DCA Dumps with Practice Exam Questions Answers
DCA by Docker Certified Associate Actual Free Exam Practice Test
The DCA certification is an internationally recognized credential that demonstrates an individual's proficiency in Docker technology. It is a valuable certification for developers, system administrators, and IT professionals who want to enhance their skills in containerization and Docker technology. The DCA certification validates the candidate's ability to design, build, deploy, and manage Docker containers and applications.
Docker Certified Associate (DCA) exam is a certification program that validates the skills and knowledge of professionals who use Docker technologies. It is an industry-recognized certification that demonstrates a candidate's ability to work with Docker environments and understand the underlying concepts of containerization. The DCA exam covers a wide range of topics, and candidates who pass the exam are able to demonstrate their proficiency in all these areas.
NEW QUESTION # 69
Which of the following commands starts a Redis container and configures it to always restart unless it is
explicitly stopped or Docker is restarted?
- A. 'docker run -d --failure omit-stopped redis'
- B. 'docker run -d --restart omit-stopped redis'
- C. 'docker run -d --restart-policy unless-stopped redis'
- D. 'docker run -d --restart unless-stopped redis'
Answer: D
NEW QUESTION # 70
A Kubernetes node is allocated a /26 CIDR block (64 unique IPs) for its address space.
If every pod on this node has exactly two containers in it, how many pods can this address space support on this node?
- A. 0
- B. 64 for every service routing to pods on this node
- C. 32 in every Kubernetes namespace
- D. 1
- E. 2
Answer: D
Explanation:
Explanation
A Kubernetes node is allocated a /26 CIDR block (64 unique IPs) for its address space. This means that the node can assign up to 64 IP addresses to its resources, such as pods and containers. If every pod on this node has exactly two containers in it, then each pod will need two IP addresses, one for each container. Therefore, the node can support up to 32 pods, since 64 / 2 = 32. The other options are incorrect because they either exceed the available IP addresses or do not account for the number of containers per pod. References:
*CIDR Blocks and Container Engine for Kubernetes - Oracle
*How kubernetes assigns podCIDR for nodes? - Stack Overflow
NEW QUESTION # 71
Will a DTR security scan detect this?
Solution. private keys copied to the image
- A. Yes
- B. No
Answer: B
Explanation:
Explanation
A DTR security scan does not detect private keys copied to the image. A DTR security scan is a feature that scans images for known vulnerabilities in the software packages or dependencies that are installed in the image. A DTR security scan does not check for private keys or other sensitive data that may be accidentally or intentionally copied to the image. To avoid copying private keys to the image, you should use Docker secrets or other secure mechanisms to manage your credentials. References:
https://docs.docker.com/ee/dtr/user/manage-images/scan-images-for-vulnerabilities/,
https://docs.docker.com/engine/swarm/secrets/
NEW QUESTION # 72
Does this describe the role of Control Groups (cgroups) when used with a Docker container?
Solution: accounting and limiting of resources
- A. No
- B. Yes
Answer: B
Explanation:
Explanation
= Control Groups (cgroups) are a feature of the Linux kernel that allow you to limit the access processes and containers have to system resources such as CPU, memory, disk I/O, network, and so on1. Control groups allow Docker Engine to share available hardware resources to containers and optionally enforce limits and constraints2. For example, you can use the docker run command to specify the CPU shares, memory limit, or network bandwidth for a container3. By using cgroups, you can ensure that each container gets the resources it needs and prevent resource starvation or overcommitment4. References:
* Lab: Control Groups (cgroups) | dockerlabs
* Runtime metrics | Docker Docs
* Docker run reference | Docker Docs
* Docker resource management via Cgroups and systemd
NEW QUESTION # 73
You want to create a container that is reachable from its host's network.
Does this action accomplish this?
Solution.Use network connect to access the container on the bridge network.
- A. Yes
- B. No
Answer: B
Explanation:
Explanation
= Using network connect to access the container on the bridge network does not accomplish creating a container that is reachable from its host's network. The network connect command connects a container to an existing network, but it does not expose the container's ports to the host1. The bridge network is the default network that Docker creates for containers, and it provides isolation from the host network2. To create a container that is reachable from its host's network, you need to use the host network driver, which disables network isolation and uses the host's network stack directly3. Alternatively, you can use the port mapping feature to publish specific ports of the container to the host4. References:
* docker network connect | Docker Docs
* Bridge network driver | Docker Docs
* Host network driver | Docker Docs
* Publish ports on the host | Docker Docs
NEW QUESTION # 74
Is this a way to configure the Docker engine to use a registry without a trusted TLS certificate?
