Docker

   yum install docker
   yum install epel-release -y
   yum install docker-io
   systemctl start docker
   systemctl status docker
   systemctl enable docker
   docker run hello-world
   docker images
   docker info
   docker version
   docker

(one shot easy way, curl -fsSL https://get.docker.com/ | sh systemctl start and enable docker)

  docker pull ubuntu
  docker images
  #docker rmi ubuntu
  docker run ubuntu cat /etc/issue
  #docker run [local image] [command to run into container]
  docker ps -l
  docker start 2201ce5e1124
  docker ps
  docker stop dreamy_mccarthy
  docker ps -l
  docker stop sad_carson
  docker ps -l
  docker ps
  docker run --name myname  ubuntu cat /etc/debian_version
  docker start myname
  docker stats myname
  docker top myname

--------------------------------------------------------------

https://hub.docker.com

example:
docker pull nginx:1.10.2-alpine
docker images
 docker run --name myenginx3 -d -p 82:80 nginx:1.10.2-alpine
 docker ps -a
docker stop myenginx3
 docker ps -a
docker start myenginx3
 docker ps -a
http://localhost/

example:2
docker rm myenginx3

 docker ps -a

login to container--> docker exec -ti myenginx3 /bin/sh
vi /etc/nginx/nginx.conf  (this is inside container )
exit
docker stop myenginx3
docker rm myenginx3
docker run --name myenginx3 -d -v /home/uploads/local.conf:/etc/nginx/nginx.conf:ro -p 82:80 nginx:1.10.2-alpine     (local conf linking to container's conf as ReadOnly)

example:3
docker stop  myenginx3
docker rm  myenginx3
vim /home/uploads/source/index.html --->Hello
docker run --name myenginx3 -d -v /home/uploads/local.conf:/etc/nginx/nginx.conf:ro -v /home/uploads/source:/usr/share/nginx/html:ro -p 82:80 nginx:1.10.2-alpine

Big-example:

vim Dockerfile
FROM nginx:1.10.2-alpine
MAINTAINER hasarangaprasad@gmail.com
COPY ./local.conf /etc/nginx/nginx.conf

same location--> vim local.conf
user  nginx;
worker_processes  1;
error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;

events {
    worker_connections  1024;
}

http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';
    access_log  /var/log/nginx/access.log  main;
    sendfile        on;
    #tcp_nopush     on;
    keepalive_timeout  65;
    gzip  on;

    include /etc/nginx/conf.d/*.conf;
}

docker build -t zip-alpine:1.0 .   (-t means tag, last dot means find docker file in current location )
(docker ps -a, stop and remove current containers )
Lets create container call  thiismyenginx3 using my image.

docker run --name thiismyenginx3 -d -v /home/uploads/source:/usr/share/nginx/html:ro -p 82:80 zip-alpine:1.0

(if u change html /home/uploads/source/index.html , its updating real time without restart container)

----------------------------------------------------

https://www.tecmint.com/install-docker-and-learn-containers-in-centos-rhel-7-6/



=================
=================
jenkins migrate with docker
http://mmorejon.github.io/en/blog/migrate-jenkins-to-a-docker-container/

 vim Dockerfile 

FROM jenkins:latest
MAINTAINER hasarangaprasad@gmail.com
COPY ./jenkins/ /var/jenkins_home/
USER root
RUN chmod -R 777 /var/jenkins_home/

docker build -t myjen:3.0 .
docker run -d -p 8085:8080 --name jentest myjen:3.0
==========
auto restart with VM is starting
use --restart unless-stopped with docker run command


---

Run 2 containers (ex: app and db)



docker pull mysql
docker pull phpmyadmin/phpmyadmin

docker run --name mysql -e MYSQL_ROOT_PASSWORD=0000 -d mysql

1st way to start app. Mannyally say mysql container's docker ip

docker run --name myadmin -e PMA_HOST=172.17.0.2 -e DB_ENV_MYSQL_ROOT_PASSWORD=0000 -d -p 8081:80 phpmyadmin/phpmyadmin


2nd way to start app: without mentioning db host (docker ip) mannualy

docker run --name myadmin -d --link mysql:db -p 8080:80 phpmyadmin/phpmyadmin

--link takes care of automatically adding the linked container to the /etc/hosts file).

