DEV Community: Samuel Nzubechi

🧑🏽‍💻Containers and Containerization in DevOps🔥

Samuel Nzubechi — Tue, 01 Aug 2023 01:09:34 +0000

In this tutorial you will learn and discover the power of containers. Learn how they ensure environment consistency, enabling smooth deployment from development to production environments,Differences and between VMs and containers,and many more. Let's revolutionize your DevOps workflow with containers.
Let's go! 🎉🤓

In software development, two effective methods of bundling an application with its environment and dependencies are containers and virtual machines (VMs). Both approaches aim to minimize differences between development and production environments, enabling seamless application deployment.

Containers: Containers use containerization technology, with Docker being the most popular containerization platform. They package applications along with their dependencies, libraries, and configurations, creating isolated and portable units. Containers share the same host operating system kernel, which makes them lightweight and resource-efficient. This shared kernel facilitates faster startup times and better performance. Containers are perfect for deploying microservices-based applications and are a fundamental building block in the cloud-native ecosystem.
Virtual Machines (VMs): Virtual machines, on the other hand, offer a different approach. They create virtualized instances of a complete operating system, including the application and all its dependencies. VMs provide stronger isolation between applications, as each VM runs its own separate kernel. While this isolation comes with some overhead in terms of resource consumption and slower startup times, VMs are highly versatile and can run a broader range of applications and operating systems.

Both containers and VMs are capable of horizontal scaling, meaning you can replicate instances to handle increased traffic or demand. This scalability is crucial for modern applications that need to adapt to varying workloads.

It's important to note that while containers and VMs offer similar benefits in terms of environment consistency and scalability, they differ significantly in their architecture and use cases. In the next page, you'll delve deeper into virtual machines, exploring their unique characteristics and how they contrast with containers.

What is a container? 🧐

A container is a self-contained and isolated unit that encapsulates an application along with all its required dependencies and the necessary runtime environment to run the application. It leverages operating system-level virtualization to enable the execution of multiple isolated processes concurrently.
The key components of a container include:

Application Code: The container holds the application's code, which includes all the files and binaries required to run the application successfully.
Dependencies: Containers package all the dependencies necessary for the application to function correctly. These dependencies typically include libraries, utilities, configuration files, and any other supporting files required by the application.
Runtime Environment: The container includes the runtime environment needed to execute the application. This environment ensures that the application runs consistently across different systems and environments, regardless of variations in the underlying host system.

Benefits of Containers😋🤩

The benefits of using containers are manifold, revolutionizing the way applications are developed, deployed, and run. Here are some key advantages of containers:

Portability: Containers provide an efficient and consistent way to package applications and their dependencies, making it easier for developers to move applications between different environments, such as development, testing, and production. This portability ensures that the application behaves consistently across various hardware and platforms, reducing the risk of issues caused by environment discrepancies.
Isolation and Efficiency: Containers offer lightweight and isolated execution environments for applications. Each container shares the same host operating system kernel, which allows for better resource utilization and less system overhead compared to traditional virtual machines. This efficiency results in faster startup times and better performance for applications running in containers.
Simplified Development and Deployment: Containers streamline the development process by bundling all the necessary components into a single package. This reduces the likelihood of "it works on my machine" issues, as developers can create applications in a controlled and consistent environment. Deployment becomes more straightforward and predictable, as the same container used in development can be deployed to production without modification.
Scalability: Containers facilitate horizontal scaling, allowing applications to handle varying workloads by replicating instances of the container across multiple nodes or servers. With container orchestration platforms like Kubernetes, scaling applications becomes automated and flexible, responding to changing demand effortlessly.
Resource Utilization: Containers enable higher resource density on a single host, making better use of available hardware resources. This ability to run multiple containers on a single machine contributes to cost efficiency and maximizes server utilization.
Version Control and Rollbacks: Containers can be versioned, allowing developers to maintain a history of changes to the application and its dependencies. If an issue arises after deployment, it's easy to roll back to a previous version, ensuring the stability and reliability of the application.
DevOps Collaboration: Containers bridge the gap between development and operations teams. Developers package applications and dependencies into containers, and operations teams can then deploy and manage these containers consistently across different environments, promoting collaboration and reducing deployment-related conflicts.

How to create Containers? 🧑‍🔧

Containers can be created using various container runtime/engines, each offering unique features and functionalities. Some of the well-known container runtime/engines include:

Docker: Widely recognized for its standardized packaging format, Docker simplifies container creation, distribution, and management for diverse applications.
CRI-O: Designed as a lightweight container runtime specifically for Kubernetes, CRI-O optimizes container execution within Kubernetes clusters.
OpenVZ: An open-source container-based virtualization solution, OpenVZ provides isolation for Linux-based containers.
Containerd: Focused on simplicity, robustness, and portability, Containerd serves as a container runtime that can work alongside higher-level container platforms.
Rkt: Tailored for cloud-native environments, Rkt emphasizes application containerization and modern production capabilities.
LXC and LXD: LXC facilitates a vendor-neutral environment for Linux container development, while LXD manages and enhances the user experience with Linux containers.

