Other Dockerfile Instructions – 03/Oct/2019

Other Dockerfile instructions

• Instructions which we are aware as of now
  • FROM
  • LABEL
  • RUN
  • CMD
  • ENTRYPOINT
  • EXPOSE
• Other instructions
  • WORKDIR: Changes default working directory

  FROM alpine
  WORKDIR bin
  
  # build a image 
  docker image build -t testing:1.0 .
  
  docker container run --name test3 -d testing:1.0 sleep 1d
  docker container exec test3 pwd
  # bin/
  
  Also try tomcat:8
  
  

  • ARG:
    • They are used to set the values while building the image
  • ENV:
    • To set the variable with Value, so that you can use the value while building the image & Change the value if required while container is created.
    • ENV values become environment variables in your Docker container.
  • USER:
    • This will set the USER Name
    • Execute the folllowing instructions & Make a note of Results

  FROM alpine
  
  docker image build -t usertest:1.0
  
  docker container run -d --name test1 usertest:1.0 sleep 1d
  
  docker container exec test1 whoami
  
  FROM alpine
  USER test
  
  docker image build -t usertest:2.0
  
  docker container run -d --name test2 usertest:2.0 sleep 1d
  
  docker container exec test2 whoami
  

Multi Staged Docker Image Building

• Creating optimized Docker images is why we use multi stage builds
• Multi stage builds can be directly integrated with CI/CD