Solution: Pass the '--insecure-registry' flag to the daemon at run time.
- A. No
- B. Yes
Answer: B
Explanation:
Explanation
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NEW QUESTION # 75
Does this command create a swarm service that only listens on port 53 using the UDP protocol?
Solution. 'docker service create -name dns-cache -p 53:53 -constraint networking.protocol.udp=true dns-cache"
- A. Yes
- B. No
Answer: B
Explanation:
The command docker service create -name dns-cache -p 53:53 -constraint networking.protocol.udp=true dns-cache will not create a swarm service that only listens on port 53 using the UDP protocol. This command has several syntax errors and invalid options. The correct syntax for creating a swarm service is docker service create [OPTIONS] IMAGE [COMMAND] [ARG...]1. The correct options for specifying the service name, port mapping, and network mode are --name, --publish, and --network respectively1. The option -constraint is not a valid option for the docker service create command. To create a swarm service that only listens on port
53 using the UDP protocol, you need to use the --publish option with
the protocol=udp and mode=host parameters, and the --network option with the host value23. For example, the following command creates a global service using host mode and bypassing the routing mesh2:
docker service create --name dns-cache \
--publish published=53,target=53,protocol=udp,mode=host \
--mode global \
--network host \
dns-cache
References:
* 1: docker service create | Docker Docs
* 2: Use swarm mode routing mesh | Docker Docs
* 3: Manage swarm service networks | Docker Docs
NEW QUESTION # 76
Which of the following is supported by control groups?
- A. Limit CPU usage within a container
- B. Collect net
- C. Manage certificates
- D. Isolate processes in a container
Answer: A
NEW QUESTION # 77
Is this a Linux kernel namespace that is disabled by default and must be enabled at Docker engine runtime to be used?
Solution: net
- A. Yes
- B. No
Answer: B
Explanation:
Explanation
net is not a Linux kernel namespace that is disabled by default and must be enabled at Docker engine runtime to be used. According to the official documentation, net is one of the namespaces that are enabled by default when using namespaces for isolation.
References: https://docs.docker.com/engine/security/userns-remap/#user-namespace-known-limitations
NEW QUESTION # 78
The Kubernetes yaml shown below describes a networkPolicy.
Will the networkPolicy BLOCK this traffic?
Solution: a request issued from a pod lacking the tier: api label, to a pod bearing the tier: backend label
- A. No
- B. Yes
Answer: B
Explanation:
The networkPolicy shown in the image is designed to block traffic from pods lacking the tier: api label, to pods bearing the tier: backend label. This is because the policy is set to matchLabels: tier: backend, and the ingress is set to - from: podSelector: matchLabels: tier: api. Therefore, any traffic that does not match these labels will be blocked.
References:
* Isolate containers with a user namespace | Docker Docs
* The mnt namespace - Docker Cookbook - Second Edition
* Container security fundamentals part 2: Isolation & namespaces
I hope this helps you understand the concept of networkPolicy and how it works with Kubernetes. If you have any other questions related to Docker, please feel free to ask me.
NEW QUESTION # 79
Will this action upgrade Docker Engine CE to Docker Engine EE?
Solution. Disable the Docker service via 'chkconfig' or 'systemctl'.
- A. Yes
- B. No
Answer: B
Explanation:
Explanation
Disabling the Docker service via chkconfig or systemctl does not upgrade Docker Engine CE to Docker Engine EE. Disabling the Docker service only stops and prevents Docker from starting automatically on system boot. It does not change or upgrade the version of Docker Engine installed on the system. To upgrade Docker Engine CE to Docker Engine EE, you need to uninstall Docker Engine CE and install Docker Engine EE following the official instructions for your operating system. References:
https://docs.docker.com/engine/install/linux-postinstall/#disable-docker-from-starting-automatically-on-boot,
https://docs.docker.com/engine/install/centos/#uninstall-old-versions,
https://docs.docker.com/engine/install/ubuntu/#uninstall-old-versions,
https://docs.docker.com/engine/install/debian/#uninstall-old-versions,
https://docs.docker.com/ee/docker-ee/linux-install/
NEW QUESTION # 80
You are running only Kubernetes workloads on a worker node that requires maintenance, such as installing patches or an OS upgrade
Which command must be run on the node to gracefully terminate all pods on the node, while marking the node as unschedulable?
