├── .idea
├── .gitignore
├── docker-Interview-Questions-and-Answers.iml
├── misc.xml
├── modules.xml
└── vcs.xml
├── Makefile
├── README.md
├── docker-command.md
├── docker-compose.md
├── docker-container.md
├── docker-file.md
├── docker-image.md
├── docker-swarm.md
└── docker.png
/.idea/.gitignore:
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1 | # Default ignored files
2 | /shelf/
3 | /workspace.xml
4 | # Editor-based HTTP Client requests
5 | /httpRequests/
6 | # Datasource local storage ignored files
7 | /dataSources/
8 | /dataSources.local.xml
9 |
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/Makefile:
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1 | branch := $(shell git branch --show-current)
2 |
3 | .PHONY: cm
4 | cm: ## 🌱 git commit
5 | git add .
6 | git commit -m "$(branch)"
7 | git push origin $(branch)
8 |
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/README.md:
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1 | # docker Interview Questions and Answers
2 | Docker is a platform designed to help developers build, share, and run modern applications
3 | 
4 |
5 | * [docker command](docker-command.md)
6 | * [docker compose](docker-compose.md)
7 | * [docker container](docker-container.md)
8 | * [docker file](docker-file.md)
9 | * [docker images](docker-image.md)
10 | * [docker swarm](docker-swarm.md)
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/docker-command.md:
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1 | # Docker Commands Interview Questions and Answers
2 |
3 | ## What are some popular container orchestration systems?
4 | Some popular container orchestration systems are Kubernetes, Apache Mesos, and Docker Swarm.
5 |
6 | ## Which of the following commands creates a new container instance?
7 | docker run
8 |
9 | ## docker start
10 | The docker start command is used to start one or more stopped containers.
11 |
12 | ## docker stop
13 | The docker stop command is used to stop one or more running containers.
14 |
15 | ## docker build
16 | The docker build command is used to build an image from a Dockerfile.
17 |
18 | ## docker run
19 | The docker run command is used to run a container from an image.
20 |
21 | ## docker create
22 | The docker create command is used to create a new container from an image. This command will create a new container but will not start it. To start the container, you will need to use the docker start command.
23 |
24 | ## docker run
25 | The docker run command is used to launch a new container from a given image. This command takes in a number of different parameters and options that can be used to customize the container that is created. For example, you can use the docker run command to specify the name of the new container, the port mapping for the container, the environment variables for the container, and so on.
26 |
27 | ## docker instantiate
28 | The docker instantiate command creates a new container from a given image, but with a different set of environment variables than the original image. This can be useful for creating different versions of the same image with different settings.
29 |
30 | ## Which of the following commands would be most appropriate for creating a new container?
31 | The most appropriate command for creating a new container would be “docker run.” This command will create a new container with the specified image and run it.
32 |
33 | ## docker launch
34 | There are a few different ways to launch a Docker container. The most common way is to use the “docker run” command. This command will launch a new container with the specified image.
35 |
36 | ## docker ps
37 | The “docker ps” command will list all of the running containers on your system.
38 |
39 | ## docker stop
40 | The “docker stop” command will stop a running container.
41 |
42 | ## docker build
43 | The docker build command is used to create a new Docker image from a given Dockerfile. This command will take in the path to the Dockerfile as its first argument, and then an optional tag name for the new image as its second argument. If no tag name is specified, then the new image will be given the “latest” tag by default.
44 |
45 | ## docker run
46 | The docker run command is used to launch a new container from a given image. This command takes in a number of different parameters and options that can be used to customize the container that is created. For example, you can use the docker run command to specify the name of the new container, the port mapping for the container, the environment variables for the container, and so on.
47 |
48 | ## docker create
49 | The docker create command is used to create a new container from an image. This command will create a new container but will not start it. To start the container, you will need to use the docker start command.
50 |
51 | ## Which of the following commands can be used to remove all unused images on your machine?
52 | The docker system prune command can be used to remove all unused images on your machine.
53 |
54 | ## docker rmi -f $(docker images)
55 | This command will remove all of the images stored on your local machine.
56 |
57 | ## docker rm -f $(docker ps -a -q)
58 | Answer: This command will remove all of the containers stored on your local machine, regardless of whether or not they are running.
59 |
60 | ## docker rm -f $(docker images)
61 | This command will remove all of the images that are currently stored in your Docker instance. This can be useful if you want to start from scratch or if you want to clear up some disk space.
62 |
63 | ## docker system prune -a
64 | The docker system prune command will remove all unused data from your Docker system. This includes things like unused containers, images, volumes, and networks. The -a flag will also remove any data that is not associated with a running container, which can be useful for cleaning up after experiments or one-off tasks.
65 |
66 | ## docker cleanup -all
67 | The docker cleanup command is used to remove all unused containers, images, and volumes from your system. This can be helpful if you are running low on disk space, or if you want to clean up your system to prepare for a new Docker installation.
68 |
69 | ## Which of the following commands attaches your terminal session to a running container?
70 | docker attach
71 |
72 | ## docker attach [container-name]
73 | The docker attach command will allow you to attach to a running container. This is useful if you want to check on the status of a running container or if you need to troubleshoot an issue.
74 |
75 | ## docker build [path-to-Dockerfile]
76 | Answer: The docker build command is used to build a Docker image from a Dockerfile. This is the first step in creating a container.
77 |
78 | ## docker commit [container-name] [new-image-name]
79 | Answer: The docker commit command will create a new image from a container. This is useful if you have made changes to a container and want to save those changes as a new image.
80 |
81 | ## docker cp [container-name]:[path-to-file] [destination-path]
82 | Answer: The docker cp command will allow you to copy files from a container to your local machine. This is useful if you need to retrieve files from a container for troubleshooting or analysis.
