DevOps Classroom notes 17/Sep/2026

Docker Multi-stage

• A multi-stage build have a single dockerfile with more then one from instruction.
• last from will be main image
• alas name for stages
• multiple stages will suppourted
• --copy-files to main image.
• it will be reduce my docker image size

what problem its sloved

1. one fat image:

• it will contains all packages and build tools and logs , testcases …etc
• everything in single image

2. Build pattern (multiple docker files)

• Dockerfile.build : install pre-requests and build code

• cp required files to local or remote

• copy above files to new docker image (Dockerfile)

• java ==> amazoncorretto (os amazon linux2)

• alpine ==> linux kernerl light weight os

Ex:

git clone https://github.com/spring-projects/spring-petclinic.git

FROM ubuntu AS source-code 

WORKDIR app

RUN git clone https://github.com/spring-projects/spring-petclinic.git

FROM maven:3.8.3-openjdk-17 AS builder

COPY  --from=source-code app/spring-petclinic spring-petclinic

WORKDIR spring-petclinic

RUN mvn clean package -DskipTests

FROM openjdk:17.0.2-jdk AS prod

ENV JAVA_HOME=/usr/jvm/openjdk-17-jdk/bin/

WORKDIR app

COPY --from=builder spring-petclinic/target/*.jar app.jar

COPY --from=source-code app/spring-petclinic/pom.xml pom.xml

CMD ["java", "-jar", "app.jar"]

Task:

1. create multistage build for nop
2. refer here manuall steps
3. refer_source_code