Docker

Question 1

What is a Docker Image?

Answer 1

A Docker Image is a file which contains all the necessary dependency and configurations which are required to run an application.

Question 2

What is a Docker Container?

Answer 2

A Docker Container is essentially a running instance of an image.

Question 3

Are Docker containers created with a UUID?

Answer 3

Yes, when the container is created a UUID is created. The UUID can be used to help identify the container.

Question 4

What happens when you do not specify a name for a container?

Answer 4

Docker will supply a randomly generated name from two words joined together by an underscore

Question 5

How do you add a name to a Docker container?

Answer 5

You can add –name to your command

Question 6

What does the number to the left a port mapping signify?

Answer 6

The port that the host machine is listening on

Question 7

What does the number to the right a port mapping signify?

Answer 7

The port that the container is listening on

Question 8

What is the benefit of running a container in the foreground mode?

Answer 8

You will be able to all of the output from the container

Question 9

Is foreground or detached mode default for a container?

Answer 9

Foreground is default for a container

Question 10

What command lists all running containers?

Answer 10

docker ps

Question 11

What command lists all containers running or otherwise?

Answer 11

docker ps -a

Question 12

How do you stop a container by name?

Answer 12

docker container stop <image_name></image_name>

Question 13

How do you list all containers within the environment?

Answer 13

docker container ls -aq

Question 14

How would you stop all containers with one command?

Answer 14

docker container stop $(docker container ls -aq)

Question 15

How would you remove a container?

Answer 15

docker container rm <image_name></image_name>

Question 16

How would you remove all containers with one command?

Answer 16

docker container rm $(docker container ls -aq)

Question 17

How do you interactively run a command on a running container?

Answer 17

docker container exec -it <image_name> <command></command></image_name>

Question 18

Can you run the docker container exec command if the primary process is running?

Answer 18

No

Question 19

What does the command docker container start docker-exec do?

Answer 19

Starts the primary process for an exited container

Question 20

What does the -i flag stand for as in:
docker container exec -i

Answer 20

Interactive flag that keeps stdin open

Question 21

What does the -t flag stand for as in:
docker container exec -t

Answer 21

Allocates a pseudo-TTY

Question 22

How do you override the default container command?

Answer 22

Add the command you want to run after docker container run -d <image> <command></command></image>

After the pid 1 process completes, the container will exit

Question 23

Do Docker containers restart when they exit or when the docker daemon is restarted?

Answer 23

No

Question 24

How do you specify a restart policy

Answer 24

Add the –restart flag with the docker run command

Question 25

How do you restart the container if it exits due to an error, which manifests as a non-zero exit code?

Answer 25

Add the –restart on-failure with the docker run command

Question 26

How do you restart the container unless it is explicitly stopped or Docker itself is stopped or restarted?

Answer 26

Add the –restart unless-stopped with the docker run command

Question 27

How do you always restart the container if it stops?

Answer 27

Add the –restart always with the docker run command

Question 28

What is the default restart policy?

Answer 28

–restart no

Question 29

How do you remove a stopped container?

Answer 29

docker rm <container_name></container_name>

Question 30

How do you remove a running container?

Answer 30

docker rm -f <container_name></container_name>

Question 31

How do you see overall disk metrics related to all images, containers, local volumes, and build cache?

Answer 31

docker system df

Question 32

How do you see the container that is using the greatest amount of disk space?

Answer 32

docker system df -v

Question 33

How do you see image space usage?

Answer 33

docker system df -v

Question 34

How do you see containers space usage?

Answer 34

docker system df -v

Question 35

How do you see local volumes space usage?

Answer 35

docker system df -v

Question 36

How do you see build cache usage?

Answer 36

docker system df -v