Linux Foundation CKAD 問題集

質問 1：
You have a Deployment named 'wordpress-deployment' that runs 3 replicas of a WordPress container. You want to ensure that the deployment is always updated with the latest image available in the 'wordpress/wordpress:latest' Docker Hub repository However, you need to implement a rolling update strategy that allows for a maximum ot two pods to be unavailable during the update process.
正解：
See the solution below with Step by Step Explanation.
Explanation:
Solution (Step by Step) :
1. IJpdate the Deployment YAML:
- Update the 'replicas to 3-
- Define 'maxunavailable: 2 and 'maxSurge: in the 'strategy.rollingupdate' section.
- Configure a 'strategy-type' to 'RollinglJpdate' to trigger a rolling update when the deployment is updated.
- Add a 'spec-template-spec-imagePullPolicy: Always' to ensure that the new image is pulled even if it exists in the pod's local cache.

2. Create the Deployment: - Apply the updated YAML file using 'kubectl apply -f wordpress-deployment.yamr 3. Verify the Deployment: - Check tne status of the deployment using 'kubectl get deployments wordpress-deployment' to confirm the rollout and updated replica count. 4. Trigger the Automatic Update: - Push a new image to the 'wordpress/wordpress:latest Docker Hub repository. 5. Monitor the Deployment: - Use 'kubectl get pods -I app=wordpress' to monitor the pod updates during the rolling update process. You will observe that two pods are terminated at a time, while two new pods with the updated image are created. 6. Check for Successful Update: - Once the deployment is complete, use 'kubectl describe deployment wordpress-deployment' to see that the 'updatedReplicaS field matches the 'replicas' field, indicating a successful update.

質問 2：
You are working on a Kubernetes application that uses Kustomize to manage its configuratiom You have multiple environments (development, staging, production) and you want to use Kustomize to easily adjust the application's resources based on the target environment. While debugging, you realized that some of the configurations are not being applied correctly. How can you effectively debug Kustomize issues and pinpoint where the configuration is failing?
正解：
See the solution below with Step by Step Explanation.
Explanation:
Solution (Step by Step) :
I). Enable Kustomize Logging:
- Add the '--loglever flag to your 'kustomize' command to enable debug-level logging.
- Example: 'kustomize -loglevel debug
- This will provide detailed information about Kustomize's operations, including the resources being processed and the transformations being applied.
2. Inspect the Kustomization File ('kustomization.yaml'):
- Examine the 'kustomization.yamr file for any typos, invalid paths, or incorrect configuration options.
- Verify that the 'patches' and 'patchesStrategicMerge' sections correctly reference the desired patches.
- Ensure that the 'resources' section lists all the necessary files or directories.
3. Utilize Kustomize's 'build' Command:
- The 'kustomize build' command can be used to generate the final Kubemetes manifests before applying them to your cluster.
- This allows you to inspect the generated manifests and identify any issues in the configuration.
- Example: 'kustomize build
4. Isolate the Issue with Patches:
- If you suspect a specific patch is causing the issue, comment out or remove the patch from the 'kustomization.yamr file-
- Rebuild the manifests with the 'kustomize build' command and observe the output.
- This will help determine if the patch is the root cause of the problem-
5. Use Kustomize's 'edit' Command.
- Kustomize provides an 'edit' command that can be used to interactively modify the configuration.
- Example: 'kustomize edit set image deployment/nginx-deployment nginx:12.3
- This allows you to directly modify the resources and observe how Kustomize applies the changes.
6. Leverage Kustomize's 'version' Command:
- The 'kustomize version' command will show you the current version of Kustomize you are using.
- This is helpful for troubleshooting potential compatibility issues or understanding if there have been recent updates that might have introduced changes.
7. Refer to Kustomize Documentation:
- The official Kustomize documentation provides detailed explanations, examples, and troubleshooting guides. - [https://kustomize.io/l(https://kustomize.io/)
8. Debug the Underlying Kubernetes Resources:
- If you are still encountering issues after investigating Kustomize, it's important to debug the underlying Kubernetes resources themselves.
- Use tools like ' kubectl describe' or 'kubectl logs' to analyze the resources and their associated pods.
9. Check for Conflicts:
- Be aware of potential conflicts between different Kustomize configurations if you are applying multiple "kustomization.yaml' files.
- Ensure that your configurations do not overwrite each other's settings unintentionally.
10. Test Thoroughly:
- After making any changes to your Kustomize configuration, it is essential to test the changes thoroughly in your target environments.
- Verify that your application behaves as expected and that all the desired configurations are applied correctly. ,

