Steps to build a Docker image using Dockerfile

Dockerfile is a text file that contains instructions. Each instruction builds a layer, so the content of each instruction describes how the layer should be built.

Dockerfile supports the Shell-like command line-ending method of adding "\" at the end of the line and the comment format of "#" at the beginning of the line.

Note when using Dockerfile to build a Docker image:

(1) Try to select a basic system image that meets your needs but is smaller;

(2) Clean up temporary files such as compiled files and installation package cache;

(3) When installing each software, specify the exact version number and avoid introducing unnecessary dependencies;

(4). Add a .dockerignore file or use a clean working directory.

Common instructions for Dockerfile:

(1).FROM: used to specify the base image to be built, which is usually the first instruction in the Dockerfile;

(2) LABEL: used to add labels to help organize images, record license information, assist in automated builds, etc. Labels are key-value pairs stored as strings;

(3). RUN: used to execute commands in the image, which will create a new image layer. Each RUN instruction creates a new image layer, and always combines apt-get update and apt-get install into one RUN;

The RUN instruction has two formats:

A. Shell format: RUN <command>, just like the command entered directly in the command line;

B.exec format: RUN ["executable file", "parameter 1", "parameter 2"];

(4) COPY: supports simple copying of local files into the container. The COPY instruction is usually used to assign application code to the image.

(5).EXPOSE: used to record the network ports used by the application;

(6).ENTRYPOINT: used to specify the program that runs by default after the image is started in container mode;

(7).ENV: Updates the PATH environment variable for programs installed in the container.

The following Dockerfile is used to compile and execute directly in the container https://github.com/fengbingchun/Messy_Test:

FROM ubuntu:16.04
LABEL maintainer="FengBingchun [email protected]" \ 
   version="1.0" \
   description="dockerfile test"
RUN dep_items='git cmake g++-5' \
  && apt-get update \
  && apt-get install -y $dep_items \ 
  && ln -s /usr/bin/g++-5 /usr/bin/g++ \
  && rm -rf /var/lib/apt/lists/*

Build the image. After executing the following command, an image named fengbingchun/ubuntu:16.04 will be successfully generated:

docker build -t fengbingchun/ubuntu:16.04 .

By mounting the host directory, create a new container test and execute the following command:

docker run -it -P --name test --mount type=bind,source=e:\GitCode\docker,target=/home/fengbingchun fengbingchun/ubuntu:16.04 /bin/bash

Then, in the container, cd to the /home/fengbingchun directory, clone Messy_Test and execute the following command:

git clone https://github.com/fengbingchun/Messy_Test

Then cd to the cd Messy_Test/prj/linux_cmake_CppBaseTest directory and execute the following commands in sequence

./build.sh
./build/CppBaseTest

The execution result is shown in the figure below, indicating that the image built by Dockerfile can compile and execute Messy_Test normally:

Save the image fengbingchun/ubuntu:16.04 to a tarball and execute the following command:

docker save -o ubuntu_16.04.tar fengbingchun/ubuntu:16.04

Copy ubuntu_16.04.tar to the Ubuntu system, load an image from the tarball, and execute the following command:

docker load -i ubuntu_16.04.tar

Then perform similar operations on Windows, compile and execute Messy_Test in the newly created container test, and execute the following commands in sequence:

docker run -it -P --name test --mount type=bind,source=/home/xxxx/Disk/GitHub/docker,target=/home/fengbingchun fengbingchun/ubuntu:16.04 /bin/bash
cd /home/fengbingchun/
git clone https://github.com/fengbingchun/Messy_Test
cd Messy_Test/prj/linux_cmake_CppBaseTest/
./build.sh
./build/CppBaseTest

The execution result is shown in the figure below: It shows that after the image generated on Windows is packaged, it can be used normally after loading on Ubuntu.

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