DOCKER Notes from Jay Likhare (Github: @JayLikhare316)

#Q.What is Docker? Why we need docker?
A. Docker is a containerization platform that allows developers to package, ship, and run applications in
containers. Containers are lightweight and portable, making it easier to develop, test, and deploy applications.

#Q.What are containers?
A. Containers are a type of virtualization that allows multiple applications to run on a single host operating
system, each with its own isolated environment. Containers share the host operating system, but each container
has its own file system, network stack, and process space.

#Q.Virtualizer vs hypervisor?
A. Hypervisor is a type of virtualization that creates a separate operating system for each virtual machin
(HVM), whereas virtualizer is a type of virtualization that runs on top of a host operating
system and shares the host operating system with the guest operating system (non-HVM).

#Q.Monolythic app vs Microservice app?
A. Monolythic app is a single application that performs multiple functions, whereas microservice app is
a collection of small, independent services that work together to perform a specific function.

#Q.What is port forwarding?
A. Port forwarding is a technique used in networking to forward incoming traffic from one port to another port.
It allows a service running on a specific port on a host to be accessed from outside the host.


#install docker in linux.

enable & start docker
sudo systemctl enable docker
sudo systemctl start docker
sudo ststemctl status docker
sudo docker run -d -p instance-port:container port container name or container ID (-d for detached -p for port forwarding -P for random port forwording)
sudo docker images
sudo docker ps -a --> to see all stopped containers
sudo docker ps
sudo docker run -itd amazonlinux bash
sudo docker exec -it <container_id> /bin/bash --> to go inside the docker shell
cd usr/share/nginx.html/
rm index.html
echo "hello world" > index.html
sudo docker inspect <container_id> --> to inspect docker container
sudo docker logs <container_id> --> to get logs of the container
sudo docker stop <container_id> --> to stop the container
sudo docker start <container_id> --> to start the container
sudo docker rm <container_id> --> to remove the container
sudo docker rmi <image_id> --> to remove the image
sudo docker rmi -f <image_id> --> to remove the image forcefully
sudo docker commit <container_id>
sudo docker image --> to see all images for docker
sudo docker tag <image_id> <new_image_name> --> to tag the image

#login into the docker account in linux

sudo docker login --> to login into the docker
sudo docker push <docker provided name> -->
sudo docker run --name <> -d -P <name of repo>
sudo docker tag demo (username)/(reponame)
sudo docker push (username)/(reponame):latest

#if I want to create my private image you can use ECR

you have to create a ec2 role for ecr <ec2containerregistryfullaccess>
copy login command
aws ecr get-login-password --region <region> --profile <profile> | docker login --username AWS
sudo docker tag <image_id> <account_id>.dkr.ecr.<region>.amazonaws
sudo docker push <account_id>.dkr.ecr.<region>.amazonaws/<image_name>
sudo docker pull <account_id>.dkr.ecr.<region>.amazonaws/<image_name>

task:-
task1)
# get the docker image of amazon linux
sudo docker pull amazonlinux
sudo docker exec run -itd -p 80:8080 amazonlinux
# add tomcat package
# add student ui
# then commit the image -->container se image banana
# store on ecr as well as docker hub

task2)

# get the docker image of amazon linux
# install nginx
# add free css

task3)

# host mysql container
# -e (enviornment variables)
# use msql user/mysql password

30 dec 2024--

task4)
#make a deamon service of tomcat.

#docker container storage
#persistane

# docker config files
etc/docker
docker volumes:-

docker create volume --> to create docker volume (universal docker storage)
docker volume ls --> to list volumes
cd var/lib/docker --> root directory of docker
/var/run/docker.sock --> docker socket file

# Q.what is socket file?
# A.socket file is a file that allows two processes to communicate with each other.

sudo docker run -d -v dev:usr/share/nginx/html -P nginx --> to add volume to the container
sudo -v for volume dev for volume name :path to mount volume --name --> for adding name to container

# DOCKERFILE:-

# dockerfile is a text file that contains instructions for building a docker image.
# docker file is a step by step instruction to our docker image.

