General

Question 1

What is Docker?

Answer 1

Docker is an open platform for developing, shipping, and running applications in containers.

Question 2

What are Docker containers?

Answer 2

Docker containers are lightweight, standalone, executable packages that include everything needed to run a piece of software, including the code, runtime, libraries, and settings.

Question 3

How does Docker differ from virtual machines?

Answer 3

Docker containers share the host system’s kernel and resources, making them more lightweight and efficient compared to virtual machines, which require a full OS instance for each VM.

Question 4

What command is used to list all Docker containers?

Answer 4

The command is ‘docker ps’ for running containers and ‘docker ps -a’ for all containers. PS stands for “Process Status”

Question 5

What file is used to define a multi-container Docker application?

Answer 5

A Docker Compose file, usually named ‘docker-compose.yml’, is used to define multi-container Docker applications.

Question 6

How do you build a Docker image from a Dockerfile?

Answer 6

Use the command ‘docker build -t image_name .’, where ‘image_name’ is your desired image name and ‘.’ specifies the current directory containing the Dockerfile.

Question 7

What is the purpose of a Dockerfile?

Answer 7

A Dockerfile is a script containing a series of instructions on how to build a Docker image.

Question 8

What command is used to start a Docker container?

Answer 8

The command is ‘docker run’.

Question 9

How do you remove a Docker container?

Answer 9

Use the command ‘docker rm container_id’, where ‘container_id’ is the ID of the container you want to remove.

Question 10

What command is used to stop a running Docker container?

Answer 10

The command is ‘docker stop container_id’, where ‘container_id’ is the ID of the running container.

Question 11

How can you view the logs of a Docker container?

Answer 11

Use the command ‘docker logs container_id’.

Question 12

What is Docker Hub?

Answer 12

Docker Hub is a cloud-based repository where Docker users can create, test, store, and distribute container images.

Question 13

How do you pull an image from Docker Hub?

Answer 13

Use the command ‘docker pull image_name’.

Question 14

What is the purpose of the ‘docker-compose up’ command?

Answer 14

The ‘docker-compose up’ command starts and runs the entire application as defined in the ‘docker-compose.yml’ file.

Question 15

How do you share data between Docker containers?

Answer 15

You can share data between Docker containers using Docker volumes.

Question 16

What is a Docker volume?

Answer 16

A Docker volume is a storage mechanism that allows data to persist beyond the lifecycle of a container.

Question 17

How do you create a Docker network?

Answer 17

Use the command ‘docker network create network_name’.

Question 18

What is the purpose of Docker Swarm?

Answer 18

Docker Swarm is a native clustering and orchestration tool for Docker, enabling the management of a cluster of Docker nodes as a single virtual system.

Question 19

How do you update a service in Docker Swarm?

Answer 19

Use the command ‘docker service update service_name’.

Question 20

What is the purpose of the ‘EXPOSE’ instruction in a Dockerfile?

Answer 20

The ‘EXPOSE’ instruction informs Docker that the container listens on the specified network ports at runtime.

Question 21

What is the ‘ENTRYPOINT’ instruction in a Dockerfile?

Answer 21

The ‘ENTRYPOINT’ instruction specifies the command that will run when a container is started from the image.

Question 22

What is the difference between ‘CMD’ and ‘ENTRYPOINT’ in a Dockerfile?

Answer 22

‘CMD’ provides default arguments for the ‘ENTRYPOINT’ instruction, whereas ‘ENTRYPOINT’ defines the main command to run in the container.

Question 23

How do you restart a stopped Docker container?

Answer 23

Use the command ‘docker start container_id’.

Question 24

What command is used to remove a Docker image?

Answer 24

The command is ‘docker rmi image_id’, where ‘image_id’ is the ID of the image you want to remove.

Question 25

How do you list all Docker images on your system?

Answer 25

Use the command ‘docker images’.

Question 26

What is the ‘docker exec’ command used for?

Answer 26

The ‘docker exec’ command is used to run a command in a running container.

Question 27

How can you check the resource usage of Docker containers?

Answer 27

Use the command ‘docker stats’.

Question 28

What is the purpose of the ‘VOLUME’ instruction in a Dockerfile?

Answer 28

The ‘VOLUME’ instruction creates a mount point with the specified path and marks it as holding externally mounted volumes from native host or other containers.

Question 29

How do you preview the details of a Docker container?

Answer 29

Use the command ‘docker inspect container_id’.

Question 30

What is a Docker registry?

Answer 30

A Docker registry is a storage and distribution system for Docker images.

Question 31

How can you limit the memory usage of a Docker container?

Answer 31

Use the ‘–memory’ flag with ‘docker run’, e.g., ‘docker run –memory=512m container_name’.

Question 32

What is the ‘FROM’ instruction in a Dockerfile?

Answer 32

The ‘FROM’ instruction specifies the base image to use for the Docker image being built.

Question 33

What is the use of ‘WORKDIR’ in a Dockerfile?

Answer 33

The ‘WORKDIR’ instruction sets the working directory for any subsequent instructions in the Dockerfile.

Question 34

How do you attach to a running Docker container?

Answer 34

Use the command ‘docker attach container_id’.

Question 35

What is the purpose of the ‘.dockerignore’ file?

Answer 35

The ‘.dockerignore’ file is used to specify files and directories to exclude from the Docker build context, similar to a ‘.gitignore’ file.

Question 36

How do you copy files from the host system to a Docker container?

Answer 36

Use the ‘docker cp’ command, e.g., ‘docker cp host_path container_id:container_path’.

Question 37

What is the ‘LABEL’ instruction in a Dockerfile?

Answer 37

The ‘LABEL’ instruction adds metadata to an image, such as a description, version, or maintainer.

Question 38

How do you rename a Docker container?

Answer 38

Use the command ‘docker rename old_name new_name’.

Question 39

What is Docker’s default network driver?

Answer 39

Docker’s default network driver is ‘bridge’.

Question 40

How do you run a Docker container in the background?

Answer 40

Use the ‘-d’ flag with ‘docker run’, e.g., ‘docker run -d container_name’.