DevOps Classroom notes 07/Jan/2024

Dockerfile contd

ADD COPY:

• To copy the files into docker image
• Refer Here for ADD and Refer Here for COPY instructions official docs
• ADD and COPY both copy the files into Docker image where as
  • ADD can copy from local as well remote files into docker image
  • COPY can copy files or folders from local system only
• Refer Here for the changes done to containerize the game of life application

WORKDIR: Default directory when container starts

• Refer Here for official docs
• Lets implement WORKDIR in spring petclinic with /spc
• Refer Here for the changes

USER

• Refer Here for USER instruction.
• Lets run the spring petclinic as non root user Refer Here for the changes done
  

Parametrization

• Dockerfile allows paramterization at two levels
  • while building the image
    • ARG: Refer Here
  • while running the container
    • ENV

Buildtime variables using ARG

• Refer Here for the changes to include build time variables
  
  
• Refer Here for the changes

Envrionmental variables using ENV

• Refer Here for official docs

SHELL FORM and EXEC FORM

• Shell form: write the command directly

ping google.com

• EXEC form: write the command in the following formats

 ["ping", "google.com"]

• Recommendataions
  • RUN use shell form
  • CMD/ENTRYPOINT: use exec form

Exercise

• Give me a command to create a linux user which doesnot asks me questions
  • It should create a user with a home director and shell setup

addgroup -g 1000 spc
adduser -h "/spc" -u 1000 -G spc -s /bin/bash -D spc

• Look into jenkins/jenkins Dockerfile