How to create a image using Dockerfile

Spread the Knowledge

We learnt docker so we can create better docker images using dockerfile?

What is dockerfile?

- a file
- contains instructions
- for writing each layer
- multiple layers == one image

Rule of dockerfile?

  • each line ==== one layer
  • Each layer would be created from a container from the previous layer

Example of Dockerfile


FROM ubuntu
MAINTAINER Rajesh Kumar <rajesh@devopsschool.com?
RUN apt-get update
RUN apt-get install git -y
COPY index.html /opt

FROM ubuntu
MAINTAINER Rajesh Kumar <rajesh@devopsschool.com?
RUN apt-get update
RUN apt-get install git -y
COPY index.html /opt

FROM httpd
MAINTAINER Rajesh Kumar <rajesh@devopsschool.com?
RUN apt-get update
RUN apt-get install git -y
COPY index.html /opt

   15  mkdir dock-image
   16  cd dock-image/
   17  clear
   18  vi dockerfile
   19  touch index.html
   20  docker build -t ub-up-git .
   21  docker images

Lab & Excercise

- https://devopsschool.com/tutorial/docker/dockerfile/dockerfile-example-sample-lab.html

Example of App Dockerfile
# https://github.com/jenkinsci/docker/blob/587b2856cd225bb152c4abeeaaa24934c75aa460/Dockerfile
# https://github.com/tianon/docker-brew-ubuntu-core/blob/50b110c15148c069706b155a60d21ecfcbb59de9/focal/Dockerfile
# https://github.com/docker-library/httpd/blob/6d68525ac47c0474d3d74269b2669104c1d867dd/2.4/Dockerfile

How to set PID1 for the image?
- CMD or ENTRYPOINT

Reference 
- https://devopsschool.com/tutorial/docker/commands/index.html
- $ docker help
Rajesh Kumar
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