This way you do not have to rely on a specific IP address, be it the host's one or whatever.

Notes:
1.check envr variables : docker exec myadmin env

2.login to app gui, enable mysql plain text password as bellow:
docker exec -it mysql bash
mysql -u root -p 
<0000> 
ALTER USER root IDENTIFIED WITH mysql_native_password BY '0000'; 
exit 
exit
Now access <public IP>:8080 and <public IP>:8180

another ex: https://hub.docker.com/r/phpmyadmin/phpmyadmin/

-----
docker-compose
(The easy way --> build image, run container at once for MULTIPLE services)
otherwise we have to use 'link' to connect each other (docker run --name mywpress --link mymysqk:mysql -p 8080:80 -d wordpress)

install : https://docs.docker.com/compose/install/#install-compose

sudo curl -L https://github.com/docker/compose/releases/download/1.21.2/docker-compose-$(uname -s)-$(uname -m) -o /usr/local/bin/docker-compose

sudo chmod +x /usr/local/bin/docker-compose

mkdir /home/folder/

cd /home/folder

vim docker-compose.yml

version: '2'

services:

  wordpress:

    image: wordpress

    ports:

      - 8080:80

    environment:

      WORDPRESS_DB_PASSWORD: abc123

  mysql:

    image: mysql:latest

    environment:

      MYSQL_ROOT_PASSWORD: abc123

/usr/local/bin/docker-compose ps

/usr/local/bin/docker-compose up -d

/usr/local/bin/docker-compose ps

goto---> IP:8080 --> you will see WordPress is connected to mysql and , etc ..




Docker Networking

Overlay: Layer2 communication (without complex NAT's)



============
DEFAULT NETWORKS
docker network ls

OVERLAY NRTWORK

Ingress Network

EMBEDDED DNS

-----------------------------------------------

Docker compose another good example. 

I have spring boot app and database connection properties are in application properties file.

https://drive.google.com/open?id=10qmeHuOZHge7iQdf_6Gdoy1WRcsSMJHT

extract this (Docker file and target folder)   

create docker-compose.yml same location. (application properties (url) are overriding with docker environment variables) 

-------------------------------------------------------------

version: '2'

services:

    db:

      image: mysql:5.7

      container_name: sample_db

      volumes:

        - sample_db:/var/lib/mysql

      restart: always

      environment:

        - MYSQL_ROOT_PASSWORD=password

        - MYSQL_DATABASE=test

        - MYSQL_USER=sa

        - MYSQL_PASSWORD=password

      ports:

        - "3306:3306"

    web:

      build:

        context: ./

        dockerfile: Dockerfile

      image: users-mysql

      environment:

        - spring.datasource.url=jdbc:mysql://db:3306/test

      ports:

          - 8086:8086

      depends_on:

          - db

volumes:

    sample_db: {}

/usr/local/bin/docker-compose -f docker-compose.yml up

------------------------------------------------------------------------------------

https://stackoverflow.com/questions/44790923/docker-compose-spring-boot-postgres-connection

------------------------------------------------------------------------------------

Another one with scaling and load balanced (Same java app is used)

===

version: '2'

services:

  web:

    build:

      context: ./

      dockerfile: Dockerfile

    image: users-mysql

    environment:

      - spring.datasource.url=jdbc:mysql://db:3306/test

    ports:

      - 8080

    links:

      - db

    networks:

      - front-tier

      - back-tier

  db:

    image: mysql:5.7

    restart: always

    environment:

      - MYSQL_ROOT_PASSWORD=password

      - MYSQL_DATABASE=test

      - MYSQL_USER=sa

      - MYSQL_PASSWORD=password

    networks:

      - back-tier

  lb:

    image: dockercloud/haproxy

    ports:

      - 80:80

    links:

      - web

    networks:

      - front-tier

      - back-tier

    volumes:

      - /var/run/docker.sock:/var/run/docker.sock

networks:

  front-tier:

    driver: bridge

  back-tier:

    driver: bridge

===

/usr/local/bin/docker-compose -f docker-compose.yml up -d

/usr/local/bin/docker-compose logs

/usr/local/bin/docker-compose scale web=2

/usr/local/bin/docker-compose logs