質問 3：
You have a Node.js application that runs in a Kubernetes cluster. The application requires access to a MySQL database hosted externally on a different server. Due to security concerns, you cannot directly expose the database to the application pod. Describe how you can implement a network policy to enable secure communication between the application pod and the MySQL database.
正解：
See the solution below with Step by Step Explanation.
Explanation:
Solution (Step by Step) :
1. Create a Network Policy:
- Create a Network Policy that allows traffic only from the application pods to the MySQL database server-
- Define the podSelector' to specify the application pods that should be allowed to connect to the database.
- Use 'ingress' rules to define the allowed incoming traffic from the application pods.
- Specify the 'from' field to identify the source pods using labels or namespaces-
- Set the 'to' field to specify the target IP address or range of the MySQL database server

2. Deploy the Network Policy: - Apply the Network Policy to your Kubernetes cluster using 'kubectl apply -f mysql-access.yamr 3. Configure the Application: - Configure your Node.js application to connect to the MySQL database using the IP address or hostname of the database server. - Ensure that the Node.js application has appropriate security credentials to access the database. 4. Test the Application: - Run your application and verify that it can connect to the MySQL database successfully. Note: This example provides a basic implementation. You might need to adjust the configuration based on your specific security requirements and network setup. You can further enhance the network policy by using specific ports, protocols, and other security measures as needed.,

質問 4：
You nave a microservice tnat iS constantly updated With new features and bug fixes. You want to deploy new versions of this service in a way that minimizes downtime and avoids disrupting the existing application. Explain how you can use Kubernetes features to achieve this goal.
正解：
See the solution below with Step by Step Explanation.
Explanation:
Solution (Step by Step) :
1. Use a Deployment:
- Create a 'Deployment' object to manage your microservice.
- Specify the desired number of replicas and the container image.
- Use a 'rollinglJpdate' strategy to control the update process.

2. Control Rollout Pace: - Use the maxSurge' and 'maxlJnavailable' parameters to control the number of pods that can be unavailable or created during the update process. - For example, 'maxi-Inavailable: ensures that no pods are unavailable during tne update, while 'maxSurge: 1' allows for one extra pod to be created during the update. 3. Trigger Automatic Updates: - Use a 'Deployment's 'spec-template-spec-imagePullPolicy' to trigger updates automatically when a new image is available. - Set imagePullPolicy: Always' to force a pull of the image each time the deployment is updated. 4. Monitor Rollout Progress: - Use kubectl get pods -l app=my-microservice' to monitor the rollout progress. - You can also use tne 'kubectl rollout status deployment/my-microservice' command to get detailed information about the rollout. 5. Use Liveness and Readiness Probes: - Define liveness and readiness probes to ensure that containers are healthy and ready to serve traffic. - The 'Deployment' will automatically restart unhealthy containers, while readiness probes will ensure that new pods are only considered ready for traffic once they are healtny. 6. Traffic Routing: - Use a 'Service' to expose your 'Deployment' to external clients. - Configure the 'Service' to use a 'LoadBalancer' or 'NodePort' to make the service accessible from outside the cluster. Note: This approach ensures a smooth rollout with minimal downtime. New pods are created with the new image, and traffic is gradually shifted to the updated pods while the old pods are gracefully terminated. The liveness and readiness probes ensure that only healthy pods receive traffic, and the automatic updates triggered by 'imagePullPolicy: Always' keep the service up-to-date.

質問 5：
You are building a system for scheduling daily backups of a critical database. The backup process involves running a script that connects to the database, extracts tne data, and saves it to an S3 bucket. How would you utilize Kubernetes JobS to automate this backup process and ensure it runs every day at 2:00 AM?
正解：
See the solution below with Step by Step Explanation.
Explanation:
Solution (Step by Step) :
1. Create a Job YAML file.

- Replace 'your-backup-script-image:latest With the actual image name of your backup script. - Replace 'your-backup-script.sn' with the actual name Of your backup script. - Replace saws-secret' with the name of the Kubernetes secret holding your AWS credentials (see step 2). - 'restartPolicy: Never ensures the job runs only once. 2. Create a Secret for AWS Credentials:

- Replace ''and'' With your actual AWS credentials. 3. Create a CronJob YAML file:

- Adjust the 'schedules to your desired daily execution time. - Ensure the 'jobTemplate' matches the Job YAML definition. 4. Apply the YAML files: - Use 'kubectl apply -f job.yamr and 'kubectl apply -f cronjob.yamr to create the Job and CronJob on your cluster 5. Verify the CronJob: - Use ' kubectl get cronjobs' to check the status of the CronJob- - You should see the CronJob running and triggering the Job at the specified time.