83 |
84 | ## docker create [image-name]
85 | Answer: The docker create command will create a new container from an image. This is the first step in running a container.
86 |
87 | ## docker diff [container-name]
88 | Answer: The docker diff command will show you the differences between a container and its image. This is useful for troubleshooting or for understanding what changes have been made to a container.
89 |
90 | ## docker events
91 | Answer: The docker events command will show you a stream of events from the Docker daemon. This is useful for monitoring the status of your Docker environment.
92 |
93 | ## docker exec -it [container-name] [command]
94 | Answer: The docker exec command will allow you to run a command inside of a container. This is useful for troubleshooting or for running one-off commands inside of a container.
95 |
96 | ## docker export [container-name] > [filename.tar]
97 | Answer: The docker export command will export a container as a tar file. This is useful for creating backups of containers or for moving containers to another Docker environment.
98 |
99 | ## docker history [image-name]
100 | Answer: The docker history command will show you the history of an image. This is useful for understanding how an image was created or for troubleshooting issues with an image.
101 |
102 | ## docker images
103 | Answer: The docker images command will show you a list of all images on your system. This is useful for managing your images and for understanding what images are available.
104 |
105 | ## docker import [filename.tar] [new-image-name]
106 | Answer: The docker import command will import a tar file as a new image. This is useful for importing backups of containers or for moving containers to another Docker environment.
107 |
108 | docker kill
109 |
110 | ## docker connect [container-name]
111 | The docker connect command is used to connect a running container to a network. This is useful for when you want to connect a container to a specific network in order to access resources on that network.
112 |
113 | ## docker link [container-name]
114 | The docker link command is used to connect a running container to another running container. This is useful for linking together different applications or services that need to communicate with each other. For example, if you have a web server container and a database container, you can link them together so that the web server can access the database.
115 |
116 | ## docker join [container-name]
117 | The docker join command allows you to join an existing container to a new or existing network. This can be useful if you need to connect to a container that is running on a different host.
118 |
119 | ## Which of the following commands can be used to find out which network interfaces are being used by a container?
120 | The `docker network inspect` command can be used to find out which network interfaces are being used by a container.
121 |
122 | ## docker inspect –networks [container-name]
123 | This command will give you information about the network settings for a given container. This can be useful for troubleshooting networking issues, or for understanding how a container is configured.
124 |
125 | ## docker network create [network-name]
126 | Answer: This command will create a new network with the given name. This can be useful for creating isolated networks for testing or development purposes.
127 |
128 | ## docker network rm [network-name]
129 | Answer: This command will remove the given network. This can be useful for cleanup purposes, or for removing unused networks.
130 |
131 | ## docker inspect –network [container-name]
132 | The docker inspect command is a powerful tool that can be used to retrieve detailed information on one or more containers. The –network option can be used to specifically retrieve information on the network settings for a given container. This can be useful for troubleshooting networking issues, or for simply understanding how a container is configured.
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/docker-compose.md:
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1 | # Docker Compose Interview Questions and Answers
2 |
3 | ## Can you explain what Docker Compose is?
4 | Docker Compose is a tool that helps you manage multi-container Docker applications. With Compose, you can define a single application that consists of multiple services, and then run that application in a single process. This makes it easy to coordinate your application’s services and ensures that they are all running in the correct order.
5 |
6 | ## What are the main benefits of using Docker Compose for docker containers?
7 | Docker Compose is a great tool for managing docker containers because it allows you to define all of your containers and their configurations in a single yaml file. This makes it easy to spin up and down entire applications made up of multiple containers with a single command. Additionally, Docker Compose can be used to define environment variables, link containers together, and specify which ports should be exposed.
8 |
9 | ## What are some important features of Docker Compose?
10 | Docker Compose is a tool for defining and running multi-container Docker applications. With Compose, you use a YAML file to configure your application’s services. Then, with a single command, you create and start all the services from your configuration.
11 |
12 | ## How can you install Docker Compose on a Linux box?
13 | You can install Docker Compose on a Linux box by running the following command:
14 |
15 | ```
16 | sudo curl -L “https://github.com/docker/compose/releases/download/1.25.4/docker-compose-$(uname -s)-$(uname -m)” -o /usr/local/bin/docker-compose
17 |
18 | sudo chmod +x /usr/local/bin/docker-compose
19 | ```
20 |
21 |
22 | ## Can you give me an example of how to use Docker Compose with MySQL and PHPMyAdmin?
23 | Here’s an example of how you could use Docker Compose with MySQL and PHPMyAdmin.
24 |
25 | In your docker-compose.yml file, you would first need to specify the versions of each component that you’re using:
26 |
27 | ```yaml
28 | version: ‘3’
29 | services:
30 | db:
31 | image: mysql:5.7
32 | volumes:
33 | – db_data:/var/lib/mysql
34 | restart: always
35 | environment:
36 | MYSQL_ROOT_PASSWORD: somewordpress
37 | MYSQL_DATABASE: wordpress
38 | MYSQL_USER: wordpress
39 | MYSQL_PASSWORD: wordpress
40 |
41 | wordpress:
42 | depends_on:
43 | – db
44 | image: wordpress:latest
45 | ports:
46 | – “8000:80”
47 | restart: always
48 | environment:
49 | WORDPRESS_DB_HOST: db:3306
50 | WORDPRESS_DB_USER: wordpress
51 | WORDPRESS_DB_PASSWORD: wordpress
52 | WORDPRESS_DB_NAME: wordpress
53 | ```
54 | This will start up a MySQL database and a WordPress instance that is connected to it. You can then access PHPMyAdmin by going to http://localhost:8000/phpmyadmin in your browser.
