Top 50+ Docker Interview Questions and Answers in 2021

By | October 9, 2021
Docker Interview Questions

Businesses want projects to be completed so that they can expand. With the demand for quicker and smoother methods, this notion has strengthened. As a result, modern and highly efficient tools to support business functions are in high demand. Docker is one such tool used to pack, ship, and run applications on containers.

Docker is an open-source containerization framework widely used for developing, installing, and executing software programs. Docker helps you to isolate the software from the infrastructure that supports it.

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Docker made its debut in the IT industry in 2013. Docker had over 8 billion container image downloads by the end of 2017. This has resulted in a major increase in the demand for Docker-trained professionals. As a result, applicants began searching for docker interview questions in order to maximize their work prospects. By 2020, the application container market is projected to hit $2.7 billion in size.

It pays to be prepared and ready for a job interview. Not only should you have your portfolio and references in order, but you ought to have a good understanding of the job and the business. Researching the company, for example, demonstrates to the interviewer that you are genuinely interested in the company and have taken the trouble to do your homework.

However, you can brush up on the particulars of the job you’re applying for. If you’re applying for a job that relies heavily on Docker, for example, you can brush up on your Docker skills.

We’ve compiled a curated list of Docker interview questions and answers for all expertise levels in the hopes of helping you prepare for that all-important job interview.

Although there’s no way to cover all of the Docker container interview topics accurately, you’ll find a decent representation of the problems you’ll most likely face. You’ll be more ready to cope down for the interview with a higher degree of trust once you’ve become more familiar with these Docker interview questions. Before we begin with the interview questions, let’s discuss why you should learn Docker.

Why should you learn Docker for a DevOps role?

There’s a lot more to application creation than just drafting code! They entail a lot of behind-the-scenes work, such as the use of various frameworks and technologies at different stages of their lifecycle, making the process more complicated and difficult.

Containerization’s design enables developers to simplify and easily accelerate application workflows while still enabling them to build using their chosen technologies and development environments. All of these elements are central to DevOps, making it all the more necessary for every developer to understand them in order to increase efficiency, speed up development, and keep application scalability and resource management in mind.

Consider containers as a pre-installed box with all of your application’s packages, dependencies, and applications, ready to be deployed to production with minimum modifications. Many businesses, such as PayPal, Uber, etc., use Docker to streamline operations and put infrastructure and protection closer together to create more stable applications.

Containers can be installed on a variety of systems, including bare metal, virtual machines, and the Kubernetes network, depending on the size or preferred platform. So, let’s begin with the simple questions and work on more difficult questions.

Top Docker Interview Questions and Answers

1. What do you understand by the term Docker?

Answer: Docker can be described as a containerization framework that bundles all of our applications into a single package, allowing us to run them in any environment. This means that our application can run smoothly in any environment, making it simple to build a product-ready app.

Docker bundles the appropriate software in a file system that includes all needed to run the code, including the runtime, libraries, and system resources. Containerization technology, such as Docker, uses the same OS kernel as the machine, making it very fast. This means we only need to run Docker once, and the rest of the process will be smooth and seamless because our OS is already running.

2. What do you understand by virtualization?

Answer: The process of creating a software-based, simulated version of something is known as virtualization. A single physical hardware device is used to build these simulated versions or environments. Virtualization allows you to divide a single system into several parts that function as separate, independent systems. This form of splitting is possible thanks to a program called Hypervisor. The Hypervisor’s environment is referred to as a Virtual Machine.

3. Name the latest version of Docker.

Answer: The latest version of Docker is 20.10.7, released on June 6, 2021.

4. What do you understand by containerization?

Answer: Because of dependencies, code built on one computer may not fit perfectly on another machine during the software development process. The containerization principle was used to solve this issue. So, an application is packaged and wrapped with all of its system settings and dependencies as it is built and deployed.

