Docker Certified Associate Interview Questions

Preparing for an interview is as important as preparing for an exam. Therefore, preparing for an interview takes a lot more practice and confidence to ace any exam. You have to make the best first impression. So to help our candidates to prepare well for the Docker Certified Associate interview, we have tried our best to present you with the best and expert-revised interview questions. Candidates should research the company, job roles, and responsibilities, and most importantly look confident while answering any question. Moreover, we have covered all interview questions from basic to intermediate and to advance level. Therefore, we highly recommend the aspirants prepare with the best and achieve the best. But first, you should be familiar with the basics of what the Docker Certified Associate exam is all about.

Overview

In today’s modern era of technology, Docker skills are highly sought after, and in demand. Therefore, the Docker Certified Associate (DCA) exam is specially formulated with all the skillsets designed by experienced Docker practitioners. After completion of the certification, the candidates will set themselves apart as uniquely qualified to run company workloads at scale with Docker Enterprise Edition.

Now, let’s begin with some Docker Certified Associate Interview Questions.

1. Explain the docker service scale?

The scale command enables the user to scale one or more replicated services either up or down to the desired number of replicas. This command cannot be applied to services that are global mode.

2. What is the use of docker service scale?

The docker service scale command allows you to set the desired number of tasks for multiple services at once.

3. List some default Network drivers?

Some of the default Network drivers are as follow:

Bridge
Host
Overlay
Macvlan
Lastly, network plugins

4. How Host networks proves to be useful?

Host networks are best when the network stack should not be isolated from the Docker host, but you want other aspects of the container to be isolated. Therefore, they can be used for the same.

5. Explain bridge networks in terms of networking?

In terms of networking, a bridge network is a Link Layer device that forwards traffic between network segments. A bridge can be a hardware device or a software device running within a host machine’s kernel.

6. Explain bridge networks in terms of Docker?

In terms of Docker, a bridge network uses a software bridge that allows containers connected to the same bridge network to communicate, while providing privacy from containers that are not connected to that bridge network.

7. List the advantages of using user-defined bridges over the default bridge?

Firstly, User-defined bridges provide automatic DNS resolution between containers.
Secondly, User-defined bridges provide better isolation.
Thirdly, Containers can be attached and detached from user-defined networks on the fly.
Fourthly, Each user-defined network creates a configurable bridge.
Lastly, Linked containers on the default bridge network share environment variables.

8. How can you share environment variables between two containers?

Multiple containers can mount a file or directory containing the shared information, using a Docker volume.
Multiple containers can be started together using docker-compose and the compose file can define the shared variables.
Lastly, you can use swarm services instead of standalone containers and take advantage of shared secrets and configs.

9. How to disconnect a container from a user-defined bridge?

If you want to disconnect a running container from a user-defined bridge, use the docker network disconnect command.

10. What are overlay networks?

The overlay network driver creates a distributed network amongst multiple Docker daemon hosts. This network sits on top of the host-specific networks, allowing containers connected to it to communicate securely when encryption is approved.

11. When you initialize a swarm or join a Docker host to an existing swarm, two new networks are created on that Docker host. Name them?

an overlay network called ingress.
Lastly, a bridge network called docker gwbridge.

12. What do you understand by ingress?

Ingress handles the control and data traffic related to swarm services. Whenever you create a swarm service and do not connect it to a user-defined overlay network, it connects to the ingress network by default.

13. What is the use of gwbridge?

Gwbridge connects the individual Docker daemon to the other daemons participating in the swarm.

14. List the advantages of Volumes over bind mounts?

Volumes are more comfortable to back up or migrate than bind mounts.
You can handle volumes using Docker CLI commands or the Docker API.
Volumes work on both Linux and Windows containers.
Volumes can be more safely shared among multiple containers.
Volume drivers let you store volumes on remote hosts or cloud providers, encrypt the contents of volumes, or add other functionality.
New volumes can have their content pre-populated by a container.
Lastly, Volumes on Docker Desktop have much higher performance than bind mounts from Mac and Windows hosts.

15. Why are Volumes better than persisting data?

Volumes are often a better choice than persisting data in a container’s writable layer, because a volume does not increase the size of the containers practicing it, and the volume’s contents exist outside the lifecycle of a given container.

16. How to share data among machines?

There are several ways to Share data among machines when developing your applications. One is to add logic to your application to store files on a cloud object storage system like Amazon S3. Another is to create volumes with a driver that supports writing files to an external storage system like NFS or Amazon S3.

