Best Docker Interview Question and Answers

Orange Technomind 27-Sep-2019
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Best Docker Interview Questions and Answers

Docker Interview Questions and answers for beginners and experts level.Here are the list of frequently asked Docker Interview Questions with answers by Orange TechnoMind. We hope these Docker Interview Questions and answers which will help you to get place in the top notch companies.A Docker course can be considered a wise decision that can help shape up the career and provide the stepping stone towards a career full of new opportunities.If you are looking for best Docker Training in UK then you are at right place to learn.This Docker training is also helpful in upgrading your skill. 

 

What is Docker?

Docker is a platform to run every software isolated and securely.Internally it achieves it with the aid of using kernel containerization function

 

What is Docker Container?

Docker Container is the instantiation of docker image. In other words, it is the run time instance of images. Images are set of files whereas containers run the image inside isolated

 

What are the networks that are available by default?

bridge - It is the default network all containers connect to in case you don’t specify the network yourself

none - connects to a container unique network stack that lacks a network interface

host  - connects to the host’s network stack there could be no isolation between the host machine and the container, as a ways as network is involved

 

What is Docker hub?

Docker hub is the most important public repository of the image containers that is being maintained by the community of developers and individual members.

 

What's the advantage of Docker over hypervisors?

Docker is light weight and more efficient in terms of resource uses as it uses the host underlying kernel instead of developing its very own hypervisor.

 

Difference between Docker Image and container?

Docker containers are built from docker image. A Docker image does not have a state and its state in no way changes as it is just set of documents while Docker container has its execution state.

 

How do you create Docker images?

Uisng Docker file Docker images are created . Docker build is the command and important features of Docker engine to create Docker image out of Docker fileOnce an image has been created, as many containers are required may be spawned.

 

How is a Docker container created? 

We are able to create Docker container by running this command

docker run -t -i

 


 

 

Difference between Docker and VM (Virtual Machine)?

 

 

Virtual Machines   

Docker Containers

Need more resources   

Less resources are used

Process isolation is done at hardware level   

 

Process Isolation is done at Operating System level

 

Separate Operating System for each VM   

 

Operating System resources can be shared within Docker

 

VMs can be customized

Custom container setup is easy

Creation of VM takes time

Creation of docker is very quick

Booting takes minutes   

Booting is done within seconds

 

Give an explanation about  components of Docker architecture ?

The Docker works on client-server architecture. The Docker client establishes communication and interacts with the Docker Daemon. The Docker client and Daemon can run at the identical machine. A Docket client can also be connected to a remote Docker Daemon. The different sorts of Docker components in a Docker structure are–

Docker client: This performs Docker build pull and run operations to set up communication with the Docker Host. The Docker command makes use of Docker API to call the queries to be run.

Docker Host: This component consists of Docker Daemon, containers and its images. The images can be the kind of metadata for the applications which are containerized in the containers. The Docker Daemon establishes a connection with Registry.

Registry: This component could be storing the Docker images. the public registries are Docker Hub and Docker Cloud which can be s utilized by anybody.

 

What are Docker image and Docker Hub?

The Docker image is a set of documents and an aggregate of parameters in order to permit developing the instances to run in separate containers as an isolated manner. The Docker hub is a type of repository to the images where these images can be stored and this access is public. The Docker run command may be used to create the instance known as container which can be run using the Docker image. Docker hub is the most important public repository of the image containers that is being maintained through the network of developers and individual contributors.

 

What are the special functionalities and applications of using Docker?

The special functionalities and applications of the usage of and enforcing Docker are as under:

  • It simplifies the configuration and gives ease at infrastructure level configuration.
  • It manages the code pipeline without difficulty which affords constant environment and stability in the application.
  • It enables the isolation of the utility.
  • It improves the productiveness of the developer by way of permitting the developer to totally concentrate on business logic.
  • It permits quite a few debugging capabilities that gives severe useful functionalities to implement.
  • It permits rapid deployment within the shape of virtualization on the operating system level.
  • It reduces the utilization of a couple of servers within the form of containerization.