A container is a name for this package. When you want to run the program on a different device, you can use the container, which provides a bug-free environment because all the modules and dependencies are bundled together. Docker and Kubernetes are two of the most well-known containerization environments.

5. Explain hypervisors used in VMs in simple terms.

Answer: A hypervisor is a piece of software that enables virtualization. Virtual Machine Monitor is another name for it. It splits the host system into virtual environments and allocates resources to each one. On a single host system, you can essentially run multiple operating systems.

Hypervisors are divided into two categories. Type 1 hypervisors are also known as native hypervisors. It operates on the corresponding host device directly. It doesn’t need a base server operating system because it has immediate access to your host’s system hardware. The underlying host OS is used by the type 2 hypervisor. Hosted Hypervisor is another name for it.

6. Differentiate containerization and virtualization.

Answer: Containers build a separate environment in which the software can run. The software has exclusive use of the entire user area. Any modifications made inside the container have no effect on the server or other containers on the same host. Containers are an application layer abstraction. Each container represents a distinct application. In the case of virtualization, hypervisors provide the guest with an entire virtual machine, like Kernel. VMs are a hardware layer abstraction. Each virtual machine is a physical machine.

7. Explain Docker containers in simple terms.

Answer: It provides packaged, isolated, and contained environments to applications, including all of their dependencies, that run on the same OS kernel as the other containers. Each container is independent of the other, and they run in separate processes within the OS in userspace. Docker isn’t connected to any specific IT infrastructure, so it can run on any device or in the cloud.

We can create a Docker container from scratch using Docker images, build them, create containers associated with them, or use images from the Docker Hub. Let’s assume that Docker containers are only runtime instances of the environment’s template or Docker image to keep it easy.

8. Explain Docker Images in simpler terms.

Answer: Docker images are a template that contains the libraries, dependencies, config, and system files, etc., needed to create Docker containers. They contain several read-only layers of intermediate Images. You can download Docker images from registries such as Docker hub or create them from scratch. These Docker images are then used to create Docker containers by running the Docker run command of them, which creates additional writable layers on top of them that can be used to modify the images.

9. What do you understand by Docker hub?

Answer: Docker Hub can be thought of as a cloud registry that allows us to connect code repositories, create images, and test them. We can also save our built images locally or attach them to the Docker Cloud to deploy them to the host. We have a centralized resource discovery mechanism that we can use for team collaboration, process automation, delivery, and changing management by establishing a production pipeline.

The Docker hub contains tons of official and vendor-specific images that can be pulled by users onto their local machines and modify them or create containers associated with them. Some of the popular Docker images on Docker hub are ubuntu, alpine, centOS, MySQL, Nginx, etc.

10. Explain in simple terms the architecture of Docker.

Answer: The Docker Architecture is made up of three major components: a Docker Engine, which is a client-server framework. A server can be considered as a daemon operation, which in turn is a kind of long-running process. A REST API describes interfaces that applications can use to communicate with the daemon and send instructions. The CLI client uses the Docker REST API to monitor or interact with the Docker daemon via scripting or direct CLI commands. The underlying API and CLI are used by many other Docker applications.

11. Explain the uses of a Dockerfile in Docker.

Answer: A Dockerfile is a simple text file without any extension that a user can use to define instructions that would be executed while building an image. When we run the Docker build command, the daemon looks for the dockerfile inside the build context and starts executing the instructions inside it one by one.

Usually, the first instruction inside a dockerfile is the FROM instruction which is used to pull a base image, and each instruction after that adds a new intermediate image layer on top of the base image. It’s very important to understand the build cache mechanism that the build process uses to write the instructions in the best possible sequence.

Instructions should be written in such a way that the least frequently changing instruction comes to the top and the one which changes frequently comes at the bottom. This ensures that the build process can utilize the cache from the previous build to save time and resources.

12. Explain the Docker container life cycle.

Answer: Docker registries may be used to download Docker images. It may be a public Docker image or one of the many private Docker images that are downloadable. Anyone can pull a Docker Image on his own server by executing the Docker pull command.

