Free Docker DCA Exam Actual Questions

The questions for DCA were last updated On Nov 6, 2024

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Question No. 1

Your organization has a centralized logging solution, such as Splunk.

Will this configure a Docker container to export container logs to the logging solution?

Solution: docker logs

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Correct Answer: B

: = The commanddocker logs <container-id>will not configure a Docker container to export container logs to the logging solution, such as Splunk.This command only displays the logs of a specific container in the standard output or a file, but does not send them to any external system1.To export container logs to Splunk, you need to use the Docker Logger Drivers, which are plugins that provide logging capabilities for Docker containers2.The Splunk logging driver sends container logs to HTTP Event Collector in Splunk Enterprise and Splunk Cloud3.To use the Splunk logging driver for a specific container, you need to use the command-line flags--log-driverand--log-optwithdocker run, and provide the Splunk token and URL as options3. For example:

$ docker run --log-driver=splunk --log-opt splunk-token=VALUE --log-opt splunk-url=VALUE ...


docker logs | Docker Documentation

Logging drivers | Docker Documentation

Splunk logging driver | Docker Documentation

Question No. 2

Seven managers are in a swarm cluster.

Is this how should they be distributed across three datacenters or availability zones?

Solution: 5-1-1

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Correct Answer: B

= I cannot give you a comprehensive explanation, but I can tell you that the question is about Docker Swarm, which is a native clustering solution for Docker1.Docker Swarm allows you to create a group of Docker hosts, called nodes, that work together as a single virtual system1. Nodes can be either managers or workers.Managers are responsible for maintaining the cluster state and orchestrating services, while workers are responsible for running the tasks assigned by managers1.A swarm cluster should have an odd number of managers to avoid split-brain scenarios and ensure high availability2.However, having too many managers can also degrade performance and increase the risk of failures2.Therefore, the recommended number of managers is between 3 and 72. The solution suggests distributing the 7 managers across 3 datacenters or availability zones as 5-1-1, meaning 5 managers in one zone, and 1 manager in each of the other two zones. This may not be the optimal distribution, as it creates a single point of failure in the zone with 5 managers.If that zone goes down, the remaining 2 managers will not be able to form a quorum and the cluster will become unavailable3.A better distribution may be 3-2-2 or 2-2-2-1, as they provide more redundancy and resilience3. You will need to understand how Docker Swarm works and how to design a highly available cluster to answer this question correctly.Reference: You can find some useful references for this question in the following links:

Docker Swarm overview

Swarm mode key concepts

Swarm mode best practices


Question No. 3

Will this sequence of steps completely delete an image from disk in the Docker Trusted Registry?

Solution: Delete the image and delete the image repository from Docker Trusted Registry

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Correct Answer: B

Deleting the image and the image repository from Docker Trusted Registry will not completely delete the image from disk. This is because deleting a repository or a tag only removes the reference to the image, but not the image itself.The image is still stored as a blob on the disk, and can be accessed by its digest1.To completely delete the image from disk, you need to enable the deletion feature in the registry configuration, and then use the API to delete the image by its manifest2.Alternatively, you can manually delete the image files from the registry storage directory, but this is not recommended3.After deleting the image, you also need to run the garbage collector to reclaim the disk space4.Reference:

Docker Registry HTTP API V2

How to delete images from a private docker registry?

Remove docker image in registry by removing files/folders on server

Garbage collection


Question No. 4

You want to provide a configuration file to a container at runtime. Does this set of Kubernetes tools and steps accomplish this?

Solution: Turn the configuration file into a configMap object, use it to populate a volume associated with the pod, and mount that file from the volume to the appropriate container and path.

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Correct Answer: B

= Mounting the configuration file directly into the appropriate pod and container using the .spec.containers.configMounts key is not a valid way to provide a configuration file to a container at runtime.The .spec.containers.configMounts key does not exist in the Kubernetes API1.The correct way to provide a configuration file to a container at runtime is to use a ConfigMap2. A ConfigMap is a Kubernetes object that stores configuration data as key-value pairs. You can create a ConfigMap from a file, and then mount the ConfigMap as a volume into the pod and container.The configuration file will be available as a file in the specified mount path3.Alternatively, you can also use environment variables to pass configuration data to a container from a ConfigMap4.Reference:

PodSpec v1 core

Configure a Pod to Use a ConfigMap

Populate a Volume with data stored in a ConfigMap

Define Container Environment Variables Using ConfigMap Data


Question No. 5

A company's security policy specifies that development and production containers must run on separate nodes in a given Swarm cluster.

Can this be used to schedule containers to meet the security policy requirements?

Solution: label contraints

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Correct Answer: A

Label constraints can be used to schedule containers to meet the security policy requirements.Label constraints allow you to specify which nodes a service can run on based on the labels assigned to the nodes1. For example, you can label the nodes that are intended for development withenv=devand the nodes that are intended for production withenv=prod. Then, you can use the--constraintflag when creating a service to restrict it to run only on nodes with a certain label value.For example,docker service create --name dev-app --constraint 'node.labels.env == dev' ...will create a service that runs only on development nodes2.Similarly,docker service create --name prod-app --constraint 'node.labels.env == prod' ...will create a service that runs only on production nodes3. This way, you can ensure that development and production containers are running on separate nodes in a given Swarm cluster.Reference:

Add labels to swarm nodes

Using placement constraints with Docker Swarm

Multiple label placement constraints in docker swarm


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