Docker Basics Quiz

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Welcome! 🐳
Test your fundamental Docker knowledge with this quick quiz.

Instructions:

• Select the best answer for each question.
• Your score will be shown at the end.
• Aim for 100% to prove you are ready for the next level!

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Which command is used to run a container from an image?

docker run

docker start

docker create

docker execute

docker run creates and starts a container in one go. docker start is used to start an existing stopped container.

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What is a Docker Image?

A read-only template used to create containers

A running instance of an application

A virtual machine

A connection to the Docker Hub

A Docker Image is an immutable (read-only) template with source code, libraries, and dependencies required to run an application.

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Which file is used to build a Docker image?

Dockerfile

docker-compose.yml

package.json

Makefile

A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image.

#

Which command lists all running containers?

docker ps

docker list

docker run

docker images

docker ps lists running containers. Use docker ps -a to see all containers (including stopped ones).

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How do you stop a running container?

docker stop [container_id]

docker kill [container_id]

docker rm [container_id]

docker exit [container_id]

docker stop gracefully stops the container. docker kill forces it to stop immediately.

#

Which command downloads an image from a registry?

docker pull

docker fetch

docker get

docker download

docker pull downloads a Docker image from a registry (like Docker Hub).

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What does the -d flag do in docker run -d nginx?

Runs the container in detached mode (background)

Deletes the container after running

Runs in debug mode

Disables networking

-d stands for "detached". It runs the container in the background and prints the container ID.

#

Which command removes a stopped container?

docker rm

docker rmi

docker delete

docker clean

docker rm removes containers. docker rmi removes images.

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Which instruction in a Dockerfile sets the base image?

FROM

BASE

IMAGE

START

FROM initializes a new build stage and sets the Base Image for subsequent instructions.

#

Where are Docker images usually stored?

Docker Registry (e.g., Docker Hub)

Git Repository

S3 Bucket

Local Database

Images are stored in a Registry. Docker Hub is the default public registry.

#

Which command builds an image from a Dockerfile in the current directory?

docker build -t my-image .

docker create -t my-image .

docker make -t my-image .

docker compile -t my-image .

docker build builds an image from a Dockerfile. The . specifies the build context (current directory).

#

What is the default name of the Docker configuration file that defines a multi-container application?

docker-compose.yml

Dockerfile

compose.json

docker-config.yaml

docker-compose.yml is the default file used by Docker Compose.

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Which command is used to view the logs of a container?

docker logs [container_id]

docker output [container_id]

docker show [container_id]

docker print [container_id]

docker logs fetches the logs of a container.

#

What does the -v flag do in docker run?

Mounts a volume

Sets verbose mode

Verifies the image

Sets the version

-v or --volume is used to mount a volume (bind mount or named volume) to the container.

#

Which command lists all locally available images?

docker images

docker list images

docker show images

docker ps -i

docker images (or docker image ls) lists the images stored locally.

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How can you execute a command inside a running container?

docker exec -it [container_id] [command]

docker run -it [container_id] [command]

docker attach [container_id]

docker enter [container_id]

docker exec runs a new command in a running container. -it allows interactive access.

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What is a Docker Registry?

A service for storing and distributing Docker images

A configuration file

A container runtime

A network driver

A Docker Registry is a stateless, highly scalable server side application that stores and lets you distribute Docker images.

#

Which command removes an image?

docker rmi

docker rm

docker del

docker erase

docker rmi (remove image) deletes an image from the local store.

#

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

To inform Docker that the container listens on the specified network ports at runtime

To publish the port to the host

To open the firewall

To expose the container code

EXPOSE functions as a type of documentation between the person who builds the image and the person who runs the container. It does not actually publish the port.

#

Which flag automates the cleanup of the container after it exits?

--rm

--clean

--delete

--tmp

The --rm flag automatically removes the container when it exits.

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