Users may use the Docker create command to build a runtime instance called container after pulling the Docker Image. The newly formed container is now in the state called created. This indicates that the container has been produced but is not yet operational.

Users can start the container by running the docker start command on it after it has been created. The container will now be active on the host machine and will be in the started state.

Rather than using the start or create commands, you can use the docker run instruction on the images to launch the container and bring it to the running state.

You have three choices from this stage. The first is the state of being paused. You may use the docker pause command to pause all processes running within the docker container and then use the unpause command to restart them in the same state as before.

You may also use the docker stop command to stop the container completely, which will bring it to a halt. As a result, it goes into a stopped state. You may use the Docker start instruction to restart the container from scratch.

The final state is the dead state, which occurs when a container ceases to run and terminates despite the daemon’s best efforts due to some form of malfunction, such as a busy resource or system.

13. What do you understand by Docker Compose?

Answer: Docker Compose is a CLI tool that takes several containers and assembles them into applications that can be run on a single host using a specially formatted descriptor file. YAML files are used to configure the application’s services. The fact that it enables users to run commands on multiple containers simultaneously is unquestionably a plus.

This means that developers can create a YAML config script for their service and then start it with a single command. This tool, which was originally created for Linux, is now available for most OS, including Mac and windows.

One of Docker Composes key advantages is its extreme portability. Docker-compose up is sufficient to put up a complete development platform, which can then be taken down with docker-compose down. As a result, developers can easily centralize their application development and deploy their applications.

14. What do you understand by Docker Swarm?

Answer: It’s a Docker orchestration management platform that can be used for Docker applications. It primarily assists end users with the development and deployment of a Docker node cluster.

As a result, Docker Swarm provides the basic capabilities of managing and organizing multiple Docker containers in a Docker environment. Docker daemons are all the nodes in a Docker Swarm that communicate using the Docker API. The Docker Swarm containers can be deployed and managed from nodes in similar clusters.

In Docker, a swarm is a set of Docker hosts that are operating in the Docker Swarm mode. The hosts could act as workers who run the services or as managers who oversee member relationships. In some cases, a particular Docker host listed could act as both a manager and a worker.

Users may specify the desired state of a particular service during the development process. The service state requirements may include the service’s ports, the number of reproductions, and network and storage resources. Docker may also demonstrate productivity in maintaining the desired state by rescheduling or restarting unavailable tasks, as well as maintaining load balancing across several nodes.

15. Explain the functionalities of Docker Swarm.

Answer: It gives teams more functionality in terms of accessing and managing the environment. Docker Swarm mode allows for automatic load balancing in the Docker environment, as well as scripting for writing and structuring the Swarm environment. It also allows you to easily roll back environments to a previous save state.

Above all, it emphasizes high-security features. It improves connectivity between the Swarm’s worker and manager nodes while also increasing stability. It also highlights the advantages of increased scalability by the use of load balancing. Load balancing ensures that the Swarm environment is transformed into one that is more scalable.

Integrating Docker Swarm into the Docker Engine is one of the most relevant aspects. The Docker CLI’s direct integration with Docker Swarm eliminates the need for external orchestration software. For the development and handling of a swarm of Docker containers, you don’t need to use any other tool.

16. Explain the architecture of Docker Swarm.

Answer: Docker nodes are Docker Engine instances that are part of the Swarm. Users may choose to run one or several nodes on a single computer. General production deployments, on the other hand, rely on the span of Docker nodes across different physical devices. The base of the Docker swarm is made up of two types of nodes.

In Docker Swarm, the Manager Nodes are in charge of distributing and scheduling the incoming tasks to the Worker Nodes. They aid in orchestration and cluster management. In certain circumstances, Manager Nodes are also used to run services for Worker Nodes. The Manager Node’s overall cluster management tasks include cluster state maintenance and service schedule.

