What Is Docker: A Complete Guide

If your app got popular, you practiced good load balancing by setting up a second server to ensure the application wouldn’t crash from too much traffic. The following command runs an ubuntu container, attaches interactively to your
local command-line session, and runs /bin/bash. A Dockerfile contains the set of instructions for building a Docker Image. For AWS, it’s EC2, GCP has Compute Engine, and Azure has Azure Virtual Machines. Without standardised containers, cargo was often stored haphazardly in the holds of ships or in dockyards. This inefficient use of space meant that ships were not carrying as much cargo as they could potentially hold, leading to higher transportation costs.

what is docker used for

Since containers are only layers upon layers of changes, each new command you create in a Docker image will create a new layer in the container. Still related to savings, a single medium-sized VM can run about 3 to 8 containers. It depends on how many resources your containers use and how much of the underlying OS it needs to boot before running the whole application. That’s exactly the problem Docker and containers solve in general.

What is Docker?

Docker speeds artificial intelligence and machine learning development with fast, easy, portable application development, accelerating innovation and time to market. Also, Docker Hub is home to hundreds of AL/ML images that further support AL/ML development teams. In 2023, Docker launched Docker AI12, which offers developers context-specific, automated guidance when they are editing a Dockerfile or Docker Compose file.

Docker Compose, a tool for defining and running multi-container Docker applications, further streamlines the CI/CD process. It enables developers to explain a complex application’s environment using a YAML file, ensuring the same environment is consistently replicated across all pipeline stages. In modern software development, the microservices approach involves breaking down an application into a suite of more minor, interconnected services. Each service runs its process and communicates with others via lightweight mechanisms, often through an HTTP-based API. Moreover, the Docker service plays a crucial role in this process. It allows the deployment and management of containers at scale, enabling developers to run multiple containers simultaneously.

Docker Hub

Imagine you need to build multiple shipping containers to transport items all over the world. You start with a document listing out the requirements for your shipping container. Containers are designed to isolate applications and their dependencies, ensuring that they can run consistently across different environments. Whether the application is running from your computer or in the cloud, the application behaviour remains the same. Additionally, Docker Swarm, an orchestration tool within the Docker ecosystem, strengthens DevOps practices by automating the deployment and scaling of applications. This automation is vital for achieving faster and more reliable software releases, reducing the potential for human error, and accelerating the rolling process of new features or updates.

what is docker used for

It has its own syntax and defines what steps Docker will take to build your container. Some languages, like Go, allow you to build an image with only the compiled binary and nothing else. This means the Docker container will have much less to load and therefore will use fewer resources. This way you can spin up more containers per VM and use your hardware more efficiently. This way Docker can check if a layer has changed when building an image and decide whether to rebuild it, saving a lot of time.

The Docker daemon

It’s another tool in your toolbox that allows you to code a docker-compose.yml file which describes your environment. First, start a new project in a directory of your choosing, and run npm init -y to create a new package.json file. On the same directory as the Dockerfile, Docker daemon will start building the image and packaging it so you can use it. Docker didn’t add much to the container runtimes at the time – the greatest contribution from Docker to the container ecosystem was the awareness.

what is docker used for

Throughout this article, we have explored how Docker technology revolutionizes the deployment and management of applications. Docker enables an unparalleled level of efficiency and flexibility in software development. With Docker Desktop, the user-friendly interface for managing Docker containers, you can replicate production environments directly on your local machines. This replication includes the exact setup of operating systems, libraries, and even specific versions of software, all within Docker containers.

Running more workloads on the same hardware

A Docker container is a packaged collection of all the app’s libraries and dependencies already prebuilt and ready to be executed. Also, all layers are hashed, which means Docker can cache those layers and optimize build times for layers that didn’t docker what is it change across builds. You won’t need to rebuild and re-copy all the files if the COPY step hasn’t changed, which greatly reduces the amount of time spent in build processes. Finally, in 2020, Docker became the worldwide choice for containers.

If you want to dig deeper into layers, this article gives a lot of detail on how to find, list, and manage them. Jails were the first solution to expand the uses of chroot to allow not only the segregation at the filesystem level, but also virtualizing users, network, sub-systems and so on. This solution was called jails, and it was one of the first real attempts to isolate stuff at the process level. Jails allowed any FreeBSD users to partition the system into several independent, smaller systems (which are called jails).

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Containers enable multiple application components to share the resources of a single instance of the host operating system. This sharing is similar to how a hypervisor allows multiple virtual machines (VMs) to share a single hardware server’s central processing unit (CPU), memory and other resources. This is the physical machine that is used to create the virtual machines. This allows multiple virtual machines, each with their own operating systems (OS), to run on a single physical server. Docker Compose is a tool to simplify the management of complex, multi-container applications in both development and production environments. Using a YAML file to define services, networks, and volumes streamlines the complexities of orchestrating multiple containers.

Check out our comprehensive Docker cheat sheet to learn all the most essential commands to use. By the end of this guide, you’ll have hands-on experience using Docker Desktop
and a better understanding of the benefits of containerizing your applications. You can better understand Docker images by thinking about them as blueprints. They contain snapshots of what a container will include when it runs. Developing applications often involves managing complex databases, programming languages, frameworks, dependencies, and more. Plus, you may face compatibility problems when working with different Operating Systems (OSs).

Components

This command lists out all the Docker Images that are present on your Docker Host. We can restart the container either by specifying the first few unique characters of its container ID or by specifying its name. Whereas in this example, Docker will stop the container named elated_franklin.

  • One of Kubernetes’ standout roles is its capacity to automate various aspects of container management, surpassing the capabilities of traditional Linux commands and manual container handling.
  • If you want to build a web server image, for example, you can include Ubuntu Linux at first.
  • Developers can also use Docker Compose to define persistent volumes for storage, specify base nodes and document and configure service dependencies.
  • Using Docker, developers can build, test, and deploy their applications locally or on a production server.
  • This unit, or container, includes the application’s coding and dependencies so that it can easily run on any computing environment.

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