55 |
56 | ## What is the purpose of the docker-compose command in Docker?
57 | The docker-compose command is used to define and run multi-container Docker applications. With Compose, you use a YAML file to configure your application’s services. Then, with a single command, you create and start all the services from your configuration.
58 |
59 | ## What’s the difference between up, start and run in Docker Compose?
60 | The main difference between up, start and run is that up also builds the images for you, whereas start and run assume that the images already exist. Start and run are essentially the same, except that run will also execute a command in the container once it starts up.
61 |
62 | ## Is it possible to specify multiple compose files when running a container from Docker Compose? If yes, then how?
63 | Yes, it is possible to specify multiple compose files when running a container from Docker Compose. You can do this by using the -f flag followed by the path to the desired compose file. For example, if you wanted to use two compose files named file1.yml and file2.yml, you would use the following command: docker-compose -f file1.yml -f file2.yml up
64 |
65 | ## What do you understand about services and networks as used by Docker Compose?
66 | Services are defined in a docker-compose.yml file and are essentially a collection of containers that are deployed together. A network is a virtual network that allows containers to communicate with each other.
67 |
68 | ## What are some common operations that can be performed using Docker Compose CLI commands?
69 | Some common operations that can be performed using Docker Compose CLI commands include creating and starting containers, stopping and removing containers, and viewing logs.
70 |
71 | ## Can you explain what environment variables are and what role they play in Docker Compose?
72 | Environment variables are variables that are set outside of the Docker Compose file and are used to configure the containers that are created when you run “docker-compose up”. These variables can be used to set things like the hostname or IP address of a container, the username and password for a database, or any other number of things.
73 |
74 | ## What happens if certain configuration values are not specified in a Docker Compose file?
75 | If certain configuration values are not specified in a Docker Compose file, then the default values for those settings will be used. For example, if you do not specify a particular network mode, then the default network mode will be used.
76 |
77 | ## Is there any way to override default settings like port numbers when using Docker Compose? If yes, then how?
78 | Yes, it is possible to override the default settings in a docker-compose.yml file. You can do this by specifying the desired setting in the file, and then using the override command when starting up your containers.
79 |
80 | ## What is your opinion on using .yml vs .yaml extension for Docker Compose files?
81 | I don’t really have a strong opinion on the matter. I think that either extension would be fine to use.
82 |
83 | ## What are build instructions and why are they useful while working with Docker Compose?
84 | Build instructions are a set of commands that are used to build an image from a Dockerfile. These instructions are generally used when you are working with a team of developers and need to ensure that everyone is using the same image. By specifying the build instructions in the docker-compose.yml file, you can ensure that everyone on your team is using the same image when they build their containers.
85 |
86 | ## What is the significance of the restart directive in Docker Compose?
87 | The restart directive is used to specify whether or not a container should be restarted if it is stopped for any reason. By default, containers are not restarted if they are stopped. However, you can use the restart directive to tell Docker Compose to always restart a particular container if it is stopped. This can be useful if you have a container that is critical to your application and you want to make sure that it is always running.
88 |
89 | ## What is the order of execution of directives specified in a Docker Compose file?
90 | The order of execution of directives in a Docker Compose file is as follows:
91 | 1. build
92 | 2. image
93 | 3. command
94 | 4. depends_on
95 | 5. links
96 | 6. ports
97 | 7. volumes
98 | 8. environment
99 | 9. net
100 | 10. dns
101 | 11. dns_search
102 | 12. extra_hosts
103 | 13. depends_on
104 | 14. extends
105 | 15. external_links
106 | 16. log_driver
107 | 17. log_opt
108 | 18. pid
109 | 19. restart
110 | 20. security_opt
111 | 21. shm_size
112 | 22. ulimits
113 | 23. user
114 | 24. working_dir
115 |
116 | ## What is the best approach to follow while writing Docker Compose files?
117 | There is no one-size-fits-all answer to this question, as the best approach to writing Docker Compose files will vary depending on your specific needs and preferences. However, some tips that may be helpful include keeping your files as concise and readable as possible, using comments to explain your choices, and using named volumes rather than anonymous volumes wherever possible.
118 |
119 | ## What do you think is the best way to manage configs across environments when using Docker Compose?
120 | There are a few different ways to manage configs across environments when using Docker Compose. One option is to use environment variables, which can be easily set and updated as needed. Another option is to use a separate config file for each environment, which can be loaded into Docker Compose as needed. Finally, you could also use a tool like Consul to manage your configs, which would provide a central location for all of your configs and make it easy to update them as needed.
121 |
122 | ## What are some security concerns related to Docker Compose?
123 | One of the main security concerns related to Docker Compose is that it can be used to create what are known as “container sprawl” issues. This happens when too many containers are created and not all of them are properly managed, leading to a situation where it becomes difficult to keep track of all of them and ensure that they are all secure. Another concern is that Docker Compose can be used to create “fat containers” which are containers that have a lot of unnecessary data and files in them, which can lead to security issues if those files are not properly secured.
124 |
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/docker-container.md:
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1 | # Docker Containers Interview Questions and Answers
2 |
3 | ## What is Docker?
4 | * Docker is a tool that enables you to create, deploy, and run applications inside of self-contained “containers.” This allows for much greater portability and flexibility when it comes to developing and deploying applications.
5 |
6 |
7 | * Docker is a tool that helps you create, deploy, and run applications by using containers. Containers allow you to package up an application with all of the parts it needs, such as libraries and other dependencies, and ship it all out as one package. This means that your application will always run the same, regardless of the environment it is running in.
8 |
9 |
10 | ## Can you explain some of the main components and concepts associated with Docker?