The Manager Node also can guarantee that the Swarm Mode is served efficiently to various HTTP API endpoints. The significance of the manager nodes becomes clear when multiple manager nodes are needed to maintain high availability. Furthermore, having multiple manager nodes allows for a faster recovery in the event of a manager system crash with no downtime. This is the primary explanation for Docker’s guidelines for introducing an odd number of nodes based on project availability requirements. A swarm can, in general, have up to 7 manager nodes, according to Docker.

Worker nodes are the second type of node in the Docker Swarm architecture. Since they are Docker Engine instances, worker nodes are close to manager nodes. The distinction between worker nodes and manager nodes is that worker nodes assist in the running of containers or services.

Worker nodes execute containers and resources according to the orders of manager nodes. The installation of an app to a swarm needs at least a manager node. As a consequence, by default, all manager nodes can be considered worker nodes. The availability must be set to ‘Drain’ to prevent the scheduler from putting tasks in a swarm on the manager node.

Understanding Docker Swarm’s design often involves utilities. In Docker, services are the definitions of tasks that can be performed on the nodes. In Docker Swarm, the service is the primary tool for users to communicate with the Swarm.

Users must define the container image to be used when constructing a service, as well as the commands to be executed within the running containers. Other options in the service, like CPU and memory limits, rolling upgrade policy, ports to be exposed, allowing a number of replicas of an image to be run in the Swarm, can all be defined by users.

Task scheduling is the final part of the design of Docker Swarm. A task is an important part of Docker Swarm because it ships a specific Docker container as well as the command that runs within it. In a swarm, the task is by far the most simple scheduling unit. Based on replicas identified in the service, the manager node delegates tasks to the worker nodes.

When a service is created or modified, the facilitator achieves the desired state by scheduling tasks. Every task is a slot that the scheduler fills by building a container for task instantiation. The orchestrator generates a new replica task to create a new container and repair the failing container in the event of a crash or malfunction in the health check of a container.

17. Explain the working of Docker Swarm.

Answer: The manager node in a dysfunctional cluster is aware of the state of the worker nodes. The manager node sends tasks to the worker nodes, which they accept. Agents on the worker nodes communicate to the manager node on the status of tasks on the node. As a consequence, the manager node can guarantee that the cluster’s desired state was maintained.

In Docker Swarm, any node in a similar cluster may deploy or receive services. During the service development process, users must decide the container image they would like to use. Users may create instructions and services for one of two scenarios: global or replicated. A global server could operate on all the nodes of the Swarm, while a replicated service’s manager node could assign tasks to worker nodes.

Although service in Docker Swarm is typically a definition of a state or task, the actual task defines the job to be completed. Docker could make it possible for a user to build services that can start tasks. Tasks assigned to a node, on the other hand, may not be delegated to other nodes.

A Docker Swarm environment may also become a container for several manager nodes, with only a single main manager node available for other manager nodes to choose from. The CLI is the foundation for creating a service. All resources can be coordinated using the API linked in the Swarm environment.

Task assignment allows users to assign jobs to tasks based on particular IP addresses. The dispatcher and scheduler are in charge of assigning tasks and guidelines to worker nodes in order to complete tasks. The worker node, therefore, communicates to the manager node to see if any new tasks have been assigned. Finally, in the Swarm environment, tasks allocated to the worker nodes are carried out.

18. Why should you use Docker?

Answer: Docker allows you to use the same versioning and packaging that platforms like Git and NPM offer for your server applications. Since Docker containers are just a single instance of Docker images, version tracking different builds of your container is a breeze. It’s also much easier to manage all of your dependencies because everything is contained.

With Docker, your build environment would be similar to your production environment. Also, there won’t be any dependency issues when running the same container on other machines.

You wouldn’t have to think about reconfiguring the server or reinstalling any of the dependencies if you were to connect another server to your cluster. You may share the container files with everyone after you’ve designed it, and they’ll be able to get your software running smoothly with just a few commands. With container orchestration or management platforms like Swarm and Kubernetes, Docker makes running multiple servers a breeze.

