Docker DCA Online Practice Questions and Exam Preparation

Docker DCA Online Questions & Answers

• Question 11:

  Is this the purpose of Docker Content Trust? Solution: Sign and verify image tags.

  A. Yes
  B. No
  A. Yes

  ---

  Explanation/Reference:

  Signing and verifying image tags is the purpose of Docker Content Trust. Docker Content Trust (DCT) is a feature that allows you to use digital signatures for data sent to and received from remote Docker registries. These signatures allow client-side or runtime verification of the integrity and publisher of specific image tags. With DCT, image publishers can sign their images and image consumers can ensure that the images they pull are signed.

• Question 12:

  You want to create a container that is reachable from its host's network. Does this action accomplish this? Solution: Use network attach to access the containers on the bridge network

  A. Yes
  B. No
  B. No

  ---

  Explanation/Reference:

  Using network attach to access the containers on the bridge network does not make the container reachable from its host's network. The network attach option connects a running container to another network, but it does not expose any ports to the host. To make a container reachable from its host's network, you need to use either EXPOSE or --publish to access the containers on the bridge network.

• Question 13:

  Which of the following is supported by control groups?

  A. Manage certificates
  B. Collect net
  C. Limit CPU usage within a container
  D. Isolate processes in a container
  C. Limit CPU usage within a container

• Question 14:

  What is the difference between the ADD and COPY dockerfile instructions? (choosen 2)

  A. ADD supports compression format handling while COPY does not.
  B. COPY supports regular expression handling while ADD does not.
  C. COPY supports compression format handling while ADD does not.
  D. ADD support remote URL handling while COPY does not.
  E. ADD supports regular expression handling while COPY does not.
  D. ADD support remote URL handling while COPY does not.
  E. ADD supports regular expression handling while COPY does not.

• Question 15:

  Which flag for a service would allow a container to consume more than 2 GB of memory only when there is no memory contention but would also prevent a container from consuming more than 4GB of memory, in any case?

  A. --limit-memory 2GB --reserve-memory 4GB
  B. --limit-memory 4GB --reserve-memory 2GB
  C. --memory-swap 2GB --limit-memory 4GB
  D. --memory-swap 4GB --limit-memory 2GB
  C. --memory-swap 2GB --limit-memory 4GB

• Question 16:

  You are pulling images from a Docker Trusted Registry installation configured to use self-signed certificates, and this error appears:

  'x509: certificate signed by unknown authority'.

  You already downloaded the Docker Trusted Registry certificate authority certificate from https://dtr.example.com/ca.

  How do you trust it? (Select two.)

  A. Place the certificate in '/etc/docker/dtr/dtr.example.com.crt' and restart the Docker daemon on all cluster nodes.
  B. Place the certificate in your OS certificate path, trust the certificate system-wide, and restart the Docker daemon across all cluster nodes.
  C. Pass '-trust-certificate ca.crt' to the Docker client.
  D. Pass --insecure-registry to the Docker client.
  E. Place the certificate in '/etc/docker/certs.d/dtr.example com/ca.crt' on all cluster nodes.
  D. Pass --insecure-registry to the Docker client.
  E. Place the certificate in '/etc/docker/certs.d/dtr.example com/ca.crt' on all cluster nodes.

• Question 17:

  The following health check exists in a Dockerfile:

  'HEALTCHECK

  CMD curl --fail http://localhost/health || exit 1

  Which of the following describes its purpose?

  A. Defines the action taken when container health fails, which in this case will kill the container with exit status 1.
  B. Defines the health check endpoint on the localhost interface for external monitoring tools to monitor the health of the docker engine.
  C. Defines the health check endpoint on the local host interface for containers to monitor the health of the docker engine.
  D. Defines the health check for the containerized application so that the application health can be monitored by the Docker engine
  A. Defines the action taken when container health fails, which in this case will kill the container with exit status 1.

• Question 18:

  Is this an advantage of multi-stage builds?

  Solution: better caching when building Docker images

  A. Yes
  B. No
  B. No

  ---

  Explanation/Reference:

  Better caching when building Docker images is not an advantage of multi- stage builds. Multi-stage builds are a feature that allows you to use multiple FROM statements in a single Dockerfile. Each FROM statement begins a new stage of the

  build, with its own base image and instructions. You can selectively copy artifacts from one stage to another, leaving behind everything you don't want in the final image. The advantages of multi-stage builds are:

  Reducing the size of the final image by removing unnecessary dependencies or intermediate files.

  Improving the security of the final image by minimizing the attack surface and avoiding leaking secrets.

  Simplifying the development workflow by using different tools or environments in different stages. Better caching when building Docker images is not an advantage of multi-stage builds, as it depends on other factors, such as the order and

  content of the instructions in each stage, the availability and freshness of the base images and intermediate layers, and the use of build arguments or environment variables that may invalidate the cache.

• Question 19:

  Will this sequence of steps completely delete an image from disk in the Docker Trusted Registry? Solution: Delete the image and run garbage collection on the Docker Trusted Registry.

  A. Yes
  B. No
  A. Yes

  ---

  Explanation/Reference:

  Deleting the image and running garbage collection on the Docker Trusted Registry will completely delete the image from disk. According to the official documentation, this is the recommended way to remove images and reclaim disk space.

• Question 20:

  In the context of a swarm mode cluster, does this describe a node? Solution: an instance of the Docker engine participating in the swarm

  A. Yes
  B. No
  A. Yes