Docker is the most popular one and hence, in my next article, you will learn to create containers using the Docker engine.😎 🥳

Now let's learn more about the differences between containers and VMs.

What is a VM?🧐

A Virtual Machine (VM) is comparable to a complete computer, functioning with its own operating system and virtualized hardware. Like containers, a host machine can run multiple VMs to scale isolated applications effectively. However, VMs require significant resources since they virtualize an entire machine, making them somewhat resource-intensive. This is where containers present a compelling advantage.

When managing multiple VMs on a host machine, each VM operates with its independent operating system. The host OS oversees these VMs using a hypervisor, specialized software responsible for creating and managing the VMs while ensuring their isolation from each other.
Conversely, containers package an application along with its dependencies, without requiring a separate OS or virtualized hardware. Instead, containers share the underlying host operating system kernel. In practice, a container manager takes care of managing the containers, serving a role akin to that of a hypervisor in the VM scenario.

In essence, VMs offer strong isolation, simulating complete machines but come with higher resource overhead. On the other hand, containers leverage shared resources and lightweight isolation, making them more efficient and agile. Containers' streamlined approach significantly simplifies the management and scaling of applications, making them an increasingly preferred solution in modern software development and deployment scenarios.

How to create VMs? 🧑‍🔧

To set up Virtual Machines (VMs), you can utilize specialized software known as Hypervisors. These Hypervisors allow you to create complete computers, each with its own operating system and virtualized hardware. Here are some popular Hypervisors you can use locally:

Each Hypervisor comes with its unique features, allowing you to create and manage VMs tailored to your needs. However, in this course, we won't dive into the specifics and various types of Hypervisors, as it goes beyond our current scope.

Additionally, if you prefer a cloud-based approach, leading cloud service providers like AWS, GCP, and Azure offer Infrastructure as a Service (IaaS) options. They allow you to create VMs on their cloud infrastructure, providing flexibility, scalability, and ease of management.

Though the details of VM creation are not covered in this tutorial, it's crucial to grasp the relative distinctions between containers and VMs. Containers offer lightweight, efficient, and consistent application packaging, sharing a single host operating system kernel. VMs, on the other hand, virtualize complete machines with their independent OS, providing strong isolation but potentially consuming more resources.

Understanding these differences will help you make informed decisions on when to use containers or VMs, depending on your specific application requirements and deployment scenarios.

Problems with VMs 😔💔

As we've explored before, a Virtual Machine (VM) functions like a self-contained computer, operating with its individual copy of an operating system and virtual hardware. While VMs effectively scale applications, their drawback lies in their resource-intensive nature since they replicate an entire machine virtually. However, there is a more efficient alternative for scaling up your applications – containers.

Containers offer a significant improvement over VMs in terms of resource utilization and scalability. Unlike VMs, containers don't require a complete OS or virtualized hardware. Instead, they bundle an application together with its dependencies, sharing the host operating system kernel. This lightweight approach reduces resource overhead and accelerates performance, making containers a preferred choice when scaling applications.

By leveraging containers, you can achieve a streamlined and more agile deployment process. The ability to rapidly create, distribute, and manage containers empowers developers to scale applications effortlessly without the resource burdens associated with traditional VMs.

In summary, containers offer an efficient and powerful solution for application scaling, making them an ideal choice when you seek to optimize resource usage and enhance your development and deployment workflows.

Summary: Benefits of using Containers versus VMs 📌👌🏽

In comparing Containers to Virtual Machines (VMs), we find several compelling benefits that containers offer:

Size: Containers are significantly smaller in size compared to VMs. While VMs can occupy several gigabytes of storage, containers are typically in the megabytes range. This reduced size makes it easier to store, transfer, and deploy containers efficiently.
Speed: VMs can be relatively slow to start up and may take minutes to launch fully. In contrast, containers boast impressive speed and responsiveness, often launching in a matter of seconds. This rapid startup time allows for quicker application deployment and scalability.
Composability: Containers are designed with a focus on programmable creation, defined as source code. They can be built, deployed, and managed programmatically, promoting a more flexible and automated approach to application development and deployment. In contrast, VMs often replicate conventional computer systems, leading to less agility in certain scenarios.

In essence, containers present a more lightweight, nimble, and programmable alternative to VMs. Their compact size, speedy boot times, and composability make them an attractive choice for modern software development and deployment, particularly when seeking rapid scalability and streamlined workflows.