Docker also makes it possible to organize the code in preparation for deployment on new services. Let’s pretend you’re developing an application on a web server. You already have a lot of stuff built on that server: an Nginx web server for static content, a database for storing data on the backend, and possibly an Express.js API server. In a perfect world, you’d split these into separate systems that run on different servers, but creation can be messy.

You can bundle up your web server and simply run by creating an Nginx container, bundle up your API server and deploy it in a Node.js container, and run your database as its own container. You can run all three of these Docker containers on the same computer. It’s as simple as switching these containers to a new server if you need to move servers. You can switch one of those containers to a new server or allocate it across a cluster if you need to scale.

If you want to run different applications on a single VPS, Docker will help you save money. If each app has its own set of dependencies, the server will quickly become cluttered. Docker allows you to run several different containers on the same server without the process of one affecting the others or of the host.

19. What can you use Docker for?

Answer: Docker simplifies the development process by allowing developers to operate in structured environments by using local containers to deliver the software and services. CI/CD workflows benefit greatly from containers. Take the following scenario as an example. Your programmers run programs locally and use Docker containers to share them with their colleagues.

They use Docker to deploy their applications and run automated and manual tests in a test environment. Developers should correct bugs in the development environment before deploying on the test environment for further testing or validation. When the testing is done, it’s only a matter of pushing the modified Image to the manufacturing environment to bring the patch to the consumer.

The container-based Docker framework enables highly portable workflows. They can run on a developer’s desktop, in a data center on physical or virtual machines, on cloud providers, or in a hybrid environment.

Because of Docker’s portability and lightweight design, it’s also simple to dynamically handle workloads, scale them up or down in near real-time as business needs dictate. Docker is a compact and fast application.

It provides a better, cost-effective solution to hypervisor-based VMs, allowing you to make better use of your compute resources. Docker is ideal for high-density environments as well as medium and small deployments where more can be accomplished with fewer resources.

20. What is the Docker engine?

Answer: Docker Engine is a free containerization platform for developing and deploying applications. Docker Engine is a client-server program running on top of dockerd, a long-running daemon process. It includes APIs that define interfaces for software to communicate with and instruct the Docker daemon, as well as a CLI client docker.

Via scripting or direct Command-Line commands, the CLI uses Docker APIs to monitor or communicate with the Docker daemon. The underlying API and CLI are used by many other Docker applications. Docker objects such as images, volumes, etc., are generated and controlled by the daemon.

21. Explain namespaces in Docker.

Answer: A namespace is a Linux functionality that ensures the partitioning of OS resources is mutually exclusive. Namespaces provide a layer of separation between containers, which is the central principle behind containerization. The namespaces in Docker ensure that containers are portable and have no effect on the underlying host. PID, User, Mount, Network, etc., are examples of namespaces that Docker currently supports.

22. How can you scale containers in Docker?

Answer: Docker containers can indeed be scaled or expanded to any number of containers, from a few hundred to thousands or millions. The only stipulation is that the containers need memory and an operating system at all times, and these should not be limited as Docker scales. We can use Docker compose or swarm to manage the scaling of Docker containers.

23. Explain default networks in Docker.

Answer: Bridge network, host, and none are considered as the default networks in Docker. If no network is defined, the bridge network is the default one to which all the containers link. The server network aids in connecting to the host’s network stack. Without a network interface, the none network ensures access to a network stack that is specific to a container.

24. Can cloud overtake containers?

Answer: Docker containers are becoming more common, but Cloud providers are putting up a good fight. Docker, in my view, may never be overshadowed by the cloud. Using cloud computing in conjunction with containerization would undoubtedly raise the stakes. Organizations must understand their needs and dependencies and determine what is best for them. The majority of businesses have Docker incorporated with the cloud. They will be able to get the most out of both technologies in this manner.

