Mastering Docker Minified Systems: A Step-by-Step Guide with Real Use Cases

Introduction

Docker is a powerful platform for developing, shipping, and running applications. Minified Docker systems are optimized for size and efficiency, making them ideal for production environments where resources are at a premium.

Step 1: Understanding Docker Basics

Before diving into minified systems, ensure you have a solid understanding of Docker concepts like images, containers, volumes, and networks.

Key Commands:

docker pull [image_name] # Download an image from Docker Hub
docker run -d --name [container_name] [image_name] # Run a container in detached mode

Step 2: Creating a Minified Dockerfile

A minified Dockerfile contains only the essential layers needed to run your application.

Example Dockerfile:

FROM alpine:latest
RUN apk add --no-cache python3 py3-pip
COPY . /app
WORKDIR /app
RUN pip install -r requirements.txt
CMD ["python3", "app.py"]

Step 3: Building and Running Your Minified Container

Build your image with the Docker build command, tagging it appropriately.

Build Command:

docker build -t my-minified-app .

Step 4: Optimizing Your Image

Use multi-stage builds to reduce size and remove unnecessary build dependencies.

Multi-Stage Dockerfile:

# Build stage
FROM python:3.8-slim as builder
COPY requirements.txt .
RUN pip install --user -r requirements.txt

# Final stage
FROM python:3.8-alpine
COPY --from=builder /root/.local /root/.local
COPY . .
CMD ["python", "./app.py"]

Step 5: Managing Data and State

For stateful applications, use volumes to persist data.

Volume Command:

docker volume create my_volume
docker run -d -v my_volume:/data my-minified-app

Step 6: Networking and Communication

Link containers and enable communication between them using Docker networks.

Network Commands:

docker network create my_network
docker run -d --net=my_network my-minified-app

Step 7: Deploying to Production

Deploy your containerized application using orchestration tools like Docker Swarm or Kubernetes.

Step 8: Monitoring and Maintenance

Monitor your containers and systems using tools like Docker stats, cAdvisor, or Prometheus.

Conclusion

Mastering Docker minified systems involves understanding Docker fundamentals, optimizing Dockerfiles, managing data, and deploying efficiently.

Further Learning

• Docker Official Documentation: docs.docker.com
• Dockerfile Best Practices: Dockerfile Best Practices
• Docker Networking: Docker Networking

Remember, practice makes perfect. Start small, iterate, and gradually incorporate these practices into larger projects.

---

This guide provides a foundational understanding of working with minified Docker systems. For more in-depth learning, refer to the provided links and continue exploring real-world use cases. Happy Dockering!

What is Kubernetes? Container orchestration explained

Docker containers have reshaped the way people think about developing, deploying, and maintaining software. Drawing on the native isolation capabilities of modern operating systems, containers support VM-like separation of concerns, but with far less overhead and far greater flexibility of deployment than hypervisor-based virtual machines.

Containers are so lightweight and flexible, they have given rise to new application architectures. The new approach is to package the different services that constitute an application into separate containers, and to deploy those containers across a cluster of physical or virtual machines. This gives rise to the need for container orchestration—a tool that automates the deployment, management, scaling, networking, and availability of container-based applications.

[ Are you ready for the container invasion? Learn how to get started with Kubernetes. | Kubernetes, Slack, TensorFlow, Vue.js, and more: See InfoWorld’s 2018 Technology of the Year Award winners. | Cut to the key news and issues in cutting-edge enterprise technology with the InfoWorld Daily newsletter. ]

Enter Kubernetes. This open source project spun out of Google automates the process of deploying and managing multi-container applications at scale. While Kubernetes works mainly with Docker, it can also work with any container system that conforms to the Open Container Initiative (OCI) standards for container image formats and runtimes. And because Kubernetes is open source, with relatively few restrictions on how it can be used, it can be used freely by anyone who wants to run containers, most anywhere they want to run them.

Get Docker for Debian Up and Running

Estimated reading time: 9 minutes

To get started with Docker on Debian, make sure you meet the prerequisites, then install Docker.

Prerequisites

Docker EE customers

Docker EE is not supported on Debian. For a list of supported operating systems and distributions for different Docker editions, see Docker variants.

OS requirements

To install Docker, you need the 64-bit version of one of these Debian or Raspbian versions:

• Stretch (testing)
• Jessie 8.0 (LTS) / Raspbian Jessie
• Wheezy 7.7 (LTS)

Docker CE is supported on both x86_64 and armhf architectures for Jessie and Stretch.

Uninstall old versions

Older versions of Docker were called docker or docker-engine. If these are installed, uninstall them:

$ sudo apt-get remove docker docker-engine

It’s OK if apt-get reports that none of these packages are installed.

