Beforehand, please install Docker on your machine. If you use macOS, I highly recommend using Docker for Mac1 version (my term is native version) instead of docker-machine because I’m using native version to demonstrate. In case you might wonder why, please read here.

Step 1 - Preparing

A Dockerfile which is a set of instructions to make an image. Dockerfile syntax2 isn’t complicated so I put mine to demonstrate and explain thorough comments.

I start with ubuntu 16:04

FROM ubuntu:16.04

Installing my desire components like

RUN apt-get update && \
    apt-get install -y --force-yes --no-install-recommends\
    apt-transport-https \
    ssh-client \
    build-essential \
    curl \
    ca-certificates \
    git \
    libicu-dev \
    'libicu[0-9][0-9].*' \
    lsb-release \
    python-all \
    rlwrap \
    apt-utils \
    build-essential \
    libssl-dev \
    curl \
    graphicsmagick --fix-missing \
    imagemagick --fix-missing \
    git \
    telnet

Making a default executable for my image with CMD3

CMD ["bash"]

Step 2 - Run it

What you need to do next is to change directory as same level as Dockerfile and run docker build -t demo . then you can check docker images to see your demo image is there.

What I Learnt

Finding instructions to build an image is usually annoying because some lines in Dockerfile may occur errors and a trial consumes time. To understand, suppose my Dockerfile had 3 lines, I observed an error had happened at last line. Obviously, I would have to fix, run and wait. As I mentioned, emotion is problematic hence I think about acceleration.

The fact is Docker caches preceding layers4 so I do follow suggestions from the best docker practices. But I want more than that so I have an idea which I will build on a correct images. It means I break Dockerfile into parts, for lines from beginning don’t cause error will be a correct one, rest of lines are on working Dockerfile. These parts have been connected by FROM my_image:previous_correct

For instance, correct part is

FROM ubuntu:16.04
RUN apt-get update && apt-get install -y

then I build and name it as based image docker build -t mine:based .. Next I just focus on working part like

FROM mine:based
RUN apt-get install ... # line may get error

Eventually, everything is correct, I’m able to make a single final file.

Another thing, inside container of Ubuntu:16.04, you’re not to use sudo at begining5, example RUN apt-get update && apt-get install -y

References


Bryan Nguyễn

Full Stack-Over-Flow Engineer