11 | Some of the main components and concepts associated with Docker include images, containers, layers, and registries. Images are used to create containers, which are self-contained environments that can be run on any compatible host. Layers are used to create images, and registries are used to store and distribute images.
12 |
13 | ## How are containers different from virtual machines?
14 | Containers are different from virtual machines in a few key ways. First, containers don’t require their own dedicated operating system – they can share the host operating system with other containers. This makes them much more lightweight and efficient than virtual machines. Second, containers are designed to be immutable – once you create and deploy a container, you shouldn’t need to make any changes to it. This makes them much easier to manage and keep track of than virtual machines, which can often become “snowflakes” over time as they are updated and changed.
15 |
16 | ## What are some key features of a container?
17 | Containers are isolated from each other and the underlying host operating system. This allows for consistent runtime environments and makes it easy to package and deploy applications. Containers are also lightweight and fast, making them ideal for microservices and other distributed applications.
18 |
19 | ## Why do we need to use containers in development environments?
20 | Containers provide a consistent development environment that can be used on any machine, regardless of operating system. This makes it easy to develop and test applications on different machines without having to worry about inconsistencies between environments.
21 |
22 | ## How can you achieve scalability when using containers?
23 | One way to achieve scalability when using containers is to use a container orchestration tool like Kubernetes. This tool can help you manage a large number of containers and ensure that they are all running smoothly. Another way to achieve scalability is to use a container management platform like Docker Swarm. This platform can help you to deploy and manage a large number of containers across multiple servers.
24 |
25 | ## What is the basic command used for creating an image in Docker?
26 | The basic command for creating an image in Docker is “docker build.” This command will take the necessary files and create an image that can be used to create a container.
27 |
28 | ## Is it possible to run multiple commands at once in Docker? If yes, then how?
29 | Yes, it is possible to run multiple commands at once in Docker. This can be accomplished by using the “&&” operator to chain the commands together. For example, if you wanted to run the commands “ls” and “pwd” at the same time, you would use the following command:
30 |
31 | ```docker run -it –rm myimage sh -c “ls && pwd”```
32 |
33 | ## What’s the difference between a Docker image and a Docker container?
34 | A Docker image is a read-only template that contains a set of instructions for creating a Docker container. Images are used to create containers. A Docker container is a runnable instance of an image—it is the combination of an image and the command that was used to create it.
35 |
36 | ## What is the basic command that should be used to stop a running container?
37 | The basic command to stop a running container is “docker stop.” This command will send a SIGTERM signal to the container, which will cause it to shut down gracefully.
38 |
39 | ## What are some of the most commonly used Docker commands?
40 | The most commonly used Docker commands are:
41 |
42 | * docker build: Used to build a new Docker image from a Dockerfile
43 | * docker run: Used to launch a new Docker container from an existing image
44 | * docker pull: Used to pull a Docker image from a registry
45 | * docker push: Used to push a Docker image to a registry
46 |
47 | ## What is a bridge in Docker?
48 | A bridge is a virtual network device that connects Docker containers to each other and to the outside world. By default, every container is attached to a bridge called “docker0”.
49 |
50 | ## What happens when you run a dockerized application on a server?
51 | When you run a dockerized application on a server, the application is packaged into a container along with all of its dependencies. The container is then run on the server, allowing the application to be isolated from the rest of the system. This makes it easy to deploy and run applications on servers, as they can be run in any environment that supports Docker.
52 |
53 | ## What does the “docker ps” command do?
54 | The “docker ps” command lists all of the running Docker containers on a system.
55 |
56 | ## What’s the best way to handle two containers that require a shared volume?
57 | There are a few different ways to handle two containers that require a shared volume, but the best way may depend on your specific use case. One option is to use a named volume, which can be created using the docker volume create command. This will allow both containers to access the volume by name. Another option is to use a host volume, which can be created by mounting a host directory into the container. This can be done using the -v flag when starting the container.
58 |
59 | ## What is a Docker daemon?
60 | A Docker daemon is a process that runs on a host machine and is responsible for building and running Docker containers. The daemon listens for API requests from Docker clients and handles the heavy lifting of building and running containers.
61 |
62 | ## Can you explain what namespaces are in context with Docker?
63 | Namespaces are a Linux kernel feature that allows for complete isolation between different processes running on a single system. This is accomplished by giving each process its own virtual view of the system, which means that they are unable to see or interact with any other processes outside of their namespace. Docker containers make use of this feature to provide complete isolation between the different containers running on a single host.
64 |
65 | ## What are control groups and how do they work?
66 | Control groups are a Linux kernel feature that allows system administrators to group processes together and manage them as a unit. This can be useful for a number of reasons, such as limiting the amount of resources that a particular group of processes can use, or isolating a group of processes from each other. Control groups are implemented in the Linux kernel and are used by a number of containerization technologies, including Docker.
67 |
68 | ## What is Docker Hub?
69 | Docker Hub is a cloud-based registry service for storing and sharing Docker images. With Docker Hub, you can create and manage your own repositories, either public or private, and share images with other Docker users.
70 |
71 | ## What are the main benefits of using Docker containers?
72 | The main benefits of using Docker containers are that they are portable, lightweight, and easy to use. Docker containers can be used to package and ship applications quickly and easily, and they can be run on any platform that supports Docker. Containers are also much lighter weight than virtual machines, so they can be deployed and run more quickly.
73 |
74 | ## Can you explain what a container is in the context of Docker?
75 | A container is a self-contained unit of software that includes everything needed to run an application: code, runtime, system tools, system libraries, etc. Containers are isolated from each other and can communicate with each other through well-defined channels. All containers are run by a single operating system kernel and share that kernel with other containers. This makes them much more efficient than virtual machines, which typically run on top of a hypervisor and have their own kernel.