Let's wrap it up 🎁

In this tutorial, you discovered the power of containers, ensuring environment consistency for smooth deployment from development to production. You learned the differences between VMs and containers, and how containers revolutionize your DevOps workflow. Let containers be your key to faster, more efficient, and scalable software development.

Happy Coding and Thank you for reading! 🎉!

🔥Concepts of Docker🧑‍💻

Samuel Nzubechi — Sat, 20 Aug 2022 14:44:00 +0000

firstly before we dive into docker I'll like you to view my article about containers if you have a little knowlegde concercerning containerization.

In this tutorial you will understand Docker,installation,its core concepts and how it revolutionizes software development. Learn container creation, Dockerfiles, image building, and container management. Discover how Docker ensures consistent environments from development to production. Get ready to elevate your development skills with Docker!

What is Docker?🧐

Docker is a widely acclaimed open-source container runtime tool that revolutionizes the way we build, test, and run containers. It serves as both a container system and a prominent company, leading the containerization movement.

As a container system, Docker enables developers to package applications and their dependencies into a standardized, lightweight, and portable unit called a container. These containers ensure consistent performance across various environments, from development to production, eliminating the "it works on my machine" conundrum. Docker simplifies the deployment process, making it seamless and efficient.

Beyond being a technology, Docker is also the name of the company that played a pivotal role in popularizing containerization. The company's contributions have had a profound impact on software development and DevOps practices, empowering teams worldwide to embrace containers for scalable and agile application deployment.
Docker revolutionizes software development with containerization, isolating applications and dependencies in Docker Images. These images run as portable and lightweight Docker Containers, ensuring consistent execution. The "Dockerfile" defines image creation instructions, and Docker Hub offers a repository for sharing pre-built images. Docker Compose simplifies managing multi-container applications, while Container Orchestration tools like Kubernetes enable scaling and management. Docker's networking and volume features enhance communication and data persistence. Master these fundamental Docker concepts for efficient and scalable application development.

Using Docker, you can create containers with both Linux and Windows kernels, although Windows containers are only available if you are running a Windows machine. In either case (Linux/Windows), you will have to install Docker on your local machine. *Installing Docker means installing * Docker Desktop, a command-line utility.

How to install Docker Desktop? 🧑‍🔧

Installing Docker means installing Docker Desktop, a command-line utility. There are installers available for all the major operating systems: Linux, OSX, and Windows. You can find installers at either of the below links which are part of the official Docker documentation:

Get Docker
Docker Desktop Overview
Once docker is installed you should be able to continue!

1. Docker for Mac

Upon clicking on either of the links above, you will be redirected to Docker Desktop for Mac page.
The requirement is that your macOS must be version 10.14 or newer. This page also has the installation instructions available for you.

Succcessful Installation of Docker Desktop on Mac

2. Docker for Windows 10 Professional or Enterprise (64-bit)

Click on one of the provided links, which will take you to the Docker Desktop installation page for Windows . Make sure to check the System Requirements listed there to ensure compatibility.
Once on the Docker Desktop page, click on the download link for the .exe installer.
After the download is complete, run the .exe file with Administrator privileges.
Follow the prompts to complete the installation process.
During the installation, pay attention to the Configuration page. It is crucial to select the "Enable Hyper-V Windows Features" option, as Docker on Windows relies on Hyper-V for container virtualization.

By following these steps, you will successfully install Docker Desktop on your Windows 10 Professional or Enterprise system. Docker Desktop provides an intuitive interface for managing and running containers on your Windows machine, enabling you to utilize the power of containerization in your development workflow.

3. Docker for Windows 11/10 Home (64-bit)

If you are using Windows 11/10 Home, the process of installing Docker Desktop involves an additional step. Before installing Docker, you must first install and enable the Windows Subsystem for Linux (WSL) 2. This is necessary to ensure that Docker runs smoothly on your system.
To install WSL2, you can refer to the Appendix page for detailed instructions. Once WSL2 is set up on your machine, you can proceed with the regular Docker installation process.
Visit the Docker Desktop for Windows page and download the .exe installer. After the download is complete, run the .exe file as an Administrator. Follow the on-screen prompts to complete the Docker Desktop installation.
During the installation, remember to check the "Enable Hyper-V Windows Features" option on the Configuration page. This step is crucial as Docker relies on Hyper-V for container virtualization.

By installing WSL2 and Docker Desktop, you will unlock the full potential of containerization on your Windows 10 Home machine. Embrace the power of Docker to build, test, and run containers effortlessly, enhancing your software development experience.

Importantly, ensure to check the "Enable WSL 2 Features" option on the Configuration page.