17. List the different types of volumes?

Named volumes have a specific source from outside the container.
Lastly, Anonymous volumes have no specific source so when the container is deleted, instruct the Docker Engine daemon to remove them

18. What are the different types of service deployments?

Firstly, replicated
Lastly, global.

19. Explain global services?

Global service is a service that works one task on every node. There is no pre-specified number of tasks. Moreover, each time you add a node to the swarm, the orchestrator creates a task and the scheduler assigns the task to the new node.

20. Who are the good candidates for global services?

Good candidates for global services are:

monitoring agents
an anti-virus scanners or other types of containers that you want to run on every node in the swarm.

21. List the different types of mounts supported by Docker?

Docker supports three different kinds of mounts. They are:

Bind mount
Named mount
Lastly, tmpfs mounts

22. What is a Bind mount?

A bind mount makes a file or directory on the host available to the container it is mounted within. A bind mount may be either read-only or read-write. Moreover, while using bind mounts and your host and containers have various concepts of permissions, access controls, or other such details, you will run into portability issues.

23. Describe Named volumes?

A named volume is a mechanism for decoupling persistent data needed by your container from the image used to create the container and from the host machine.

24. What is bind propagation?

Bind propagation refers to whether or not mounts created within a given bind mount or named volume can be propagated to replicas of that mount.

25. What do you understand by Container networking?

The container network is transparent from within the container. It has a network interface with an IP address, a gateway, a routing table, DNS services, and other networking details.

26. What is a Dockerfile?

A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image. Moreover, Docker can build images automatically by reading the instructions from a Dockerfile .

27. List the applications of BuildKit?

Firstly, it detect and skip executing unused build stages
Parallelize building independent build stages
Incrementally transfer only the changed files in your build context between builds
Detect and skip transferring unused files in your build context
Use external Dockerfile implementations with many new features
Avoid side-effects with the rest of the API
Lastly, it prioritize your build cache for automatic pruning

28. The Custom Dockerfile implementations allows you to?

Automatically get bugfixes without updating the Docker daemon
Make sure all users are using the same implementation to build your Dockerfile
Use the latest features without updating the Docker daemon

29.What does a Troubleshoot page contains?

The Troubleshoot page contains the following options:

Restart Docker Desktop
Support
Reset Kubernetes cluster
Clean / Purge data
Lastly, Reset to factory default

30. What are the four major areas to consider when reviewing Docker security?

Firstly, the intrinsic security of the kernel and its support for namespaces and cgroups
The attack surface of the Docker daemon itself
loopholes in the container configuration profile, either by default, or when customized by users.
Lastly, the hardening security features of the kernel and how they interact with containers.

31. What are Control groups?

Control Groups are another key component of Linux Containers. They complete resource accounting and limiting. Moreover, they provide many useful metrics, but they also help ensure that each container gets its fair share of memory, CPU, and more importantly, that a single container cannot bring the system down by consuming one of those resources.

32. What is Docker Content Trust (DCT)?

Docker Content Trust (DCT) provides the capability 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.

33. List the different types of Key sets?

Firstly, an offline key that is the root of DCT for an image tag
Secondly, repository or tagging keys that sign tags
Lastly, server-managed keys such as the timestamp key, which provides freshness security guarantees for your repository.

34. List the commands that operate with DCT?

Push
Build
Create
Pull
Lastly, run.

35. How PKI makes it simple to securely deploy a container orchestration system?

The swarm mode public key infrastructure (PKI) system built into Docker makes it easy to securely deploy a container orchestration system. The nodes in a swarm use mutual Transport Layer Security (TLS) to authenticate, authorize, and encrypt the communications with other nodes in the swarm.

36. What is the use of Storage drivers?

Docker maintains numerous storage drivers, using a pluggable architecture. The storage driver controls whereby images and containers are stored and managed on your Docker host.

37. List the different types of files which can be put in the plugin directory?

.sock
.spec
.json

38. Define Orchestration?

Tools that are used to manage, scale, and maintain containerized applications are called orchestrators, and the most common examples of these are Kubernetes and Docker Swarm.

39. What are Kubernetes?

The arranged applications managed by an orchestrator are called Kubernetes. Kubernetes provides many tools for scaling, networking, securing, and maintaining your containerized applications.

40. What are Pods?

All containers in Kubernetes are scheduled as pods, which are groups of co-located containers that share some resources.