Docker Guide

Docker

  • Application: Artifact(JAR+WAR) + Environemnt
  • Docker App -> JVM -> OS
  • Docker CLI(Commands) -> Docker Daemon -> OS
  • Create Image -> Docker Image -> OS(Own)

java -jar spring-rest-application.jar -> Makes it run in JVM

  • [OS + Install Java] + JAR file -> Run JAR file Support Team Dev Team
  • Containers : Images which are running
  • Containerzation is better than virtualization

Docker Engine

  • Helps in creating executable images

Docker Client

  • CLI to build, publish, pull, run images
  • Invokes Docker Daemon REST API endpoint for doing the work

Docker Deamon

  • Contains images & containers

Docker Objects

  • Images, Containers/Services, Network, Volume

Docker Registry

  • Stores images(Eg. Docker hub, AWS container registry, google container registry etc.)

Dockerfile

  • Commands to build image

Docker Storage

  • Maintains single copy of shared data
  • Volume(Dir mounted) : Common across container to use the shared data

Docker Compose

  • Multiple containers/services running together

Legacy Way to run an application in OS

  1. Install Windows 10/Centos(Centos OS Size- Virtual OS- LINUX variant of Java)
  2. Install Java 1.8

yum install java(No installer in Linux, so run yum command)

brew install java(In Mac)

  1. Copy JAR file to root path or any specific path
  2. Run JAR(Write in quotes) java -jar spring-rest-application.jar

Docker way to run the application

  1. Create Docker file
  • Example 1 : Centos OS
FROM centos [Centos empty OS]
RUN yum install -y java
VOLUME /tmp [Containers are stateless and data selected each time. So can use the dir specified in volume across containers and when started again or newly]
COPY target/abc.jar abc.jar
ENTRYPOINT["java","-jar","/spring-rest-application.jar"]
  • Example 2 : Alpine OS
FROM alpine:3.2 
RUN apk --update add openjdk8-jre   [apk command instead of yum]
COPY target/abc.jar abc.jar
ENTRYPOINT["java","-jar","/spring-rest-application.jar"]
  • Example 3 : Install Java with Installed OS
FROM openjdk8-jre-slim
WORKDIR /home [Default target path for all throughput. Prefixed in each path]
COPY target/abc.jar abc.jar
EXPOSE 8080
ENTRYPOINT["java","-jar","/spring-rest-application.jar"]
  • Example 4 : catalina base installs tomcat in /usr/local/tomcat
FROM tomcat:latest
add target/sample.war /usr/local/tomcat/webapps/
EXPOSE 8080
cmd["catalina.sh","run"]
  • Create image(-t : Specifies name, . : dockerfile path in current directory, If name not mentioned, then alphanumeric)

docker build -t anu-application:1.0.

  • Check images

docker images

  • Check containers

docker ps

  • Stop containers(Returns container id if stopped successfully)

docker stop container-id

  • Start container

docker start container-id

  • Stop all containers running

docker ps -a

  • Remove all stopped containers

docker container prune

  • Run the images. This runs in centos OS. So, cant be accessed from our OS

docker run anu-application

  • Accessing in localhost[5000 is outside port accessible from localhost]

docker run -p 5000:8080 anu-application

  • Force delete image

docker image rm -f anu-application

  • Debug Container(-it: internative, else detached, exec: run inside docker container, bash: cmd prompt, sh: cmd prompt, ctrl+d: come out of container)

docker exec -it container-name bash

Docker Commands

  • Check version docker -v
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