Docker Associate Certification

Question 1

What lists all available/configured Docker networks?

Answer 1

docker network ls

Question 2

What performs a Docker service create?

Answer 2

• no volume (–volume or -v)

- –mount [source=/path],target=[path]

Question 3

What is the docker swarm unlock-key --rotate command for?

Answer 3

It performs a key rotation for security on a regular basis.

Question 4

How do you export the image ‘httpd:latest’ to a tar file called ‘httpd-latest.tar’?

Answer 4

docker save -o httpd-latest.tar httpd:latest

Question 5

What is the Docker command to run a ‘hello-world’ image from the default repository?

Answer 5

docker run hello-world

Question 6

What is the command to allow you to log in with the specified username to a remote image repository?

Answer 6

docker login –username=[USERNAME]

Question 7

What is the directive within a Dockerfile that creates a mount point inside instantiated containers that can be used to mount external volumes?

Answer 7

VOLUME

Question 8

What is the command to list all running swarms in your configuration?

Answer 8

docker swarm ls

Question 9

How do you update a previously draining and/or removed node from the swarm cluster?

Answer 9

docker node update –availability active [NODE ID]

from master

Question 10

What command stops a ‘stuck’ or ‘frozen’ container called ‘myweb’?

Answer 10

docker kill myweb

Question 11

What is the command that lists the services running in your swarm cluster?

Answer 11

docker service ls

Question 12

What’s the command to scale the number of instances in your swarm cluster, once the service is already running/deployed?

Answer 12

docker service scale [SERVICE NAME]=[NUMBER]

Question 13

What demotes a ‘master’ or ‘manager’ node to a ‘follower’ node?

Answer 13

docker node demote [NODE ID]

Question 14

What command promotes a ‘follower’ node to ‘master’ or ‘manager’?

Answer 14

docker node promote [NODE ID]

Question 15

How do you create a Docker image from a Dockerfile in the current directory, naming the image ‘myimage:v1’?

Answer 15

docker build -t myimage:v1

Question 16

What is the command to create a new Docker network for containers to use called ‘mynet’?

Answer 16

docker network create –subnet [RANGE] mynet

Question 17

What command stops a running container called ‘myweb’ 10 seconds after executing the request?

Answer 17

docker stop -t 10 myweb

Question 18

How do you find the Docker management token?

Answer 18

docker swarm

- join-token manager (to add another manager, following prompts)

Question 19

What is the command to remove a service from your swarm cluster?

Answer 19

docker service rm [SERVICE NAME]

Question 20

What is the directive in a Dockerfile that indicates the default command to run in instantiated containers unless overridden at launch time?

Answer 20

ENTRYPOINT

Question 21

How do you perform a Docker swarm manager setup?

Answer 21

docker swarm

> init –advertise-addr [ip address of manager]

Question 22

How do you create a service called ‘my_example’ with 4 replicas from the indicated image?

Answer 22

docker service create –name my_example –replicas 4 [IMAGE SERVICE]

Question 23

What do you use to gracefully remove a node from a swarm cluster?

Answer 23

docker swarm leave (on the node to remove)

Question 24

What does the following command do?

docker swarm unlock

Answer 24

Prompts for unlock key

Question 25

What is the command used to initialize ‘swarm mode’?

Answer 25

docker swarm init

Question 26

How do you take a look at the indicated node to determine its status in the cluster (formatted cleanly)?

Answer 26

docker node inspect –pretty [NODE ID] (on the manager)

Question 27

What command provides a ‘human readable’ method of showing the JSON output from inspect commands?

Answer 27

docker node inspect –pretty [nodeID]

Question 28

How do you force a Docker Swarm that has lost majority by forcing a new swarm?

Answer 28

docker swarm init –force-new-cluster –advertise-addr [IP ADDRESS]
(from ONE of the remaining master nodes)

Question 29

What is the command to list the processes running in your swarm cluster?

Answer 29

docker service ps [SERVICE NAME]

Question 30

What returns the status of a Docker Swarm cluster (from the manager node)?

Answer 30

docker node ls

Question 31

What is the command to join an existing swarm as a ‘worker’ node?

Answer 31

docker swarm join –token [token] [IP]:2377

Question 32

What command lists all available Docker networks in your system or swarm cluster?