76 |
77 | ## How do you go about creating and running a new container with Docker?
78 | The first step is to create a new Dockerfile. This file will contain all of the instructions necessary to build your container. Once your Dockerfile is ready, you can then use the ‘docker build’ command to create your container. Finally, once your container is built, you can use the ‘docker run’ command to launch it.
79 |
80 | ## What’s the difference between a Docker image and a container?
81 | A Docker image is a read-only template that contains a set of instructions for creating a Docker container. Images are used to create containers. A container is a runnable instance of an image—what the image becomes in memory when actually executed. It runs completely isolated from the host environment by default, only accessing host files and ports if configured to do so.
82 |
83 | ## How can you ensure that your container only runs one process at a time?
84 | By default, Docker containers will run multiple processes at the same time. However, you can use a tool like Supervisor to help manage and monitor processes inside of a container so that only one process is running at a time.
85 |
86 | ## Why should I use port-mapping instead of directly exposing ports on a container? What are the advantages?
87 | By port-mapping, you can control which host ports are mapped to which container ports. This gives you more flexibility and security, as you can change the host port mapping at any time without having to change the container configuration. Additionally, it is generally considered more secure to not expose container ports directly to the host, as this can open up the host to potential attacks.
88 |
89 | ## How can you build an image from a Dockerfile?
90 | You can build an image from a Dockerfile using the docker build command. This command will take a Dockerfile as input and produce a new image as output.
91 |
92 | ## What is the purpose of a Docker volume? When would you use it?
93 | A Docker volume is a directory that is used to store data for a Docker container. This data is stored outside of the container itself, which means that it is not deleted when the container is deleted. This can be useful for storing data that needs to be persistent, such as a database.
94 |
95 | ## What’s the best way to copy files into a container? Is there any disadvantage of doing so?
96 | The best way to copy files into a container is to use the docker cp command. This command will allow you to copy files from your host machine into a running container. The disadvantage of using this method is that it can be slow, and if you are copying a large number of files, it can take up a lot of disk space.
97 |
98 | ## How does Linux Containers compare to Docker containers?
99 | Docker containers are a type of Linux container. Linux containers are a way to isolate processes from each other on a single host, allowing multiple processes to run on a single host without them interfering with each other. Docker containers add an additional layer of abstraction on top of Linux containers, making it easier to package and deploy applications.
100 |
101 | ## Can you explain what container orchestration is and why it’s important?
102 | Container orchestration is the process of managing and coordinating multiple containers so that they can work together to achieve a common goal. This is important because it allows for the efficient use of resources and ensures that all containers are able to communicate with each other and work together as intended.
103 |
104 |
105 | ## What does the -v flag mean when starting a new container? Give me some examples.
106 | The -v flag stands for volume, and it is used to mount a volume from the host machine into the container. This is useful for data that needs to be persisted outside of the container, such as logs or application data. For example, if you have a web application that is running in a container, you might use the -v flag to mount the application’s data directory into the container so that the data is not lost if the container is stopped or deleted.
107 |
108 | ## Is it possible to run multiple processes inside a single container? If yes, then how?
109 | Yes, it is possible to run multiple processes inside a single container. This can be accomplished by using a process manager, such as Supervisord. Supervisord can be used to start, stop, and monitor multiple processes inside a single container.
110 |
111 | ## Can you list out all the parameters available for configuring a Docker container?
112 | There are a number of parameters that can be configured when setting up a Docker container, including:
113 |
114 | * CPU shares: This parameter sets the relative amount of CPU time that a container can use.
115 | * Memory: This parameter sets the amount of memory that a container can use.
116 | * Network mode: This parameter sets the networking mode for a container, which can be either “bridge” (the default), “host”, or “none”.
117 | * Restart policy: This parameter sets the policy for automatically restarting a container.
118 | * Volumes: This parameter sets the volumes that should be mounted inside a container.
119 |
120 | ## What is the syntax for accessing environment variables defined in the host machine from within a docker container?
121 | The syntax for accessing environment variables defined in the host machine from within a docker container is:
122 |
123 | ```${HOST_ENV_VAR}```
124 |
125 | ## Why would you want to create aliases for commonly used commands in Docker?
126 | By creating aliases for commonly used commands in Docker, you can save time and typing by having the commands automatically expanded to their full form. This can be particularly useful if you are working with long or complex commands that you don’t want to have to remember or type out in full every time.
127 |
128 | ## How can you cleanly shut down a container without losing data?
129 | The best way to cleanly shut down a container without losing data is to use the commit command. This command will take a snapshot of the container’s current state and save it as a new image. Once you have done this, you can then use the stop command to gracefully shut down the container.
130 |
131 | ## What do you understand by “daemonized Docker containers”? What do they have to do with sidecar patterns?
132 | Daemonized Docker containers are those that have been configured to run in the background as a daemon process. This is often done in order to keep the container running even if the user logs out of the host machine. Sidecar patterns are a way of structuring daemonized Docker containers so that they can work together to provide a complete service. This often involves one container running the actual service and another container running a process to monitor and manage the service.
133 |
134 | ## How do you manage access control to a Docker daemon socket?
135 | By default, the Docker daemon socket is only accessible to the root user. This means that any user who wants to access the Docker daemon must have root privileges. However, it is possible to change this so that the Docker daemon is accessible to non-root users. To do this, you can create a Unix group called docker and add any users who should have access to the Docker daemon to that group.
136 |
137 | ## What is the best way to make sure that my container doesn’t consume too much memory?
138 | One way to make sure that your container doesn’t consume too much memory is to use a tool like cgroups-limit to set a maximum limit on the amount of memory that the container can use. You can also use a tool like Docker Compose to specify memory limits for your containers.
