1. Overview

Question 1

What is a Dockerfile?

Answer 1

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

Question 2

What is the use of a .dockerignore file?

Answer 2

It allows you to exclude files from the context like a .gitignore file allow you to exclude files from your git repository. It helps to make build faster and lighter by excluding from the context big files or repository that are not used in the build.

Question 3

How do you specify what docker image to use as a template in a Dockerfile?

Answer 3

By using the FROM command.

eg. FROM node

Question 4

How do you specify the work directory to be created in a Dockerfile?

Answer 4

By using the WORKDIR command.

eg. WORKDIR /usr/src/app

Question 5

How do you copy a file or multiple files from the root of the project into the workdir in a Dockerfile?

Answer 5

By using the COPY command.

eg. COPY package*.json ./

Question 6

How do you run an npm command in a Dockerfile?

Answer 6

By using the RUN command.

eg. RUN npm install

Question 7

How do you copy the entire root content of a project into the work directory in a Dockerfile?

Answer 7

By using the COPY command.

eg. COPY . .

Question 8

How do you specify a port to be exposed in a Dockerfile?

Answer 8

By using the EXPOSE command.

eg. EXPOSE 4000

Question 9

How do you specify a default command to be executed in order to run the app in the container in a Dockerfile?

Answer 9

By using the CMD commad.

eg. CMD ["npm", "start"]

Question 10

Can you have more than one CMD commands in a Dockerfile?

Answer 10

No. Only the last CMD will take effect.

Question 11

How do you create a new Docker image using a Dockerfile?

Answer 11

By executing the docker build command after having specified the image name via the -t flag, and the directory that the Dockerfile is in.

eg. docker build -t atlaskaplan/simple-backed .

PS. the dot (.) at the end means that the Dockerfile is in the current directory.

Question 12

How do you list all the Docker images you created alongside their IDs, creation dates, tags, and sizes in the commandline?

Answer 12

By executing the docker images command.

eg. docker images

Question 13

How do you delete a Docker image from your system?

Answer 13

By executing the docker rmi command and specifying the image ID.

eg. docker rmi e30b45e15491

Question 14

How do you run a Docker image?

Answer 14

By executing the docker run command having specified the port using the -p flag and specifying the Docker image’s name.

eg. docker run -p 4000:4000 atlaskaplan/simple-backend

Question 15

How do you stop a running Docker container?

Answer 15

By executing the docker stop command with the Docker container’s ID or name.

eg.

docker stop d56bf8342cfa
OR
docker stop container-name

Question 16

How do you list all Docker containers that are currently running as well as additional information about them in the commandline?

Answer 16

By executing the docker ps command.

eg. docker ps

Question 17

How do you start a docker container?

Answer 17

By executing the docker start command with the Docker container’s ID or name.

eg.

docker start d56bf8342cfa
OR
docker start container-name

Question 18

How do you push a Docker image onto your DockerHub?

Answer 18

By executing the docker push command with the Docker image’s ID or name.

eg.

docker push d56bf8342cfa
OR
docker push container-name

Question 19

How do you pull an image from DockerHub?

Answer 19

By executing the docker pull command with the Docker image’s name.

eg. docker pull node