# dockerfile commands:-

1. FROM:- it is used to specify the base image for our image.
2. RUN:- it is used to run a command in the container.
3. COPY:- it is used to copy a file from the local machine to the container.
4. ADD:- it is used to copy a file from the local machine to the container.
5. WORKDIR:- it is used to set the working directory in the container.
6. EXPOSE:- it is used to specify the port that the container will listen on.
7. ENV:- it is used to set an environment variable in the container.
8. VOLUME:- it is used to specify a directory in the container that will be persisted ev
9. CMD:- it is used to specify the default command to run when the container is started.
10. ENTRYPOINT:- it is used to specify the default command to run when the container is started
11. USER:- it is used to specify the user that the container will run as.
12. ONBUILD:- it is used to specify a command that will be run when the image is
13. ARG:- it is used to specify a variable that can be passed to the dockerfile.
14. LABEL:- it is used to specify a label that can be used to identify the image.

>>> demofile:

FROM nginx
COPY boxer-html /usr/share/nginx/html

vim dockerfile --> paste above to dockerfile
docker build -t dockerfile

##
FROM amazonlinux
RUN yum update && yum install -y nginx
EXPOSE 80
CMD ["usr/sbin/nginx", "-g" , "daemon off;"]

vim dockerfile --> paste above to dockerfile
sudo docker build -t dummy-nginx
sudo run -it dummy-nginx bash

##
FROM amazonlinux
RUN yum update && yum install java-17 -y
COPY . .
RUN chmod 777 apache-tomcat-10.1.34/bin/catalina.sh
EXPOSE 8080
CMD ["apache-tomcat-10.1.34/bin/catalina.sh", "run"]

##task-

Q.Difference between entrypoint and cmd?
cmd is used to specify the default command to run when the container is started.
entrypoint is used to specify the default command to run when the container is started.

## docker (tomcat with studentui)

FROM amazonlinux
RUN yum update && yum install -y java-17 && yum install maven -y
COPY tomcat /tomcat/.
RUN chmod 777 tomcat/bin/catalina.sh
EXPOSE 8080
COPY student-ui /student-ui/.
WORKDIR /student-ui
RUN mvn clean package
RUN mv target/*.war /tomcat/webapps/student.war
CMD ["/tomcat/bin/catalina.sh", "run"]

## #multistage docker file:(from docker container {dockerhub})

FROM maven:3.9.9-amazoncorrectto-debian-bookwarm AS builder --> #maven ko builder ka naam de diya
COPY student-ui
RUN mvn clean package
FROM tomcat:jre8-alpine
COPY --from=builder /target/*.war webapps/student.war

what is multistage dockerfile?

multistage dockerfile is a feature of docker that allows you to build multiple images from a single
dockerfile. This is useful when you want to create a smaller final image, but you need to
perform some operations in a larger image.

## Docker 3D architecture:-

what is docker compose?

docker compose is a tool for defining and running multi-container docker applications.
with docker compose, you can define a docker application using a single configuration file,
and then run it using a single command.

sudo docker file name --> docker-compose.yml
sudo docker-compose up --> to start the containers
sudo docker-compose up -d --> to start the containers in detached mode i.e. in background
sudo docker-compose down --> to stop the containers

## Docker Network (By default we use bridge network)

Bridge network:- it is the default network in docker. It is used to connect containers to the host machine.
Host network:- it is used to connect a container to the host machine's network.
None network:- it is used to isolate a container from the host machine's network.
macvlan network:- it is used to assign a mac address to a container.
overlay network:- it is used to connect multiple docker hosts together.


Q. 172.16.0.0/16 --> default ip used by docker.why? {because it is uncommon ip, nobody uses it, thats why}

A. Docker uses the 172.16.0.0/16 ip range by default because it is
a private ip range that is not routable on the internet. This
means that containers running on a host can communicate with
each other using these ip addresses, but they will not be
accessible from outside the host.

# Docker compose file:-

version : '3'
services:
    app:       ##given name of project
    image: nginx
    ports:
        - "80:80"
    volumes:
        - myvolume:/usr/share/nginx/html/      ##givennameof volume : path to be mounted on
    web:
        image: httpd
        ports:
            - "8080:80"
    tomcat:
        image: tomcat:8.5-jdk8-alpine
        ports:
            - "8081:8080"
volumes:
    myvolume:

##how to run docker-compose file
docker-compose up -d   ##-d means detached mode


what is docker network ?

# Types of network in docker ?

why does docker use 172.16.0.0/16 ip ?
aws vpc default network ip is 172.31.0.0/16