Dockerfiles

Dockerfile

  • Specify Base Image: FROM name-of-image
  • Define a Working Directory: WORKDIR /nameofdir
    • The name of directory in which the container will execute commands
    • Must be used, CD commands are not persisted across image layers.
  • Copy current directory contents into container at /nameofdir: ADD . /nameofdir
  • Expose a port outside of the container: EXPOSE portnumber
  • Define an environment variable: ENV NAME variable
  • Define Command to Be Run: RUN <linux-command>
  • Add Files to Image: ADD –CHOWN=<user>:<group> <name-of-file-source> <name-of-file-destination>
    • Can also pull from URL
    • Can unpack TAR files
  • Copy Files to Image: COPY –CHOWN=<user>:<group> <name-of-file-source> <name-of-file-destination>
    • Doesn’t have capabilities of ADD named above.
  • Run Command:
    ENTRYPOINT: <name-of-command>
    CMD: <parameters-of-command>
    • Can provide in Exec or Shell Format, former is preferred, uses JSON array.
    • Some choose not to use ENTRYPOINT and put both command and parameters in CMD.
  • Create Image Command: docker image build -t <name-of-image> .
    • Uses the Dockerfile in the current folder.
    • Use .dockerignore file to exclude files from being added to image.