139 |
140 | ## What are the various ways to configure a Docker network?
141 | There are three ways to configure a Docker network:
142 |
143 | * By using the –net option when starting a container
144 | * By using the –link option when starting a container
145 | * By using the docker network command
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/docker-file.md:
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1 | # Dockerfile Interview Questions and Answers
2 |
3 | ## What is a Dockerfile?
4 | A Dockerfile is a text file that contains all the commands a user could call on the command line to assemble an image. Using a Dockerfile removes the need to manually create a Docker image.
5 |
6 | ## Can you explain the components of a Dockerfile?
7 | A Dockerfile is a text file that contains all the commands a user could call on the command line to assemble an image. Using a Dockerfile removes the need to manually create a Docker image, and instead allows the user to create one automatically. A Dockerfile consists of six components: the FROM instruction, the MAINTAINER instruction, the RUN instruction, the CMD instruction, the ENTRYPOINT instruction, and the VOLUME instruction.
8 |
9 | ## How do you run a Docker container in foreground mode and detached mode?
10 | To run a Docker container in foreground mode, you would use the command “docker run -it “. To run a Docker container in detached mode, you would use the command “docker run -d “.
11 |
12 | ## Is it possible to configure memory limits for containers? If yes, then how?
13 | Yes, it is possible to configure memory limits for containers. You can do this by using the “memory” flag when starting up the container. For example, if you wanted to limit a container to 512 MB of memory, you would use the following command:
14 | ```docker run -it –memory 512m my_container```
15 |
16 | ## What’s the difference between docker pull and docker build?
17 | Docker pull is used to download a Docker image from a registry. Docker build is used to create a Docker image from a Dockerfile.
18 |
19 | ## What are the different types of networking configurations available with Docker?
20 | There are three types of networking configurations available with Docker: bridge, host, and none. Bridge networking is the most common and creates a private network between the host and containers. Host networking uses the host machine’s network directly, and none networking disables all networking.
21 |
22 | ## Can you give me an example of the syntax used to create a new image using the docker commit command?
23 | The docker commit command is used to create a new image from a container. The syntax for this command is:
24 |
25 | ```docker commit [container-id] [new-image-name]```
26 |
27 | ## How can I get a list of all images present on my system?
28 | You can use the “docker images” command to get a list of all images present on your system.
29 |
30 | ## Why do we need Dockerfiles?
31 | Dockerfiles are important because they allow us to create reproducible images for our Docker containers. By creating a Dockerfile, we can specify all of the dependencies and configurations that our container will need in order to run, which makes it much easier to deploy our applications.
32 |
33 |
34 | ## What does the -it flag mean when using docker run?
35 | The -it flag stands for “interactive” and “tty”. This means that when you use this flag, you are telling Docker to allocate a pseudo-TTY connected to the container’s stdin. This allows you to interact with the container as if it were a running process on your host.
36 |
37 | ## Can you tell me some examples of official repositories that come as part of the default library set up with Docker?
38 | Some examples of official repositories that come as part of the default library set up with Docker are Ubuntu, CentOS, and Debian.
39 |
40 | ## In what context would you use a Dockerfile to define a container?
41 | A Dockerfile is a text file that contains all the commands a user could call on the command line to assemble an image. Using a Dockerfile is an alternative to using the command line to create a new container.
42 |
43 | ## What are some advantages of using Docker over other configuration management tools like Puppet or Chef?
44 | One advantage of using Docker is that it can be used to create light-weight, portable, self-contained images of an application and its dependencies. This makes it easy to deploy and run applications in different environments. Additionally, Docker can be used to create isolated development environments, which can be helpful when working on projects with multiple dependencies.
45 |
46 | ## What do you understand by layered architecture of Docker images?
47 | The layered architecture of Docker images is a key part of what makes them so efficient. Each layer in a Docker image is built on top of the previous layer, with the base layer being the only one that is not dependent on any other layer. This allows for each layer to be much smaller in size, as it only needs to contain the changes from the previous layer. This also makes it much easier to share Docker images, as each layer can be reused by multiple images.
48 |
49 | ## Why do developers prefer to use Docker?
50 | Developers prefer to use Docker because it makes it easy to package and ship applications. Docker containers are lightweight and can be run on any platform that supports Docker. This makes it easy to deploy applications on any server or cloud platform.
51 |
52 | ## What is your understanding of multi-stage builds in Docker? How can they be achieved?
53 | Multi-stage builds are a way of optimizing Dockerfiles to create smaller, more efficient images. They work by allowing you to specify multiple FROM statements in a single Dockerfile, each of which can use a different base image. This way, you can avoid having to duplicate code or files between different stages of the build process. To achieve a multi-stage build, simply specify multiple FROM statements in your Dockerfile, each with a different base image.
54 |
55 | ## What are some examples of services provided by Docker Hub?
56 | Docker Hub is a cloud-based registry service that allows you to link to code repositories, test and deploy images, and manage webhooks.
57 |
58 | ## What is the best way to link volumes from a host to a container in Docker?
59 | The best way to link volumes from a host to a container in Docker is to use the -v flag when starting the container. This will allow you to specify the host directory that you want to mount as a volume inside the container.
60 |
61 | ## What do you understand about the concept of linking in Docker?
62 | Linking is a way for one container to access the files or services of another container. This is useful if you have multiple containers that need to share data or if you want to connect to a database container from your application container. To link containers, you use the –link flag when you create a new container.
63 |
64 | ## What is the purpose of the EXPOSE keyword in Dockerfiles?
65 | The EXPOSE keyword is used to indicate which ports the container will be listening on at runtime. This is useful for linking containers together, as well as for allowing outside access to the container.
