21 - DOCKER

Question 1

How do we isolate services

Answer 1

Install applications on different virtual servers

Question 2

Why we isolate services

Answer 2

To archieve high availability
High performance

Question 3

cons of VM

Answer 3

o Expenditure
o Compute resources

Question 4

what is a container

Answer 4

A standard unit of software that packages up code, dependencies for development, shipment and deployment

Question 5

container vs VM

Answer 5

Container offer isolation not virtualization
Containers are OS virtualization
VM’s are hardware virtualization
VM’s needs OS
Containers don’t need OS
Containers uses host OS for compute resource

Question 6

what is docker

Answer 6

Docker is a container runtime environment, manages containers

Question 7

advantages of docker

Answer 7

Standard and portable
Lightweight
secure

Question 8

docker installation and setup on linux VM

Question 9

add user to docker group

Answer 9

sudo vim /etc/group
docker: x :999:ubuntu
$ usermod -aG ubuntu

Question 10

enable docker start on boot

Answer 10

sudo systemctl enable docker

Question 11

Install hello-world image

Answer 11

docker run hello-world

Question 12

what is dockerhub

Answer 12

Registry for docker images

Question 13

describe a docker image

Answer 13

o A stopped container like vm image
o Consist of multiple layers
o An app will be bundled in an image
o Containers run from images
o Images are called repositories in registries

Question 14

popular docker registries

Answer 14

ECR, GCR, dockerhub

Question 15

command to create/run a container

Answer 15

docker run [image-name]

Question 16

command to view docker images locally

Answer 16

docker images

Question 17

Get image locally

Answer 17

docker pull image_name

Question 18

run container with name in detached mode

Answer 18

docker run –name myweb -d nginx -p [host port]: [container port]

Question 19

list running containers

Answer 19

docker ps

Question 20

list all containers

Answer 20

docker ps -a

Question 21

stop/start a container

Answer 21

docker stop/start [container_id]

Question 22

view container details

Answer 22

du -sh [container_id]

Question 23

run command into container

Answer 23

docker exec myweb /bin/bash
docker exec -it myweb /bin/bash

Question 24

remove image

Answer 24

docker rmi nginx

Question 25

remove container

Answer 25

docker rm [id]

Question 26

view low-level docker logs

Answer 26

docker inspect

Question 27

view docker logs

Answer 27

docker logs container_name

Question 28

run mysql container

Answer 28

docker run -d -P -e MYSQL_ROOT_PASSWORD=mypass mysql:5.7

Question 29

docker persistent data options

Answer 29

volumes and bind mounts

Question 30

sample command for mysql bind mount

Answer 30

docker run - - name vprodb -d -e MYSQL_ROOT_PASSWORD=secretpass
-p 3030:3306 -v /home/ubuntu/vprodbdata:/var/lib/mysql mysql:5.7

Question 31

create docker volume

Answer 31

docker volume create mydbdata

Question 32

what is a docker volume

Answer 32

host machine reference for container storage

Question 33

create docker mysql volume mount

Answer 33

docker run - - name vprodb -d -e MYSQL_ROOT_PASSWORD=secretpass
-p 3030:3306 -v mydbdata:/var/lib/mysql mysql:5.7

Question 34

view volume content

Answer 34

ls /var/lib/docker/volumes/mydbdata

Question 35

what is a dockerfile

Question 36

sample dockerfile

Answer 36

o FROM
o LABELS
o RUN
o ADD/COPY
o CMD
o ENTRYPOINT
o VOLUME
o EXPOSE
o ENV
o USER
o WORKDIR
o ARG
o ONBUILD

Question 37

o Write dockerfile
Image, author, project, install git, install apache2
Start apache in foreground
Port 80
Noninteractive environment
Specify working dir
Create a volume location
Add nano.tar to webserver location
Build image
Run container
Host image to dockerhub
Remove images and containers
Run container from dockerhub

Answer 37

Use an official base image
FROM ubuntu:20.04

Set author metadata
LABEL author=”Your Name”
LABEL project=”Your Project”

Install required packages (git, apache2) and clean up apt cache
RUN apt-get update && \
DEBIAN_FRONTEND=noninteractive apt-get install -y git apache2 && \
apt-get clean && \
rm -rf /var/lib/apt/lists/*

Start Apache in the foreground
CMD [“apache2ctl”, “-D”, “FOREGROUND”]

Expose port 80
EXPOSE 80

Set noninteractive environment
ENV DEBIAN_FRONTEND=noninteractive

Specify working directory
WORKDIR /var/www/html

Create a volume location
VOLUME /var/www/html

Copy nano.tar to the webserver location
COPY nano.tar /var/www/html

Build image using: docker build -t my-apache-image .
# Run container using: docker run -d -p 8080:80 –name my-apache-container my-apache-image

Question 38

usage of CMD

Answer 38

CMD [command, argument]

Question 39

usage of ENTRYPOINT

Answer 39

ENTRYPOINT [command] #
receives command and argument via the command line

Question 40

usage of CMD/ENTRYPOINT

Answer 40

ENTRYPOINT [command]
CMD [argument]

Question 41

what is docker-compose

Answer 41

Docker Compose is a tool for defining and running multi-container Docker applications. It allows you to define an entire application stack, including services, networks, and volumes, in a single YAML file called a docker-compose.yml file. With Docker Compose, you can manage complex, multi-container applications more efficiently by simplifying the process of defining, configuring, and deploying them.

Question 42

docker-compose installation

Answer 42

run curl command
make executable

Question 43

getting started guide

Answer 43

https://docs.docker.com/compose/gettingstarted/

Question 44

build and run containers with docker-compose

Answer 44

docker compose up

Question 45

what is a multistage dockerfile?

Answer 45

A multi-stage Dockerfile is a Dockerfile that uses multiple build stages to create a final Docker image. This technique is especially useful for creating smaller and more efficient Docker images by separating the build and runtime environments. Multi-stage builds allow you to include only the necessary files and dependencies in the final image, discarding unnecessary build tools and artifacts.

Question 46

sample multistage dockerfile