DevOps Classroom notes 12/Sep/2026

Docker arguments

• arguments will be used to modified values at build time

ARG java_version=17
ARG mvn_command="clean test"

FROM ubuntu:latest

ARG java_version=17
ARG mvn_command="clean test"

ARG WORKDIR=/home/ubuntu/

RUN mvn ${mvn_command}

RUN apt-get update && apt-get install openjdk-${java_version}-jdk -y

build docker image and arg value

docker build  --build-arg java_version=21 --build-arg mvn_command="clean package" -t javabase:latest .

keypoints:

• arg values existing during the runtime only (inside Dokcerfile only)
• we can use desfult values or we can change wile buid image --build-arg
• any build instruction you can add arguments
• use build time only arg. if need runtime need use ENV.

Labels:

• labels are key value pairs (metadat) (image details maintainer, projectname, application name )

adding label to Dockerfile

FROM ubuntu 

LABEL key=value

LABEL app_version=1.0

LABEL author=ramjagadeesh

LABEL project=devops

most common labels using org

• mainatainer=devops-platform
• version=1.0.0
• description=“used for java applications”
• team_name=“platform”

LABEL  mainatainer=devops-platform \
       version=1.0.0 \
       description="used for java applications"\
       team_name="platform"

Add label at run time

docker run -dit --name nginx --label enviromet=dev nginx:latest

validate or inspect labels from conatiner

docker inspect --format='{{json .Config.Labels}}' nginx

out put

{"enviromet":"dev","maintainer":"NGINX Docker Maintainers <docker-maint@nginx.com>"}

Task

using spring-petclinic & nopCommerce

1. create Docker image with using args, env, labels a. use common lables b. use arg for packages like java, maven other installtion c. add env like java path , jar files name , app version …etc
2. run container do the inspect get lables, env, args