66 |
67 | ## What are some reasons why one should avoid running privileged containers?
68 | Running a privileged container gives the container full access to the host machine, which can be a security risk. If the container is compromised, the attacker could gain full control of the host. Additionally, privileged containers can be a risk to the stability of the host machine, as they can potentially interfere with other containers or the host itself.
69 |
70 |
71 |
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/docker-image.md:
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1 | # Docker Image Interview Questions and Answers
2 |
3 | ## What is a Docker image?
4 | A Docker image is a read-only template that contains a set of instructions for creating a Docker container. It includes everything that the container needs to run, including the operating system, application code, runtime dependencies, and any other files needed for the application to run.
5 |
6 | ## What’s the difference between an image and a container?
7 | An image is a read-only template with instructions for creating a Docker container. A container is a runnable instance of an image—what the image becomes in memory when actually executed. It runs completely isolated from the host environment by default, only accessing host files and ports if configured to do so.
8 |
9 | ## How are images created in Docker?
10 | Images are created in Docker through a process called “docker build.” This process takes a “Dockerfile” – a file that contains all of the instructions for building the image – and uses that to create an image.
11 |
12 | ## Can you explain what layers are in context with Docker images?
13 | Layers are basically the differences between two versions of a Docker image. Every time a change is made to a Docker image, a new layer is created. Layers are then used to create new versions of the image, with each new version having all of the changes from the previous layers.
14 |
15 | ## What do you understand about base images?
16 | Base images are the foundation of a Docker image. They are typically created by a team of developers and include the operating system, as well as any necessary dependencies and tools. Once a base image has been created, it can be used as the starting point for creating new images.
17 |
18 | ## What is the best way to build a multi-stage docker file?
19 | There is no one-size-fits-all answer to this question, as the best way to build a multi-stage docker file will vary depending on the specific needs of your project. However, some tips on how to build a multi-stage docker file include using a separate stage for each major component of your application, using a base image that is compatible with the rest of your application, and using caching to improve build times.
20 |
21 | ## What is scratch in Docker images?
22 | Scratch is a special type of Docker image that contains no files or directories. It is essentially an empty image that can be used as a starting point for building other images. You can add files and directories to a scratch image using the ADD or COPY commands in a Dockerfile.
23 |
24 | ## What is the format of a Docker image?
25 | The format of a Docker image is a tar archive, compressed using gzip.
26 |
27 | ## Is it possible to run multiple containers from a single image? If yes, then how?
28 | Yes, it is possible to run multiple containers from a single image. This can be done by using the docker run command with the -d option, which will start the container in detached mode.
29 |
30 | ## Does a Docker image have its own filesystem separate from the host machine?
31 | Yes, a Docker image has its own filesystem that is separate from the host machine. This is one of the benefits of using Docker images, as it allows for a more consistent and isolated development environment.
32 |
33 | ## What happens if two images share the same parent layer?
34 | If two images share the same parent layer, then any changes made to that parent layer will be reflected in both images. This can be useful if you want to make sure that two images are always in sync, but it can also lead to problems if you’re not careful. Make sure that you know what you’re doing before you start sharing layers between images!
35 |
36 | ## What does the push command do in Docker?
37 | The push command is used to push a Docker image to a registry. This is useful for sharing images with others or for keeping a backup of an image.
38 |
39 | ## What does the pull command do in Docker?
40 | The pull command is used to download a Docker image from a registry. A registry is a collection of images, and the Docker Hub is a popular registry that contains images for many common applications. To pull an image from the Docker Hub, you would use a command like “docker pull ubuntu” to pull the Ubuntu image.
41 |
42 | ## Are there any limitations on the size of Docker images?
43 | Yes, there are size limitations on Docker images. Images can’t be larger than 10 GB.
44 |
45 | ## What is the significance of tagging a Docker Image?
46 | Tagging a Docker Image allows you to give it a specific name and version. This is important because it allows you to track changes to the image over time, and also makes it easier to deploy specific versions of an image.
47 |
48 | ## What is the purpose of using volume mounts in Docker?
49 | Volume mounts are used to persist data generated by and used by Docker containers. By using volume mounts, you can ensure that data is not lost when a container is stopped or deleted. Additionally, volume mounts can be used to share data between containers.
50 |
51 | ## Is it possible to use Docker without a registry? Why or why not?
52 | Yes, it is possible to use Docker without a registry. However, without a registry, you will not be able to share your images with others. A registry is necessary in order to push and pull images.
53 |
54 | ## Can you give me some examples of popular public registries?
55 | Some popular public registries include Docker Hub, Quay.io, and Artifactory.
56 |
57 | ## What is the difference between Kubernetes and Docker Swarm?
58 | Kubernetes is a container orchestration tool that is used to manage a large number of containers. It is designed to automate the deployment, scaling, and management of containerized applications. Docker Swarm is a container orchestration tool that is used to manage a cluster of Docker hosts. It is designed to provide a simple and easy way to manage a group of Docker containers.
59 |
60 | ## What is the purpose of a manifest file in Docker Images?
61 | A manifest file is used to specify the configuration of a Docker image. This file contains information such as the image name, the version of the image, the list of dependencies, and more. The manifest file is used by Docker to build the image and make sure that all of the dependencies are met.
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/docker-swarm.md:
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1 | # Docker Swarm Interview Questions and Answers
2 |
3 | ## What is Docker Swarm?
4 | Docker Swarm is a tool that allows you to create and manage a cluster of Docker hosts. With Swarm, you can easily create a scalable and highly available application by using a simple set of commands.
5 |
6 | ## What are the main components of Docker Swarm?
7 | The main components of Docker Swarm are the manager and the workers. The manager is responsible for maintaining the cluster and ensuring that all of the workers are functioning properly. The workers are responsible for actually running the containers.