25. Is it okay to execute stateful apps in Docker?

Answer: The idea behind stateful apps is that they collect their data on the local file system. If You need to choose to transfer the application to another machine, retrieving data becomes difficult. Hence, it’s better not to prefer running stateful apps on Docker.

26. Explain some features of Docker.

Answer: The features of Docker are –

  • Easy to create, run, and manage.
  • Allows version controlling.
  • Aids agile development.
  • Makes the application portable.
  • Allows scaling of applications.
  • Increases productivity of developers.

27. Give some downsides of Docker.

Answer: Some of the drawbacks of using Docker are –

  • There is no option for the storage of data.
  • Not up-to-the-mark option for monitoring of containers.
  • There is no auto-rescheduling of nodes that are not active.
  • Horizontal scaling is complicated.

28. Explain the memory-swap flag.

Answer: Memory-swap is a changed flag that has no effect unless memory is also set. When the container has used up all of the RAM available to it, swap allows it to assign express memory specifications to the disc.

29. Can you monitor Docker in production?

Answer: Docker has features, including docker stats or docker events, that can be used to track Docker in development. Docker stats display the container’s CPU and RAM consumption. Docker events include information on what’s going on inside the docker daemon.

30. Give some applications of Docker in real life.

Answer: The several areas where we can use Docker are –

  • Management of pipelines of codes.
  • To allow rapid deployment.
  • To create isolated environments for applications.
  • To aid developer productivity.
  • It gives multi-tenancy.
  • Has good debugging capabilities.
  • It simplifies configuration.

31. What are Docker objects?

Answer: There are several key components that are essential to run Docker. These are Docker objects and include containers, images, networks, volumes, services, swarm nodes, etc.

32. What’s the path of Docker volumes storage?

Answer: The default path where volumes are created is –

/var/lib/docker/volumes

33. How do Docker clients and daemon communicate?

Answer: They communicate with a combination of tools such as TCP, socket.IO, and Restful APIs.

34. How can you integrate CI/CD with Docker?

Answer: We can run Jenkins along with Docker, connect Docker to git repositories, and perform integration tests on several Docker containers using Docker compose.

35. How can you create Docker images?

Answer: There are two ways of creating Docker images. The first one is to pull directly from any Docker registry using the Docker pull command. We need to be logged in through the command line to do so. The second one is to create customized Docker images by specifying instructions inside a Dockerfile and then use the Docker build command to create the Image.

36. How can you control Docker using systemd?

Answer: We can use the following commands if we want to control Docker using the systemd.

$ systemctl start/stop docker
$ service docker start/stop

These commands help us to start and stop Docker services in our machines.

37. How can we use a JSON file for Docker compose instead of a YAML file?

Answer: To do so, we need to execute the following command.

$ docker-compose -f docker-compose.json up

38. What can you ensure persistent storage in Docker?

Answer: Once we exit or delete the container, the entire data is lost. However, if we still want access to any kind of data inside the Docker container, we can mount volumes to it. We can use a directory inside our local machine and mount it as a volume to a path inside the container. We can also simply create Docker volumes using the Docker volume create command. We can share a volume with multiple containers simultaneously.

39. How to access the bash of a Docker container?

Answer: To access the bash of a Docker container, we need to run the container in interactive mode. We can use the interactive and pseudo-TTY options to allow the terminal to let us input commands using a terminal driver. You can use the command below.

$ docker run -i -t <image-name> bash

40. What do you mean by CNM in Docker?

Answer: Container Networking Model (CNM) is a Docker, Inc. standard or specification that governs the networking of containers in a Docker environment. It provides provisions for multiple drivers for container networking.

41. Is IPv6 supported by Docker?

Answer: Docker does, in reality, support IPv6. Only Docker daemons running on Linux hosts support IPv6 networking. However, if you want the Docker daemon to support IPv6, you must edit/etc/docker/daemon.json file and change the ipv6 key to true.