The contents of /var/lib/docker/, including images, containers, volumes, and networks, are preserved. The Docker CE package is now called docker-ce.

Extra steps for Wheezy 7.7

• You need at least version 3.10 of the Linux kernel. Debian Wheezy ships with version 3.2, so you may need to update the kernel. To check your kernel version:
  
  $ uname -r
• Enable the backports repository. See the Debian documentation.
  

Install Docker CE

You can install Docker CE in different ways, depending on your needs:

• Most users set up Docker’s repositories and install from them, for ease of installation and upgrade tasks. This is the recommended approach.
  
• Some users download the DEB package and install it manually and manage upgrades completely manually. This is useful in situations such as installing Docker on air-gapped systems with no access to the internet.
  

Install using the repository

Before you install Docker CE for the first time on a new host machine, you need to set up the Docker repository. Afterward, you can install and update Docker from the repository.

Set up the repository

1. Install packages to allow apt to use a repository over HTTPS:
   
   Jessie or Stretch:
   
   $ sudo apt-get install \
        apt-transport-https \
        ca-certificates \
        curl \
        gnupg2 \
        software-properties-common
   Wheezy:
   
   $ sudo apt-get install \
        apt-transport-https \
        ca-certificates \
        curl \
        python-software-properties
2. Add Docker’s official GPG key:
   
   $ curl -fsSL https://download.docker.com/linux/debian/gpg | sudo apt-key add -
   Verify that the key ID is 9DC8 5822 9FC7 DD38 854A E2D8 8D81 803C 0EBF CD88.
   
   $ sudo apt-key fingerprint 0EBFCD88
   
   pub   4096R/0EBFCD88 2017-02-22
         Key fingerprint = 9DC8 5822 9FC7 DD38 854A  E2D8 8D81 803C 0EBF CD88
   uid                  Docker Release (CE deb) <docker@docker.com>
   sub   4096R/F273FCD8 2017-02-22
3. Use the following command to set up the stable repository. You always need the stable repository, even if you want to install edge builds as well.
   
   
   Note: The lsb_release -cs sub-command below returns the name of your Debian distribution, such as jessie.
   
   
   
   To also add the edge repository, add edge after stable on the last line of the command.
   
   amd64:
   
   $ sudo add-apt-repository \
      "deb [arch=amd64] https://download.docker.com/linux/debian \
      $(lsb_release -cs) \
      stable"
   armhf:
   
   You can choose between two methods for armhf. You can use the same method as Debian, setting up the repository and using apt-get install, or you can use a convenience script, which requires privileged access, but sets up the repository for you and installs the packages for Bash auto-completion.
   
• Setting up the repository directly:
  
  $ echo "deb [arch=armhf] https://apt.dockerproject.org/repo \
      raspbian-jessie main" | \
      sudo tee /etc/apt/sources.list.d/docker.list
• Using the convenience script:
  
  $ curl -sSL https://get.docker.com > install.sh
  
  $ sudo bash ./install.sh
  
  Warning: Always audit scripts downloaded from the internet before running them locally.
  
  
  
  If you use this method, Docker is installed and starts automatically. Skip to step 4 below.
  
4. Wheezy only: The version of add-apt-repository on Wheezy adds a deb-src repository that does not exist. You need to comment out this repository or running apt-get update will fail. Edit /etc/apt/sources.list. Find the line like the following, and comment it out or remove it:
   
   deb-src [arch=amd64] https://download.docker.com/linux/debian wheezy stable
   Save and exit the file.
   
   Learn about stable and edge channels.
   

Install Docker CE

NOTE: Docker CE is not available on raspbian-jessie, scroll down to follow the Raspian steps.

1. Update the apt package index.
   
   $ sudo apt-get update
2. Install the latest version of Docker, or go to the next step to install a specific version. Any existing installation of Docker is replaced.
   
   Use this command to install the latest version of Docker:
   
   $ sudo apt-get install docker-ce
   
   Warning: If you have multiple Docker repositories enabled, installing or updating without specifying a version in the apt-get install or apt-get update command will always install the highest possible version, which may not be appropriate for your stability needs.
   
   
3. On production systems, you should install a specific version of Docker instead of always using the latest. This output is truncated. List the available versions:
   
   $ apt-cache madison docker-ce
   
   docker-ce | 17.03.0~ce-0~debian-jessie | https://download.docker.com/linux/debian jessie/stable amd64 Packages
   The contents of the list depend upon which repositories are enabled, and will be specific to your version of Debian (indicated by the jessie suffix on the version, in this example). Choose a specific version to install. The second column is the version string. The third column is the repository name, which indicates which repository the package is from and by extension its stability level. To install a specific version, append the version string to the package name and separate them by an equals sign (=):
   
   $ sudo apt-get install docker-ce=<VERSION_STRING>
   The Docker daemon starts automatically.
   