Restart your machine allowing the Docker Desktop to take effect, and launch the WSL from the Start menu.

4. Verify the Docker installation

You can run either of the following commands in your Mac terminal / WSL terminal:

# to check the version
docker version
# to verify that Docker can pull and run images (we will talk more about images next)
docker run hello-world

Verify using docker run hello-world in your Mac terminal

Now let's dive into the Concepts of Docker!🤩

Docker Architecture

The Docker architecture is a well-structured and flexible system that empowers containerization. At its core is the Docker Daemon (dockerd), the engine running on the host system. It manages Docker objects like images, containers, networks, and volumes, ensuring proper isolation and resource utilization. Users interact with the Docker Daemon through the Docker Client (docker), a command-line interface (CLI) tool. Docker Images serve as read-only templates, containing the application code, dependencies, and configurations necessary to run an application. Running instances of these images are called Docker Containers, offering isolated and efficient runtime environments. Docker Registries store Docker Images, with Docker Hub being the primary public repository. Docker provides built-in networking capabilities and Docker Volumes for data persistence. Docker Compose simplifies managing multi-container applications using a YAML file, and Docker Swarm facilitates container clustering and orchestration for scalability and high availability. The comprehensive Docker architecture streamlines the development, deployment, and management of containerized applications, revolutionizing modern software development workflows.

Let's go deeper!😃🤓
1. Docker Engine
The heart of Docker is the Docker Engine, a powerful application comprising three essential components: the Docker daemon, an API, and a client.

The Docker daemon operates as a server, responsible for managing various aspects such as images, containers, networks, and volumes. On the other hand, the Docker client serves as the user interface, facilitating interactions with Docker through the command line. Most of your Docker-related tasks will be executed at the command line using this CLI client.

The Docker client communicates with the Docker daemon through a command line API, creating a seamless bridge between user commands and the daemon's functionality. This communication ensures that users can easily manage Docker resources, create and run containers, and perform other operations efficiently.

2. Docker Image
A Docker image is the set of instructions for creating a container. The image typically includes a file system and the parameters that will be used for the container.

Images are comprised of multiple layers. Each layer contains specific software.

You can create a custom Docker image for a specific application. Start with a standardized parent image as the base layer. The parent image often contains the file system of a particular operating system, such as Ubuntu 18.04. Then add an additional layer to the image, on top of the base layer. You can add your application files to this additional layer. You can even add multiple additional layers, and distribute your application files across different layers, as appropriate for your needs.

3. Docker Container
Docker container is just the Docker-specific implementation of the concept. In practice, Docker containers are created from Docker images - a container is a runnable instance of an image. Note that since the image is a set of instructions for creating a container, multiple containers can be created from the same image.

4. Docker Registries
Docker registries are essential components of the Docker ecosystem, serving as repositories for storing, sharing, and distributing Docker Images. They play a critical role in the containerization process, allowing users to access pre-built images, collaborate with others, and manage private images securely.

How does it work? 🧑🏼‍💻 👨🏼‍💻

Let me give you an overview of the flow of execution for creating a container:

Dockerfile → Docker Image → Docker container

1. Write a Dockerfile 🧑🏼‍💻

It is a text document that contains the commands a user would execute on the command line to assemble an image. In this file, you can specify the necessary environments and dependencies. For example, see a Dockerfile below:

# Pull the "tomcat" image. The community maintains this image. 
FROM tomcat 
# Copy all files present in the current folder to the "/usr/local/tomcat/webapps"  folder 
COPY ./*.* /usr/local/tomcat/webapps

In the example above, every time you create a container, it will have the tomcat web server installed. In addition, all the contents of the current directory will also be copied to the /usr/local/tomcat/webapps folder of each container.

1.Build an Image: 🧑🏼‍💻

Use the docker build command to build an image from the Dockerfile. Usually, we execute this command from the same directory where the Dockerfile is present.

# This command will look for a Dockerfile in the `pwd`, and create myImage
docker build  --tag myImage  [OPTIONS] path_where_to_store_the_image

You can store your images online at DockerHub as well, so that you/anyone can "pull" them on any other machine, anytime. We can even use the pre-created Docker images maintained by the community. e.g docker pull tomcat:latest

2. Create and run a Container

After creating an image, you can use it to create as many Containers as you want on any platform. Each container will have the same environment and dependencies to run a copy of your application. The following command creates and runs a new container: docker run --name myContainer myImage

Let's wrap it up 🎁

In this tutorial , you’ve learned about Docker, which is the most common container platform. You’ve also learnt it's installation, introduced to concepts related to how Docker works, including the

Docker daemon,

Docker client,

Docker images and containers, and

the Docker Registry.