- A. 'kubectl cordon <node name>'
- B. 'docker node update --availability drain <node name>'
- C. 'docker swarm leave'
- D. 'kubectl drain <node name>'
Answer: A
NEW QUESTION # 81
Does this describe the role of Control Groups (cgroups) when used with a Docker container?
Solution: isolation between resources used by containers
- A. No
- B. Yes
Answer: B
Explanation:
Explanation
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. References:
* Lab: Control Groups (cgroups) | dockerlabs
* Docker run reference | Docker Docs
NEW QUESTION # 82
Will this action upgrade Docker Engine CE to Docker Engine EE?
Solution. Disable the Docker service via 'chkconfig' or 'systemctl'.
- A. Yes
- B. No
Answer: B
Explanation:
The action will not upgrade Docker Engine CE to Docker Engine EE. Disabling the Docker service via chkconfig or systemctl will only stop the Docker daemon from running, but it will not change the version or edition of the Docker engine1. To upgrade Docker Engine CE to Docker Engine EE, you need to follow these steps2:
* Download your Docker Enterprise license from the Docker Store).
* Install the docker-ee package from the Docker repository.
* Restart the Docker service and verify the version and edition. References: Start or stop the Docker daemon), How to upgrade Docker 18.09 Community Edition to Docker Enterprise 18.09)
NEW QUESTION # 83
What is one way of directly transferring a Docker Image from one Docker host in another?
- A. 'docker save' the image to save it as TAR file and copy it over to the target host. Then use 'docker load' to un-TAR the image back as a Docker image.
- B. 'docker commit' to save the image outside of the Docker filesystem. Then transfer the file over to the target host and 'docker start' to start the container again.
- C. 'docker push' the image to the IP address of the target host.
- D. There is no way of directly transferring Docker images between hosts. A Docker Registry must be used ad an intermediary.
Answer: A
NEW QUESTION # 84
Seven managers are in a swarm cluster.
Is this how should they be distributed across three datacenters or availability zones?
Solution: 5-1-1
- A. Yes
- B. No
Answer: B
Explanation:
= 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. References: You can find some useful references for this question in the following links:
* Docker Swarm overview
* Swarm mode key concepts
* Swarm mode best practices
NEW QUESTION # 85
Will this configuration achieve fault tolerance for managers in a swarm?
Solution: only two managers, one active and one passive.
- A. Yes
- B. No
Answer: B
Explanation:
Explanation
This configuration will not achieve fault tolerance for managers in a swarm, because having only two managers creates a risk of losing quorum if one manager fails or becomes unavailable. According to the official documentation, having two managers also does not provide any benefits over having one manager, since both managers must be available for any management operations.
References: https://docs.docker.com/engine/swarm/admin_guide/#add-manager-nodes-for-fault-tolerance
NEW QUESTION # 86
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 <eontainer-id>
- A. Yes
- B. No
Answer: B
Explanation:
Explanation
= The command docker logs <container-id> will not configure a Docker container to export container logs to the logging solution. This command is used to fetch the logs of a container from the Docker daemon, not to send them to an external service1. To export container logs to a logging solution, such as Splunk, you need to use a Docker logging driver2. A logging driver is a way of plugging into the Docker engine to forward logs to a specific destination2. Docker supports several built-in logging drivers, including one for Splunk3. To use the Splunk logging driver, you need to specify the --log-driver splunk option when running a container, and provide some additional options, such as the Splunk HTTP Event Collector token and URL3. Alternatively, you can configure the Splunk logging driver as the default logging driver for the Docker daemon by editing the daemon.json file4. References:
* 1: docker logs | Docker Docs
* 2: Configure logging drivers | Docker Docs
* 3: Splunk logging driver | Docker Docs
* 4: Collecting docker logs and stats with Splunk | Splunk
NEW QUESTION # 87
Which set of commands can identify the publishd port(s) for a container? (Choose 1.)