4. Verify that Docker CE is installed correctly by running the hello-world image.
   
   $ sudo docker run hello-world
   This command downloads a test image and runs it in a container. When the container runs, it prints an informational message and exits.
   

Docker CE is installed and running. You need to use sudo to run Docker commands. Continue to Linux postinstall to allow non-privileged users to run Docker commands and for other optional configuration steps.

Upgrade Docker CE

To upgrade Docker, first run sudo apt-get update, then follow the installation instructions, choosing the new version you want to install.

Install on Raspian (Raspberry Pi)

Warning: This isn’t necessary if you used the recommended bash $ curl -sSL https://get.docker.com | sh command!

Once you have added the Docker repo to /etc/apt/sources.list.d/, you should see docker.list if you:

$ ls /etc/apt/sources.list.d/

And the contents of the docker.list should read:

deb [arch=armhf] https://apt.dockerproject.org/repo raspbian-jessie main

If you don’t see that in docker.list, then either comment the line out, or rm the docker.list file.

Once you have verified that you have the correct repository, you may continue installing Docker.

1. Update the apt package index.
   
   $ sudo apt-get update
2. Install the latest version of Docker, or go to the next step to install a specific version. Any existing installation of Docker is replaced.
   
   Use this command to install the latest version of Docker:
   
   $ sudo apt-get install docker
   
   NOTE: By default, Docker on Raspian is Docker Community Edition, so there is no need to specify docker-ce.
   
   
   
   
   NOTE: If bash $ curl -sSL https://get.docker.com | sh isn’t used, then docker won’t have auto-completion! You’ll have to add it manually.
   
   
3. Verify that Docker is installed correctly by running the hello-world image.
   
   $ sudo docker run hypriot/armhf-hello-world
   This command downloads a test image and runs it in a container. When the container runs, it prints an informational message and exits.
   

Install from a package

If you cannot use Docker’s repository to install Docker CE, you can download the .deb file for your release and install it manually. You will need to download a new file each time you want to upgrade Docker.

1. Go to https://download.docker.com/linux/debian/dists/, choose your Debian version, browse to stable/pool/stable/, choose either amd64 or armhf,and download the .deb file for the Docker version you want to install and for your version of Debian.
   
   
   Note: To install an edge package, change the word stable in the URL to edge. Learn about stable and edge channels.
   
   
2. Install Docker CE, changing the path below to the path where you downloaded the Docker package.
   
   $ sudo dpkg -i /path/to/package.deb
   The Docker daemon starts automatically.
   
3. Verify that Docker CE is installed correctly by running the hello-world image.
   
   $ sudo docker run hello-world
   This command downloads a test image and runs it in a container. When the container runs, it prints an informational message and exits.
   

Docker CE is installed and running. You need to use sudo to run Docker commands. Continue to Post-installation steps for Linux to allow non-privileged users to run Docker commands and for other optional configuration steps.

Upgrade Docker

To upgrade Docker, download the newer package file and repeat the installation procedure, pointing to the new file.

Uninstall Docker

1. Uninstall the Docker package:
   
   $ sudo apt-get purge docker-ce
2. Images, containers, volumes, or customized configuration files on your host are not automatically removed. To delete all images, containers, and volumes:
   
   $ sudo rm -rf /var/lib/docker

You must delete any edited configuration files manually.

Next steps

• Continue to Post-installation steps for Linux
  
• Continue with the User Guide.

Source: https://docs.docker.com/engine/installation/linux/debian/#next-steps

Error Faced while using KataCoda while Building Multiple dockers

Today I was doing some online training - Building and testing Multiple Dockers using Katacoda online platform. Ups, I guess I have not explained what Katacoda is ... Ok here is ....

Extracted from Wikipedia:  What is Katacoda ?? 

"A code kata is an exercise in programming which helps a programmer hone their skills through practice and repetition. The term was probably first coined by Dave Thomas, co-author of the book The Pragmatic Programmer,^[1] in a bow to the Japanese concept of kata in the martial arts. As of October 2011, Dave Thomas has published 21 different katas.^[2] "

While practicing some of the tasks in there I have notice docker build failing to build .. Did not resolved myself yet.. I guess I just wen to do a quick investigation and find out what was fundamentally causing the error.

Here is the errors I was getting;

Basically for some reason, I was getting a weird error while building the Go layer ..

So, looking into the dashboard and what I was seeing then, I then realised that the error was on the command to install the Go on the docker .. Did not actually resolved it .. I guess, I just keep a record of it in case of happen again ..

So, as you can see there is a bug on there .. I need to investigate, later on I will publish, what I found out.. My intention is to replicate the build locate and see if I can spot the same error ..

:-)