8 |
9 | ## Can you explain how a swarm is created in Docker?
10 | A swarm is created in Docker by using the “docker swarm init” command. This command will initialize the swarm and make it available for use.
11 |
12 | ## How do you join existing nodes and add new nodes to an existing Docker Swarm?
13 | In order to join an existing Docker Swarm, you will need to use the “docker swarm join” command. This command will allow you to join an existing Swarm as either a manager or a worker. You can also use this command to add new nodes to an existing Swarm.
14 |
15 | ## What types of resources can be used as secrets in Docker Swarm?
16 | Secrets in Docker Swarm can be used to store sensitive data such as passwords, API keys, and certificates. Secrets are encrypted and can only be accessed by services that have been granted explicit permission to do so.
17 |
18 | ## What’s the difference between secrets and configs, two newly introduced features of Docker 1.13?
19 | Secrets are encrypted and can be used to store sensitive data, such as passwords and API keys. Configs are not encrypted but can be used to store configuration information, such as database connection strings.
20 |
21 | ## Why is it recommended to use secrets instead of environment variables or other forms of configuration data with services running on Docker Swarm?
22 | Secrets are recommended for use with services running on Docker Swarm because they are encrypted and thus more secure. Environment variables and other forms of configuration data are not encrypted and thus are less secure.
23 |
24 | ## What is the best way to manage secrets for a service that needs access to multiple secrets?
25 | The best way to manage secrets for a service that needs access to multiple secrets is to use a secret management tool like Hashicorp Vault. This will allow you to securely store and manage your secrets, and will give you the ability to rotate them on a regular basis.
26 |
27 | ## What is the purpose of using stacks with Docker Swarm?
28 | The main purpose of using stacks is to provide a way to deploy and manage multiple services within a single application. This is especially useful when those services need to be deployed across multiple servers or when they need to be updated frequently. Using stacks allows you to define all of the services that make up your application in a single file, and then deploy and update them all at once.
29 |
30 | ## What are some common scenarios where Docker Swarm would be useful?
31 | Docker Swarm is a great tool for managing a cluster of Docker containers. It can be used to schedule and deploy containers across a cluster of servers, and also provides features for load balancing and failover. This makes it ideal for use in distributed applications or microservices.
32 |
33 | ## What are some drawbacks of using Docker Swarm?
34 | Some potential drawbacks of using Docker Swarm include:
35 |
36 | * The need for a separate orchestrator, which can add complexity
37 | * The potential for reduced performance due to container-level isolation
38 | * The lack of certain features compared to other container orchestration solutions, such as automatic rollbacks or health checks
39 |
40 | ## How does Docker Swarm handle failover when a node goes down?
41 | When a node goes down in a Docker Swarm, the other nodes in the cluster will take over its tasks. This ensures that there is no interruption in service and that the cluster as a whole remains operational.
42 |
43 | ## What happens if I have 5 tasks running on a five-node cluster and one of the nodes dies? Will the task re-schedule itself on another node?
44 | If one of the nodes in a Docker Swarm cluster dies, the tasks running on that node will be automatically rescheduled on another node in the cluster. This ensures that the tasks continue to run and that the cluster remains operational.
45 |
46 | ## How do you make sure your application scales efficiently across multiple nodes in Docker Swarm?
47 | There are a few things you can do to make sure your application scales efficiently in Docker Swarm. First, you need to make sure that your application is designed in a way that is scalable. This means that it can be easily divided into smaller pieces that can run independently. Second, you need to make sure that you are using the right type of container for your application. For example, if you are using a stateless application, then you can use a replicated container. This will allow you to run multiple copies of your application on different nodes. Finally, you need to make sure that you are monitoring your application so that you can identify any bottlenecks or issues that might arise.
48 |
49 | ## Is there a limit to the number of services that can be deployed to a single Docker Swarm Cluster?
50 | There is no limit to the number of services that can be deployed to a single Docker Swarm Cluster.
51 |
52 | ## What are the security implications of deploying a multi-service app to Docker Swarm?
53 | There are a few security implications to consider when deploying a multi-service app to Docker Swarm. First, you need to make sure that your services are properly isolated from each other. This can be done by using different containers for each service, or by using different networks. Second, you need to be aware of the potential for privilege escalation. If one service is compromised, an attacker could gain access to other services on the same host. Finally, you need to make sure that your secrets are properly managed. Secrets should not be stored in the same place as your code or your configuration.
54 |
55 | ## How do you make sure your containerized applications remain secure when they’re deployed to production?
56 | There are a few key things you can do to make sure your containerized applications remain secure when deployed to production. First, you should make sure you are using the latest versions of all your software components, including the operating system, application code, and any third-party libraries. Second, you should run your containers in a minimalistic fashion, only including the components and libraries that are absolutely necessary for the application to run. Finally, you should consider using a tool like Docker Bench for Security to scan your containers for common security issues.
57 |
58 | ## What are some ways to improve performance when scaling out containers in Docker Swarm?
59 | There are a few ways to improve performance when scaling out containers in Docker Swarm:
60 |
61 | * Use a load balancer to distribute traffic evenly across all containers
62 | * Use a caching layer to improve response times
63 | * Use a content delivery network (CDN) to improve performance for static content
64 |
65 | ## What is the difference between stateless and stateful services in Docker Swarm?
66 | Stateless services are those which do not maintain any data or state information. They can be scaled up or down without any data loss. Stateful services, on the other hand, do maintain data and state information. This means that if they are scaled down, data may be lost.
67 |
68 | ## If a Docker stack has more than one service, how do you scale them up at once?
69 | You can use the docker-compose scale command to scale up all services in a stack at once.
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