Docker

Question 1

What are challenges that docker resolves?

Answer 1

1) Compatibility
2) Dependencies

Question 2

How to check docker version?

Answer 2

docker version

Question 3

Run hub.docker.com/whalesay

Answer 3

run docker.com/whalesay cowsay Boo

Question 4

List all running containers

Answer 4

ps

Question 5

Show all containers

Answer 5

ps -a

Question 6

Stop running container

Answer 6

stop

Question 7

Remove container permanently

Answer 7

rm

Question 8

List all container images

Answer 8

images

Question 9

Remove docker image

Answer 9

rmi (all dependent containers are removed)

Question 10

Pull image without running a container

Answer 10

pull

Question 11

Why is container in ‘exited’ state?

Answer 11

Container is run when underlying process is run, otherwise is not

Question 12

Run sleep cmd on ubuntu

Answer 12

docker run ubuntu sleep 5

Question 13

Execute a cmd on a running container

Answer 13

exec name-or-id cat /etc/hosts

Question 14

Run in attached mode

Answer 14

run domain\centos

Question 15

Run in detached mode

Answer 15

1) -d
2) run -d domain/centos

Question 16

Attach container

Answer 16

attach name-id

Question 17

What is difference between attached & detached container?

Answer 17

1) Attached: currently loaded to shell prompt
2) Detached: running in the background, not currently loaded to shell

Question 18

Specify which version of a container to run with a TAG

Answer 18

docker run Ubuntu:17.04

Question 19

Flag to run c7s in interactive mode

Answer 19

1) -i
2) docker run -i domain/centos

Question 20

Flag to map host port to c7s port & run

Answer 20

1) -p host-port:c7s-port
2) docker run -p 80:5000 domain\centos

Question 21

How to map a volume

Answer 21

1) -v host-dir:c7s-dir
2) docker run -v /opt/datadir:/var/lib/mysql mysql

Question 22

Flags to run interactive & pseudo-TTY

Answer 22

docker run -it domain/centos

Question 23

Map local port to port of container

Answer 23

docker run -p 80:5000 domain/centos

Question 24

Get container info in JSON

Answer 24

docker inspect

Question 25

Access container log

Answer 25

docker log name-or-id

Question 26

Run c7 selected version with additional cmd

Answer 26

docker run ubuntu:17.10 cat /etc/*release*

Question 27

What is a limiation of running container with specified cmd?

Answer 27

Lack of control of current terminal session until cmd stops

Question 28

How to run background cmd in a container? (detached)

Answer 28

docker run -d ubuntu sleep 15

Question 29

How to go back (attach) to currently run container?

Answer 29

docker attach

Question 30

Forward port & map a volume to a container

Answer 30

run -p 8080:8080 -v /root/dir:var/dir centos

Question 31

Map a volume to a container with credentials (& port map)

Answer 31

run -p 8080:8080 -v /root/dir:var/dir -u root centos

Question 32

Create local image based on Dockerfile with tag

Answer 32

docker build Dockerfile -t domain/centos

Question 33

Make image available on docker-hub

Answer 33

docker push domain/centos

Question 34

How is Dockerfile structured?

Answer 34

INSTRUCTION argument

Question 35

What is first required Dockerfile instruction?

Answer 35

FROM

Question 36

Get access to container history

Answer 36

docker history domain/centos

Question 37

Build docker image from Dockerfile located in current dir

Answer 37

docker build .

Question 38

Build docker image with specified tag-name

Answer 38

docker build . -t my-simple-webapp

Question 39

Tag for push to docker-hub purposes

Answer 39

docker build . -t domain/app-name

Question 40

Login to docker account in terminal

Answer 40

docker login

Question 41

Run simple docker web-app with environment variable

Answer 41

1) -e docker run -e APP_color=blue simple-web-app-color

Question 42

How to find ENV:VAR on a running docker

Answer 42

1) docker inspect 2) Config

Question 43

Example of creating ENV:VAR in Python

Answer 43

color = os.environ.get('APP_COLOR')

Question 44

Examples of CMD usage

Answer 44

1) CMD command param1 = CMD sleep5 2) CMD ["command", "param1"] or CMD ["sleep", "5"]

Question 45

Entrypoint instruction

Answer 45

ENTRYPOINT ["sleep"]

Question 46

How to use default instruction for entrypoint? It can be override

Answer 46

1) ENTRYPOINT ["sleep"] 2) CMD ["5"]

Question 47

What are components of docker engine?

Answer 47

1) Daemon 2) REST API 3) CLI

Question 48

Access docker by remote commands

Answer 48

1) -H=name:port 2) docker -H=remote-docker-engine:2375

Question 49

What are components of docker namespace?

Answer 49

1) InterProcess 2) Mount 3) Network 4) Process ID 5) Unix Timesharing

Question 50

What tools restricts amount of HW resources allocated to a container?

Answer 50

cgroups

Question 51

Cmd to limit cpu usage to 50%

Answer 51

docker run --cpus=.5 centos

Question 52

Cmd to limit memory usage to 100mb

Answer 52

run --memory=100m centos

Question 53

Where docker stores data in linux FS?

Answer 53

/var/lib/docker

Question 54

What architecture is docker based on?

Answer 54

Layered architecture

Question 55

Components of layered architecture

Answer 55

1) OS 2) APT / YUM 3) PIP 4) Source code 5) Entrypoint + 6) Container layer (R/W)

Question 56

Create docker volume dir

Answer 56

docker volume create data_volume

Question 57

Mount volume inside a container

Answer 57

run -v /source-dir:/var/lib/mysql mysql

Question 58

Where are docker volumes created?

Answer 58

/var/lib/docker/volumes

Question 59

Examples of two syntaxes for volume mounting (1)

Answer 59

docker run -v /data/mysql:/var/lib/mysql mysql

Question 60

How docker chooses storage drivers?

Answer 60

Automatically based on OS type

Question 61

What networks are created automatically in docker?

Answer 61

1) Bridge (default) 2) none 3) host

Question 62

List all networks

Answer 62

docker network ls

Question 63

What network feature comes by default with docker? Runs at 127.0.0.11

Answer 63

Embedded DNS

Question 64

What is docker registry?

Answer 64

Central repository of all docker images

Question 65

What is default docker registry?

Answer 65

docker.io

Question 66

What is more secure registry option to use?

Answer 66

Private registry

Question 67

Deploy private registry

Answer 67

docker run -d -p 5000:5000 --name registry regsitry:2

Question 68

Examples of two syntaxes for volume mounting (2)

Answer 68

1) \ --mount 2) run \ --mount type=bind,source=/data/mysql,target=/var/lib/mysql mysql