CKAD-Exercises

CKAD Practice Questions: Container Management

Overview

Container management is a crucial skill for Kubernetes Application Developers. This section focuses on building, managing, and troubleshooting containers using tools like Docker and Podman.

Topics Covered

Practice Questions

1. Build and Push a Docker Image to a Container Registry

Scenario:

Details #### Dockerfile ```dockerfile FROM nginx:latest COPY index.html /usr/share/nginx/html/index.html ``` #### Steps Using Docker 1. Build the image: ```bash docker build -t my-nginx:1.0 . ``` 2. Tag the image for Docker Hub: ```bash docker tag my-nginx:1.0 /my-nginx:1.0 ``` 3. Push the image to Docker Hub: ```bash docker push /my-nginx:1.0 ``` #### Steps Using Podman 1. Build the image: ```bash podman build -t my-nginx:1.0 . ``` 2. Tag the image for Docker Hub: ```bash podman tag my-nginx:1.0 /my-nginx:1.0 ``` 3. Push the image to Docker Hub: ```bash podman push /my-nginx:1.0 ``` </details> --- ### 2. Pull and Save a Docker Image Locally **Scenario**: - Pull the official `busybox` image. - Save it locally as a `.tar` file for future use.
Details #### Steps Using Docker 1. Pull the image: ```bash docker pull busybox:latest ``` 2. Save the image as a `.tar` file: ```bash docker save busybox:latest -o busybox.tar ``` #### Steps Using Podman 1. Pull the image: ```bash podman pull docker.io/library/busybox:latest ``` 2. Save the image as a `.tar` file: ```bash podman save -o busybox.tar docker.io/library/busybox:latest ```
--- ### 3. Load a Saved Image into Your Local Environment **Scenario**: - Load the previously saved `busybox.tar` image into your local environment.
Details #### Steps Using Docker 1. Load the image: ```bash docker load -i busybox.tar ``` 2. Verify the image is loaded: ```bash docker images | grep busybox ``` #### Steps Using Podman 1. Load the image: ```bash podman load -i busybox.tar ``` 2. Verify the image is loaded: ```bash podman images | grep busybox ```
--- ### 4. Remove a Docker Image Locally **Scenario**: - Remove the `busybox` image from your local environment.
Details #### Steps Using Docker 1. Remove the image: ```bash docker rmi busybox:latest ``` 2. Verify the image is removed: ```bash docker images | grep busybox ``` #### Steps Using Podman 1. Remove the image: ```bash podman rmi docker.io/library/busybox:latest ``` 2. Verify the image is removed: ```bash podman images | grep busybox ```
--- ### 5. Retag an Existing Docker Image **Scenario**: - Retag the `busybox` image with a new tag and push it to a private container registry.
Details #### Steps Using Docker 1. Pull the image (if not already pulled): ```bash docker pull busybox:latest ``` 2. Retag the image: ```bash docker tag busybox:latest /busybox:custom-tag ``` 3. Push the image: ```bash docker push /busybox:custom-tag ``` #### Steps Using Podman 1. Pull the image (if not already pulled): ```bash podman pull docker.io/library/busybox:latest ``` 2. Retag the image: ```bash podman tag docker.io/library/busybox:latest /busybox:custom-tag ``` 3. Push the image: ```bash podman push /busybox:custom-tag ``` </details> --- ### 6. Clean Up Unused Images and Containers **Scenario**: - Identify and remove unused images and stopped containers from your environment.
Details #### Steps Using Docker 1. Remove unused images: ```bash docker image prune -f ``` 2. Remove stopped containers: ```bash docker container prune -f ``` #### Steps Using Podman 1. Remove unused images: ```bash podman image prune -f ``` 2. Remove stopped containers: ```bash podman container prune -f ```
--- ### 7. Build an Image with Multiple Tags **Scenario**: - Build a Docker image and assign it multiple tags during the build process.
Details #### Dockerfile ```dockerfile FROM alpine:latest RUN echo "Multi-tag example" ``` #### Steps Using Docker 1. Build the image with multiple tags: ```bash docker build -t my-app:latest -t my-app:v1.0 . ``` 2. Verify the tags: ```bash docker images | grep my-app ``` #### Steps Using Podman 1. Build the image with multiple tags: ```bash podman build -t my-app:latest -t my-app:v1.0 . ``` 2. Verify the tags: ```bash podman images | grep my-app ```
--- ### 8. Inspect Metadata of a Docker/Podman Image **Scenario**: - Inspect the metadata of the `nginx:latest` image and extract details such as the image ID, size, and environment variables.
Details #### Steps Using Docker 1. Pull the image (if not already pulled): ```bash docker pull nginx:latest ``` 2. Inspect the image: ```bash docker inspect nginx:latest ``` 3. Extract specific metadata (e.g., size): ```bash docker inspect nginx:latest --format='' ``` #### Steps Using Podman 1. Pull the image (if not already pulled): ```bash podman pull docker.io/library/nginx:latest ``` 2. Inspect the image: ```bash podman inspect docker.io/library/nginx:latest ``` 3. Extract specific metadata (e.g., size): ```bash podman inspect docker.io/library/nginx:latest --format='' ```
--- ### 9. Run a Temporary Container for Testing **Scenario**: - Run a temporary container using the `alpine` image to execute the `ping` command.