- A. 'docker port inspect', 'docker container inspect'
- B. 'docker info','docker network inspect'
- C. 'docker container inspect', docker port'
- D. 'docker network inspect','docker port'
Answer: C
NEW QUESTION # 88
What is the difference between a resource limit and a resource reservation when scheduling services?
- A. A resource limit is used to find a host with adequate resources for scheduling a hard limit for your service, while a reservation is hard limit for your service.
- B. A resource limit and a resource reservation can be used interchangeably.
- C. A resource limit is hard limit for your service, while a reservation is used to find a host with adequate resources for scheduling. Correct
- D. A resource limit is a soft limit for your service, while a reservation is hard limit and the docker engine will do its best to keep your service at the limit.
Answer: B
NEW QUESTION # 89
In Docker Trusted Registry, is this how a user can prevent an image, such as 'nginx:latest', from being overwritten by another user with push access to the repository?
Solution: Use the DTR web Ul to make all tags in the repository immutable.
- A. Yes
- B. No
Answer: B
Explanation:
Explanation
This is not how a user can prevent an image from being overwritten by another user with push access to the repository, because making all tags in the repository immutable will also prevent the user from updating their own image tags. According to the official documentation, a better way to prevent an image from being overwritten is to use promotion policies that only allow certain users or teams to push images with specific tags.
References: https://docs.docker.com/ee/dtr/user/promotion-policies/overview/
NEW QUESTION # 90
Which networking drivers allow you to enable multi-host network connectivity between containers?
- A. bridge, macvlan, ipvlan, overlay
- B. host, macvlan, overlay, user-defined
- C. macvlan, ipvlan, and overlay
- D. bridge, user-defined, host
Answer: A
Explanation:
The networking drivers that allow you to enable multi-host network connectivity between containers are bridge, macvlan, ipvlan, and overlay. These drivers create networks that can span multiple Docker hosts, and therefore enable containers on different hosts to communicate with each other. The other drivers, such as host, user-defined, and none, create networks that are either isolated or limited to a single host. Here is a brief overview of each driver and how it supports multi-host networking:
*bridge: The bridge driver creates a network that connects containers on the same host using a Linux bridge.
However, it can also be used to create a network that connects containers across multiple hosts using an external key-value store, such as Consul, Etcd, or ZooKeeper. This feature is deprecated and not recommended, as it requires manual configuration and has some limitations. The preferred driver for multi-host networking is overlay1.
*macvlan: The macvlan driver creates a network that assigns a MAC address to each container, making it appear as a physical device on the network. This allows the containers to communicate with other devices on the same network, regardless of the host they are running on. The macvlan driver can also use 802.1q trunking to create sub-interfaces and isolate traffic between different networks2.
*ipvlan: The ipvlan driver creates a network that assigns an IP address to each container, making it appear as a logical device on the network. This allows the containers to communicate with other devices on the same network, regardless of the host they are running on. The ipvlan driver can also use different modes, such as l2, l3, or l3s, to control the routing and isolation of traffic between different networks3.
*overlay: The overlay driver creates a network that connects multiple Docker daemons together using VXLAN tunnels. This allows the containers to communicate across different hosts, even if they are on different networks. The overlay driver also supports encryption, load balancing, and service discovery. The overlay driver is the default and recommended driver for multi-host networking, especially for Swarm services4.
References:
*Use bridge networks
*Use macvlan networks
*Use ipvlan networks
*Use overlay networks
NEW QUESTION # 91
Does this command display all the pods in the cluster that are labeled as env; development'?
Solution. 'kubectl gel pods --all-namespaces -I 'env in (development)''
- A. No
- B. Yes
Answer: B
Explanation:
Explanation
This command does display all the pods in the cluster that are labeled as env: development. The kubectl get pods command shows information about all the pods in a cluster or a specific namespace. The
--all-namespaces flag tells kubectl to include pods from all namespaces in the output. The -l flag tells kubectl to filter the output by a label selector, which is an expression that matches labels to values. The label selector
'env in (development)' matches pods that have a label env with a value development. Therefore, this command displays all the pods in the cluster that are labeled as env: development. References:
https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#get,
https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#label-selectors
NEW QUESTION # 92
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