Answer 32

docker network ls

Question 33

What is the command to initialize a single replica?

Answer 33

docker service create [image]

Question 34

How do you copy an image called ‘httpd’ from the default image repository?

Answer 34

docker pull httpd:latest
OR
docker pull httpd

Question 35

How do you instantiate a container called ‘myweb’, running non-interactively, from an image called ‘httpd:latest’?

Answer 35

docker run -d –name myweb httpd:latest

Question 36

What directive in a Dockerfile that would allow you to install packages to be included with the image during the build process?

Answer 36

RUN

Question 37

How do you display a list of all running containers on the system?

Answer 37

docker ps

Question 38

What command will remove the image called ‘mistake:v1’ from the local system even if there are containers based on it?

Answer 38

docker rmi –force mistake:v1

Question 39

What are the options to create and/or update a service?

Answer 39

• –name [name of service]
• –publish [#:#] (publish indicated ports and map to underlying host - NOTE: bypasses routing mesh)
• –env [var=value] (environment variable published to each worker in the swarm)
• –workdir [directory] (working directory inside the container/service)
• –user [username] (runas the indicated user)
• –network [network name] (can be used to bypass the mesh network for an overlay)
• –replicas [#]
• –publish-add [#] (add port to host/swarm random high port)
• –publish [-p] published=[port],target=[port][/protocol TCP or UDP]
• –secret [filename] (allows the service access to Docker secrets, use this for each secret)

Question 40

What command displays the logs for the specified service in your swarm?

Answer 40

docker service logs [SERVICE NAME]

from the manager

Question 41

What is the command for a new swarm that will be locked on initialisation

Answer 41

docker swarm init –autolock –advertise-addr [ip of manager]

Question 42

What is the output of the following command?

docker volume ls

Answer 42

• Lists created volumes.

- Will propagate on service creation.

Question 43

What is the Docker logging driver sample configuration (daemon.json)?

Answer 43

{
“log-driver”: “syslog”
“log-opts”: {
“labels”: “production_log”,
“env”: “os,customer”
}
}

Question 44

What command determines nodes in a swarm?

Answer 44

docker node ls

Question 45

How do you initialize a Docker Swarm in order to make it ready to add nodes and services?

Answer 45

docker swarm init –advertise-addr [IP ADDRESS]

Question 46

How do you display all Docker containers (running or stopped), but list ONLY the Container IDs and not the associated names?

Answer 46

docker ps -a -q

Question 47

How do you re-initialize the swarm so it does not attempt to reconnect to old nodes?

Answer 47

docker swarm init –force-new-cluster

Question 48

How do you deploy a container application as a service?

Answer 48

docker service create [SERVICE IMAGE]

Question 49

The directive in a Dockerfile that instantiated containers will listen on the indicated port at launch.

Answer 49

EXPOSE

Question 50

What are the options available for the following command?

docker network create

Answer 50

• –driver=overlay
• –subnet=[network/mask]
• –gateway=[IP]
• –ip-range=[subnet/mask] - only good to further divide network from subnet definition

Question 51

How do you set up the docker container inspect [container]?

Answer 51

• grep for ‘IPAddress’ for IP of container
• grep for ‘Ports’ for port mapping information
• –format=”{{.NetworkSettings.Networks.[network driver].IPAddress}}”
  > for container IP

Question 52

What command lists all images installed locally on a system?

Answer 52

docker images

Question 53

How do you remove a ‘down’ node from a swarm cluster?

Answer 53

docker node rm [NODE ID]

on the manager

Question 54

What command will remove a Docker network called ‘mynet’ from the configuration?

Answer 54

docker network rm mynet

Question 55

Information about global service.

Answer 55

• Runs on each active node in the swarm, at least one
• –mode [global] .
• The replica is a default when not indicated OR when replica number is provided.

Question 56

What command stops a running container called ‘myweb’?

Answer 56

docker stop myweb

Question 57

What are the available options for the following command?

docker prune

Answer 57

• –all (-a) - remove unused images (not just dangling)
• –force (-f) - force removal without prompting
• –volumes - prune unused volumes as well (not default)

Question 58

What is the shortcut command to remove all stopped containers?

Answer 58

docker rm docker ps -a -q

Question 59

What performs a Docker service create?

Answer 59

• no volume (–volume or -v)

- –mount [source=/path],target=[path]