Details #### Steps Using Docker 1. Pull the image (if not already pulled): ```bash docker pull alpine:latest ``` 2. Run the container interactively: ```bash docker run --rm -it alpine:latest ping -c 4 google.com ``` #### Steps Using Podman 1. Pull the image (if not already pulled): ```bash podman pull docker.io/library/alpine:latest ``` 2. Run the container interactively: ```bash podman run --rm -it docker.io/library/alpine:latest ping -c 4 google.com ```
--- ### 10. Export a Running Container’s Filesystem **Scenario**: - Run a container using the `ubuntu` image, then export its filesystem to a `.tar` file.
Details #### Steps Using Docker 1. Run the container: ```bash docker run -d --name ubuntu-container ubuntu:latest tail -f /dev/null ``` 2. Export the filesystem: ```bash docker export ubuntu-container > ubuntu-container.tar ``` #### Steps Using Podman 1. Run the container: ```bash podman run -d --name ubuntu-container docker.io/library/ubuntu:latest tail -f /dev/null ``` 2. Export the filesystem: ```bash podman export ubuntu-container > ubuntu-container.tar ```
--- ### 11. Import a Filesystem as a New Image **Scenario**: - Import the exported `.tar` file as a new image named `custom-ubuntu`.
Details #### Steps Using Docker 1. Import the filesystem: ```bash cat ubuntu-container.tar | docker import - custom-ubuntu:latest ``` 2. Verify the image: ```bash docker images | grep custom-ubuntu ``` #### Steps Using Podman 1. Import the filesystem: ```bash cat ubuntu-container.tar | podman import - custom-ubuntu:latest ``` 2. Verify the image: ```bash podman images | grep custom-ubuntu ```
--- ### 12. Tag and Push an Image to a Private Registry **Scenario**: - Retag the `nginx` image and push it to a private registry running at `myregistry.local`.
Details #### Steps Using Docker 1. Pull the image (if not already pulled): ```bash docker pull nginx:latest ``` 2. Tag the image: ```bash docker tag nginx:latest myregistry.local/nginx:latest ``` 3. Push the image: ```bash docker push myregistry.local/nginx:latest ``` #### Steps Using Podman 1. Pull the image (if not already pulled): ```bash podman pull docker.io/library/nginx:latest ``` 2. Tag the image: ```bash podman tag docker.io/library/nginx:latest myregistry.local/nginx:latest ``` 3. Push the image: ```bash podman push myregistry.local/nginx:latest ```
--- ### 13. Prune Unused Images and Containers **Scenario**: - Remove all unused images and stopped containers from your environment.
Details #### Steps Using Docker 1. Prune unused images: ```bash docker image prune -a -f ``` 2. Prune stopped containers: ```bash docker container prune -f ``` #### Steps Using Podman 1. Prune unused images: ```bash podman image prune -a -f ``` 2. Prune stopped containers: ```bash podman container prune -f ```
--- ### 14. Run a Detached Container with Port Forwarding **Scenario**: - Run an NGINX container in detached mode and forward port 8080 on the host to port 80 in the container.
Details #### Steps Using Docker 1. Run the container: ```bash docker run -d -p 8080:80 nginx:latest ``` 2. Verify access: ```bash curl http://localhost:8080 ``` #### Steps Using Podman 1. Run the container: ```bash podman run -d -p 8080:80 docker.io/library/nginx:latest ``` 2. Verify access: ```bash curl http://localhost:8080 ```
--- ### 15. Use Build Arguments in a Dockerfile **Scenario**: - Create a Dockerfile for an Alpine-based image that accepts a build argument for a custom message.
Details #### Dockerfile ```dockerfile FROM alpine:latest ARG CUSTOM_MSG="Default Message" RUN echo "$CUSTOM_MSG" > /message.txt CMD cat /message.txt ``` #### Steps Using Docker 1. Build the image with a custom argument: ```bash docker build -t custom-alpine:latest --build-arg CUSTOM_MSG="Hello CKAD" . ``` 2. Run the container: ```bash docker run --rm custom-alpine:latest ``` #### Steps Using Podman 1. Build the image with a custom argument: ```bash podman build -t custom-alpine:latest --build-arg CUSTOM_MSG="Hello CKAD" . ``` 2. Run the container: ```bash podman run --rm custom-alpine:latest ```
--- ## **Notes and Tips** ### **Build** - Use `docker build` or `podman build` to create images. - Optimize image layers by ordering commands effectively in Dockerfiles. ### **Run** - Start containers with `docker run` or `podman run`. - Add flags for configuration: - `-d`: Run in detached mode. - `-p`: Map ports. - `--name`: Assign a name to the container. ### **Pull & Push** - Pull images with `docker pull ` or `podman pull `. - Push images to a registry using `docker push ` or `podman push `. ### **Save** - Save images locally with `docker save -o ` or `podman save`. ### **Debug** - Use commands like `docker logs ` or `podman logs` for debugging. - Inspect container metadata with `docker inspect ` or `podman inspect`. ### **Remove** - Delete images or containers: - `docker rmi ` or `podman rmi` for images. - `docker rm ` or `podman rm` for containers. --- ## **Resources** 1. [Docker Documentation](https://docs.docker.com/) 2. [Podman Documentation](https://podman.io/) 3. [Kubernetes Official Documentation](https://kubernetes.io/docs/)