yaml >> newapp.yml

New app with parameters, as a deployment-config, and with labels (app=database)

oc new-app --name mdb -l app=database -e MYSQL_USER=dbuser -e MYSQL_PASSWORD=SuperAwesomePassword -e MYSQL_DATABASE=dbname bitnami/mysql --as-deployment-config

Delete the temporary application

oc delete all --all

Edit the YAML file and break up the sections into proper YAML.
Add --- at the beginning of a section
Add ... at the end of a section.

The new nginx app YAML file.

apiVersion: apps/v1
kind: Deployment
  creationTimestamp: null
    app: nginx
  name: nginx
  replicas: 1
      app: nginx
  strategy: {}
      creationTimestamp: null
        app: nginx
      - image: bitnami/nginx
        name: nginx
        resources: {}
status: {}

apiVersion: v1 kind: Service metadata: creationTimestamp: null labels: app: nginx name: nginx spec: ports:

  • port: 8080 protocol: TCP targetPort: 8080 selector: app: nginx status: loadBalancer: {} ...

apiVersion: kind: Route metadata: creationTimestamp: null labels: app: nginx name: nginx spec: port: targetPort: 8080 to: kind: "" name: nginx weight: null status: {} ...

Delete API resources defined by a YAML file.

oc delete -f newapp.yml

Using Templates

Get a list of templates

oc get templates -n openshift

Get template details
Review the parameters section for a list of environment variables.

oc describe template -n openshift mariadb-persistent

Create a new application from a template

oc new-app --template=mariadb-persistent \
-p MYSQL_USER=jack -p MYSQL_PASSWORD=password \

Check the status of the deployment.

oc get all
oc describe pod/mariadb-1-qlvrj

Source 2 Image

Gety a list of templates and streams

oc new-app -L

Deploy a new app from a git repo

oc new-app php~

Watch the app get built

oc logs -f buildconfig/simpleapp

Review the deployment with oc get all

NAME                            READY   STATUS      RESTARTS   AGE
pod/mariadb-1-deploy            0/1     Completed   0          16m
pod/mariadb-1-qlvrj             1/1     Running     0          16m
pod/simpleapp-1-build           0/1     Completed   0          2m10s
pod/simpleapp-fb5554fd9-4kgnb   1/1     Running     0          89s

NAME DESIRED CURRENT READY AGE replicationcontroller/mariadb-1 1 1 1 16m

NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE service/mariadb ClusterIP <none> 3306/TCP 16m service/simpleapp ClusterIP <none> 8080/TCP,8443/TCP 2m11s

NAME READY UP-TO-DATE AVAILABLE AGE deployment.apps/simpleapp 1/1 1 1 2m11s

NAME DESIRED CURRENT READY AGE replicaset.apps/simpleapp-75c686cbb8 0 0 0 2m11s replicaset.apps/simpleapp-fb5554fd9 1 1 1 89s

NAME REVISION DESIRED CURRENT TRIGGERED BY 1 1 1 config,image(mariadb:10.3-el8)


NAME TYPE FROM STATUS STARTED DURATION Source Git@26e2f16 Complete 2 minutes ago 41s

NAME IMAGE REPOSITORY TAGS UPDATED default-route-openshift-image-registry.apps-crc.testing/nginx2/simpleapp latest About a minute ago