EXAMPLES: Dockerfile MultiStage file

Docker MultiStage file

THIS IS UNI STAGE DOCKER FILE

Step1:-
Download a sample git maven project for this example

    git clone https://github.com/onlineTrainingguy/jenkinscicd.git

Step2:-

go to jenkinscicd dir

    cd jenkinscicd

Step3:-

Modify Dockerfile content as given below

    FROM maven:latest
    WORKDIR /
    COPY src /src
    COPY pom.xml /
    RUN mvn clean package
    CMD java -cp /target/myproj-1.0-SNAPSHOT.jar com.raman.App


Step4:-
Build the image using docker build command

    docker build . -t unistagemavenimg

Step 5:-
Check the image size it will approximate 700 MB+

    docker images unistagemavenimg

Step 6:-
Create container with above image and check the output

    docker run -it unistagemavenimg

output will be
Maven Job is running on Build Server! (but if you following this steps, you will get a different output. why? because in jenkinscicd/src/main/java/com/raman/App.java, the app.java file has a different output. you can check by vi into it and even edit it to your liking!)



Now lets create multi stage Docker file
Step 1: Modify Dockerfile content as given below (notice the AS build)

    FROM maven:latest AS build
    WORKDIR /

    #copy from localfile system to docker file system
    COPY src /src
    COPY pom.xml /
    RUN mvn clean package

    #(if above Dockerfile haven't been run before, include below as well) 

    CMD java -cp /target/myproj-1.0-SNAPSHOT.jar com.raman.App

    FROM openjdk:alpine
    COPY --from=build /target/myproj-1.0-SNAPSHOT.jar /myproj-1.0-SNAPSHOT.jar
    EXPOSE 8080
    CMD java -cp /myproj-1.0-SNAPSHOT.jar com.raman.App


Step 2:- Build image using docker build command

docker build . -t multistageimg

Step 3:- Check the image size it will approximate 100 MB

docker images multistageimg

Step 4:-Create container with above image and check the output

docker run multistageimg

output will be same but the image size is reduced
Maven Job is running on Build Server!