 

What's a Docker Registry?

A Docker Registry is a place where all of the Docker images could be saved and Docker Cloud and Docker Hub are the public registries where those images can be hosted upon. The Docker hub is the cloud-based repository for the Docker images. An very own registry also can be set up as in step with the requirement. Docker Data Center (DDC) can also be used which incorporates DTR (Docker Trusted Registry). Docker save will provide the characteristic of buying and promoting the Docker images.
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What's the lifecycle of Docker container?

The life cycle of the Docker containers as underneath:

  • Create a container.
  • Run the Docker container.
  • Pause the Container.
  • Unpause the Container.
  • Start the Container.
  • Stop the Container.
  • Restart the Container.
  • Kill the Container.
  • Destroy the Container.

 

What are Docker Namespaces?

The Namespaces in Docker is a technology which offers remote workspaces called the container. For the Docker containers it provide a layer of isolation.

 

What’s the difference between up, run, and start?

docker-compose-up comand is used to begin or restart all the services defined in a docker-compose.yml. inside thedefault “attached” mode, you’ll see all of the logs from all of the containers. In “detached” mode (-d), Compose exits after starting the containershowever the containers keep to run inside the background.

docker-compose-run command is for running “one-off” or “ad-hoc” tasks. It requires the service name you need to run and handiest starts containers for services that the running service depends on. Use run to run tests or carry out an administrative task including doing away with or including data to a data extent field. The run command acts like docker run -ti in that it opens an interactive terminal to the container and returns an exit status matching the go out status of the method inside the container.

docker-compose-start command is beneficial handiest to restart containers that had been formerly created howeverwere stopped. It in no way creates new containers.

 

What is Docker Swarm?

Docker Swarm can be excellent understood because the native way of Clustering implementation for Docker itself. Docker Swarm turns a pool of Docker hosts right into a single and virtual Docker host. It serves the usual Docker API or any other tool that may already communicate with a Docker daemon can make use of Docker Swarm to scale in a obvious way to more than one hosts. Following are the listing of a number of the supported tools as a way to be useful in achieving what we have mentioned just now.

• Dokku

• Docker Compose

• Docker machine

• Jenkins

 

What is Dockerfile used for?

Docker file is nothing but a set of commands that need to be surpassed on to Docker itself, so that it can construct images automatically studying these commands from that particular Docker file. A Docker file is a textual content file that consists of all of the instructions a user ought to call at the command line to bring together an image. Using docker build users can create an automatic build that executes several command-line commands in succession.

 

How to create Docker container?

You could create a Docker container out of any particular Docker image of your desire and the identical may be finished the use of the command given below:

docker run -t -i command name

The command above will create the container and additionally begins it for you. so as to test whether the Docker container is created and whether or not it is running or not, you can employ the following command. This command will listing out all the Docker containers along with its statuses on the host that the Docker container runs.

docker ps -a

 

How to stop and restart the Docker container?

The following command can be used to stop a certain Docker container with the container id as

CONTAINER_ID:docker stop CONTAINER_ID

the subsequent command may be used to restart a certain Docker container with the container id as

CONTAINER_ID:docker restart CONTAINER_ID

 

Mention some usually used Docker Commands?

A few of the most normally used Docker commands are as follows:

 

Command   

Description

Dockerd   

Launch the Docker Daemon

Info   

Displays information System-Wide

Version   

Displays the Docker Version information

Build   

Builds images for Docker files

Inspect   

Returns low-level information on an image or container

History   

Shows Image History

Commit   

Creates new images from Container changes

Attach   

Attaches to a running container

Load   

Load an image from STDIN or tar archive

Create   

Create a new container

Diff   

Inspect changes on a container’s file system

Kill   

Kill a running container

 

 

 

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