Docker contd

Dockerfile

• Dockerfile has instructions to build a docker image

FROM

• This helps in selecting a base image
• Experiments
  • Exploring options of FROM
  • choosing different base images

Experiment 1

• Lets just add FROM statement in Dockerfile

FROM eclipse-temurin:17-jdk

• pull the base image docker image pull eclipse-temurin:17-jdk and verify images docker image ls
  
• Now lets build image
  
• Now lets add metadata

FROM eclipse-temurin:17-jdk
LABEL author="khaja"

• There is a base image called as scratch which is empty
• Platforms:
  • amd
  • arm
    

RUN

• Run instruction executes the command during image building
• Consider the following Dockerfile

FROM ubuntu:24.04
LABEL author="khaja"
LABEL project="classroom"
RUN apt update &&
    apt install openjdk-17-jdk -y

ADD or COPY

• ADD can copy files from local as well as web into docker image
• COPY can copy the local files or folders into docker image
• Sample Dockerfile

FROM ubuntu:24.04
LABEL author="khaja"
LABEL project="classroom"
RUN apt update && \
    apt install openjdk-17-jdk -y

ADD https://referenceappslt.s3.ap-south-1.amazonaws.com/spring-petclinic-3.3.0-SNAPSHOT.jar /spring-petclinic-3.3.0-SNAPSHOT.jar

ENTRYPOINT/CMD

• This is used to start the application

Note

• Remove all images docker image rm -f $(docker image ls -q)
• When we create a container, container searches for start up command (CMD) if not found searches in base image startup
• container is running as long as startup command is in running state