42. How can you backup Docker Images?

Answer: To backup Docker images, we can either upload them onto a registry like Docker hub or convert them into a tarball archive file. We can upload a Docker image to a registry using the Docker push command below.

$ docker push <image-name>

To save the Docker image into an archived tarball file, we can use this command.

$ docker save -o <name-of-tar-file> <name-of-container>

43. How can you restore Docker Images?

Answer: If we have stored or backed up a Docker image into a registry, we can use the Docker pull command as mentioned below.

$ docker pull <image-name>

If we have saved the Docker image as a tarball file using the Docker save command, we can use the Docker load command to extract it back as an image in our local machine.

$ docker load -i <tarball-file-name>

44. When can we not remove a container?

Answer: It is not possible to remove a container if it is paused or running. The container needs to be stopped before we can kill or remove it.

45. Differentiate between Docker ADD and COPY instructions.

Answer: The Docker ADD command is used to copy files and directories from the local machine to the containers. It can copy files from a directory, a URL, Git, bitbucket, or even an archived file. If we specify the source directory as an archive file, it will extract it and then load it to the container.

The Docker COPY command also copies files to the container. However, it only copies from directories and does not support copying from URLs. If we specify an archived file, it will copy it as it is without extracting it.

46. Explain the difference between Docker start and run commands.

Answer: The Docker start command is used to simply start a container without running it. It simply creates an instance of the Image and maintains the container in the start state. However, the Docker run command is used to run a container and keeps it in a running state. When the container is running, we can execute commands inside it or access its file system.

47. How can we run commands inside Docker containers?

Answer: There are multiple ways to run commands inside Docker containers. We can use a Dockerfile and use the RUN instruction along with a command that we want to run inside the Docker container. We can also use the Docker run command to start the Docker container and access the bash of the container. Inside the bash, we can directly run commands. If the container is running in the background or detached mode, we can use the Docker exec command to run commands inside that container.

48. How can you remove a running container or Image?

Answer: We can remove a running container or Image using the force option along with the container or Image remove command. We can use the below commands.

$ docker rm -f <container-name>
$ docker rmi -f <image-name>

49. How can we identify the status of a container?

Answer: We can use the Docker container list or ps commands to do so.

To display all the running containers, we can use –

$ docker ps

To display all the containers in the machine, we can use –

$ Docker ps -a

Or

$ docker container ls -a

50. What is a build cache?

Answer: When we create Docker images using Dockerfiles, we specify instructions inside it. Each instruction creates a new intermediate image layer. When we first build the Image, it executes all the instructions one by one. When we try to build it once again after making any changes, it uses the cache from the previous build for all unchanged instructions, and as soon as it encounters a changed instruction, the cache is broken for this, and all subsequent instructions and executes these instructions freshly.

51. What are the two types of registries?

Answer: There are two types of Docker registries – private and public. Private registries can be in a local machine or hosted on a cloud, and only you can have access to it. Public registries are those from which any authenticated user can pull images from. Dockerhub supports both of these kinds.

Wrapping Up!

DevOps techniques are exploding in popularity. Because of the need to build software faster and manage it better as systems become more distributed, programmers have switched to containerization. They also make continuous integration and implementation simpler and quicker, which is why these innovations have exploded in popularity.

Docker is the most well-known and widely used platform for containerization, continuous integration/development, and continuous deployment, thanks to its excellent pipeline support. With the growing community, Docker has been demonstrated to be useful for a variety of use cases, which makes learning it even more exciting!

Faster device scaling, smoother software distribution, and adjusting to emerging technology, to name a few things, held them in the game. That’s when Docker entered the frame, improving these companies’ chances of winning the race. Companies have understood the value of adapting to and taking advantage of evolving market dynamics as industry competition has increased.

This ends our discussion of Docker Interview Questions. We hope that this guide will help you to ace your Docker interviews with flying colors.

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