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Free Practice Questions for Docker DCA Exam

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Total 191 questions

Question 1

Is this statement correct?

Solution: A Dockerfile stores the Docker daemon's configuration options.



Answer : B

The statement isnotcorrect. A Dockerfile does not store the Docker daemon's configuration options.A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image1. A Dockerfile is used to build images, not to configure the Docker daemon.The Docker daemon's configuration options are stored in a JSON file, which is usually located at /etc/docker/daemon.json on Linux systems, or C:\ProgramData\docker\config\daemon.json on Windows2.The JSON file allows you to customize the Docker daemon's behavior, such as enabling debug mode, setting TLS certificates, or changing the data directory2.Reference:Dockerfile reference),Docker daemon configuration overview)


Question 2

Seven managers are in a swarm cluster.

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

Solution: 4-2-1



Answer : B

= This is not how the seven managers should be distributed across three datacenters or availability zones.A swarm cluster is a group of Docker hosts that are running in swarm mode and act as managers or workers1.A manager node is responsible for maintaining the swarm state and orchestrating the services2.A swarm cluster needs a quorum of managers to operate, which means a majority of managers must be available and able to communicate with each other3.

The problem with distributing the seven managers as 4-2-1 is that it creates a split-brain scenario, where the cluster can lose the quorum if one datacenter or availability zone fails. For example, if the datacenter with four managers goes down, the remaining three managers will not have enough votes to form a quorum, and the cluster will stop functioning.Similarly, if the datacenter with one manager goes down, the cluster will lose the tie-breaking vote and will not be able to elect a leader4.

A better way to distribute the seven managers across three datacenters or availability zones is to use 3-2-2, which ensures that the cluster can tolerate the failure of any one datacenter or availability zone and still maintain the quorum. For example, if the datacenter with three managers goes down, the remaining four managers will have enough votes to form a quorum and elect a leader.Similarly, if the datacenter with two managers goes down, the remaining five managers will have enough votes to form a quorum and elect a leader4.Reference:

Swarm mode overview | Docker Docs

Administer and maintain a swarm of Docker Engines | Docker Docs

Raft consensus in swarm mode | Docker Docs

Docker Swarm: How to distribute managers across availability zones? - Stack Overflow


Question 3

Does this describe the role of Control Groups (cgroups) when used with a Docker container?

Solution: isolation between resources used by containers



Answer : A

Control Groups (cgroups) are a Linux kernel feature that allow you to limit, modify, or allocate resources as needed1.Docker uses cgroups to isolate the resources used by containers, such as CPU, memory, disk I/O, network, etc2.This means that each container can have its own set of resource limits and constraints, and that the containers cannot interfere with each other or with the host system2. This improves the security, performance, and reliability of the containers and the system as a whole.Reference:

Lab: Control Groups (cgroups) | dockerlabs

Docker run reference | Docker Docs


Question 4

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 run -- log driver=splunk for every container at run time



Answer : A

The commanddocker run --log-driver=splunkfor every container at run time will configure a Docker container to export container logs to the logging solution.The reason is that the--log-driveroption specifies the logging driver for the container, which determines how the container logs are handled1.Thesplunklogging driver is a plugin that sends container logs to HTTP Event Collector in Splunk Enterprise and Splunk Cloud2.To use thesplunklogging driver, you also need to provide some additional options with the--log-optflag, such as the Splunk token, URL, source, sourcetype, index, etc2. For example, to run a container with thesplunklogging driver and send the logs to a Splunk instance with the URLhttps://splunk.example.com:8088and the token176fabb6-7811-4b3a-8ba0-4d49302e50f2, you can use:

docker run --log-driver=splunk --log-opt splunk-token=176fabb6-7811-4b3a-8ba0-4d49302e50f2 --log-opt splunk-url=https://splunk.example.com:8088 ...

This way, you can configure a Docker container to export container logs to Splunk, which is a centralized logging solution.Alternatively, you can also configure thesplunklogging driver as the default logging driver for the Docker daemon by setting thelog-driverandlog-optskeys in thedaemon.jsonfile and restarting Docker3. This will apply thesplunklogging driver to all containers unless overridden by the--log-driveroption.Reference:

Configure logging drivers

Splunk logging driver

Set the logging driver for the Docker daemon


Question 5

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

Solution. Delete the image and remove permissions to the repository in the Docker

Trusted Registry.



Answer : B

= The sequence of steps will not completely delete an image from disk in the Docker Trusted Registry. Deleting the image and removing permissions to the repository will only remove the image from the registry's user interface and prevent unauthorized access to it.However, the image data will still remain on the registry's storage backend until garbage collection is performed1.Garbage collection is a process that removes unused blobs (layers) from the registry's storage2.To run garbage collection, the registry must be stopped and the commandbin/registry garbage-collect /etc/docker/registry/config.ymlmust be executed3.Alternatively, the registry can be configured to run garbage collection automatically at regular intervals4.Reference:

Deleting images | Docker Documentation

Garbage collection | Docker Documentation

How to delete images from a private docker registry? | Stack Overflow

Automating garbage collection | Docker Documentation


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Total 191 questions