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https://github.com/jwilleke/docker-demo


https://github.com/jwilleke/docker-demo

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README 

        
# Docker Demo



The simplest kind.



Based on [https://www.cherryservers.com/blog/docker-build-command](https://www.cherryservers.com/blog/docker-build-command)



How to build a Docker image from Dockerfile: Step-by-step

To build a Docker image from Dockerfile, let's see the docker build command in action. In the below steps, we will build a simple Docker image, a web server to serve out a web page through installation. You're going to be building, running, and testing it on your local computer.



## Step 1 - Create a working directory



Create a directory or folder to use for this demonstration ("docker-demo" is used here) and navigate to that directory by running the following commands in your terminal:



mkdir docker-demo

cd docker-demo

Create a file called "index.html" in the directory and add the following content to it:



``` html



  

    

    Simple App

  

  

    
Hello World


    
This is running in a docker container


  



```



This will serve as the web page to be served up by the server.



## Step 2 - Select a base image



Next, select a suitable base image from Docker Hub or a local repository. The base image forms the foundation of your custom image and contains the operating system and essential dependencies. Almost every single image for Docker is based on another image. For this demonstration, you'd be using nginx:stable-alpine3.17-slim as the base image.



## Step 3 - Create a Dockerfile



Now create a file named "Dockerfile". This file will define the build instructions for your image. By default, when you run the docker build command, docker searches for the Dockerfile.



## Step 4 - Add build instructions to the Dockerfile



Open the Dockerfile in a text editor and add the following lines:



``` bash

FROM nginx:stable-alpine3.17-slim

COPY index.html /usr/share/nginx/html



EXPOSE 80 

CMD ["nginx", "-g", "daemon off;"]

```



The instruction above will create a Docker image that serves the provided "index.html" file through the Nginx web server when a container is launched based on that image.



The FROM instruction initializes a new build stage and sets the base image for subsequent instructions. The COPY instruction copies files or directories (usually the source code) from the source to the specified location inside the image. It copies the file to the "/usr/share/nginx/html" directory, which is the default location for serving static files in the Nginx web server. The main purpose of the CMD instruction is to provide defaults for executing containers. The instructions defined in Dockerfiles differ based on the kind of image you're trying to build.



## Step 5 - Build the image using the Docker build command



Before building the Docker image, confirm that you have Docker installed by running the docker --version command.



confirm docker install



To build your container, make sure you're in the folder where you have your Dockerfile and run the following command in the terminal:



``` bash

docker build -t dockerdemo:v1 .

```



This command initiates the Docker build process to create a Docker image based on the instructions specified in the Dockerfile located in the current directory (.)



The -t flag specifies a tag for the image, allowing you to assign a name and version to it. In this case, the image will be tagged as "sampleapp" with the version "v1" providing a descriptive identifier for the image, making it easier to reference and manage.



You should see the build process start and an output indicating that it has finished when it is done.



## Step 6 - Verify the built Docker image



After a successful build, verify the image by running the docker images command to list all the available images on your Docker host. You should see your newly created image listed with its assigned tag and other relevant details, ready to be used for running containers or pushing to a container registry for distribution.



``` bash

docker images

```



## Step 7 - Run the Docker image



Next, run the Docker image as a container using:



``` bash

docker run -p 9991:80 aug12018/dockerdemo:latest

```



This command tells Docker to run the sampleapp container. The -p flag specifies the port mapping, which maps a port from the host machine to a port inside the container. Here, you are mapping port 8080 of the host machine to port 80 of the container. You can modify the host port as per your preference. Ensure you specify the image name and version you used when building the image.



## Step 8 - Access the application



With the container running, you can go ahead to access the application. Open a web browser and navigate to  and you should see the sample web page displayed on your web browser.



## Push dockerdemo image to Registry



Tag the image



``` bash

docker tag dockerdemo aug12018/dockerdemo:latest

```



Push the image to Docker Hub

Where:



- aug12018 is the user name for Docker Hub

- latest is the tag which is the build



``` bash

docker login

docker push aug12018/dockerdemo:latest

```



> Note: "aug12018/dockerdemo:latest" is used in [docker-demo-deployment.yaml](./base/docker-demo-deployment.yaml) file.



## Kubernetties Deployment



If you did not clone the repository create the following:



``` bash

mkdir base

cd base

touch docker-demo-deployment.yaml

touch docker-demo-ingress.yaml

cd ..

touch docker-demo-namespace.yaml

touch kustomization.yaml

```



And refer to the github repository to get file contents.



## 21-Apps



[21-Apps docker-demo](https://github.com/jwilleke/21-apps/tree/master/k8s/apps/docker-demo)



``` bash

cp -r kustomize/ /Volumes/docs/jim/data/systems/tower/apps/21-apps/k8s/apps/docker-demo/

```