A Beginner’s Guide to Docker
Docker has rapidly emerged as the technology of choice forpackaging and deploying moderndistributed applications. Its name has become synonymous with containers. But what exactly is Docker, how does it work, and why should you use it? Read on and we’ll explain the key concepts and features of Docker, as well as the benefits it brings to enterprise IT. We’ll also show how you can get the most out of your Docker container environments.
Before we do any of that, let’s first tackle the fundamentals of containers.
Containers 101
If this is totally new territory to you, you’ll likely be asking:What are containers, anyway? Briefly stated, containers are an alternative to the traditionalvirtualizationmethod, which uses virtual machines (VMs) topartitioninfrastructure resources. But where VMs are fully fledged guest operating systems, containers are significantly morestreamlinedoperating environments, which provide only the resources an application actually needs to function. This is made possible due to the way containers areabstractedfrom the host infrastructure. Instead of using a hypervisor to distribute hardware resources, containers share thekernelof the host OS with other containers.
This can significantly lower the infrastructurefootprintof your applications, as containers can package up all the system components you need to run your code without the bloat of a full-blown OS. The reduced size and simplicity of containers also means they canstop and startmore quickly than VMs thus making them moreresponsiveto fluctuating scaling requirements. And unlike a hypervisor, a container engine doesn’t need to emulate an entire OS. Taken as a whole, containers generally offer betterperformancewhen you compare them to more traditional VM deployments.
Containers and the Cloud
Containers are ideally suited to today’scloudapproach to application architecture where, instead of relying on one, large monolithic program, you can break things up into a suite of loosely-coupledmicroservices. This provides you with a number of benefits. For example, you canreplicatemicroservices across a cluster of VMs to improvefault tolerance. Should an individual VM fail, your application can fall back on other microservices in the cluster and continue to function. What’s more, microservices are easier to maintain, as you canpatch or updatethe code and system environment of your containers without affecting others in your cluster.
Containers and DevOps
The compact design of containers makes them highly portable. As a result, with the help ofDevOps tools, such as Jenkins and CodeShip, they’re easy to incorporate intocontinuous integration (CI)andcontinuous delivery (CD)workflows. From a developer standpoint, containers are also highly practical, as they can be hosted ondifferent servers不同的配置,每个提供server OS is using the same Linux kernel or, at least, one that’s compatible with the container environment.
This allows coders to focus on code without needing to worry about the underlying infrastructure on which it will eventually run. Equally, developers can work collaboratively on projects regardless of the host environment each of them may be using.
ShouldYouUse Docker?
Docker is one ofseveraldifferent container platforms. So, why would choose it over other container solutions? Well, first, Docker is, far and away,themost widely usedcontainer service. It’s popularity rests squarely on the fact that it’s a robust, secure, cost-effective, and feature-rich solution that’s easier to deploy than any of its competitors. Second, it’s anopen-source解决方案的s backed by a large community of companies and individuals who are continually contributing to the project. It offersstrong supportand alarge ecosystemof complementary products, service partners, and third-party container images and integrations. Moreover, selecting Docker won’t tie you to a specific vendor.
Finally, the Docker platform allows you to run its containers onWindows. This is made possible by a Linuxvirtualization layer, which sits between the Windows OS and the Docker runtime environment. In addition to Linux container environments, Docker for Windows also supports native Windows containers.
Although alternatives are now gradually maturing, when one looks across the container landscape, Docker still leads the way and remains the best choice for the majority of use cases. But before you decide whether Docker is right for you, here are the key concepts you’ll need to understand in advance of getting started with the Docker platform:
Docker Engine
This is the application you install on your host machine tobuild, run, and manageDocker containers. As the core of the Docker system, it unites all of the platform’s components in a single location.
Docker Daemon
The workhorse of the Docker system, this component listens to and processesAPI requeststo manage the various other aspects of your installation, such as images, containers, and storage volumes.
Docker Client
This is the primaryuser interfacefor communicating with the Docker system. It accepts commands via the command-line interface (CLI) and sends them to the Docker daemon.
Docker Image
A read-onlytemplateused for creating Docker containers. It consists of a series of layers that constitute anall-in-one package, which has all of the installations, dependencies, libraries, processes, and application code necessary to create a fully operational container environment.
Docker Container
A living instance of a Docker image that runs an individualmicroserviceorfull application stack. When you launch a container, you add a top writable layer, known as acontainer layer, to the underlying layers of your Docker image. This is used to store any changes made to the container throughout its runtime.
Docker Registry
Acatalogingsystem for hosting, pushing, and pulling Docker images. You can use your own local registry or one of the many registry services hosted by third parties (e.g., Red Hat Quay, Amazon ECR, Google Container Registry, and the Docker Hub). ADocker registryorganizes images into storage locations, known asrepositories, where each repository contains different versions of a Docker image that share the same image name.
With these fundamentals under your belt, let’s take a brief look at several other aspects of Docker containers about which you should be aware:
Container Orchestration
Once you’re ready to deploy an application to Docker, you’ll need a way toprovision, configure, scale, and monitor你的容器在microservice建筑师ure. Open-source orchestration systems, such as Kubernetes, Mesos, and Docker Swarm, can provide you with the tools you’ll need to manage your container clusters. Typically, these are able to:
- Allocate compute resources between containers
- Add or remove containers in response to application workload
- Manage interactions between containers
- Monitor the health of containers
- Balance the load between microservices
Cost and Performance Optimization
Finally, you’ll need tooptimizeyour deployments to ensure that you’re getting the best performance and efficiency from your containers. Start bystreamliningyour containers as much as possible by packaging only what your application needs. This best practice also helps to minimize theirattack surfaceand, thereby, improve security. And to assure that your containers are making the most efficient use of resources possible, you’ll want to routinelymonitorthem to be certain that they’re maintaining a good balance of CPU and memory allocation, cluster sizing, and replication of microservices. These steps are particularly important in cloud-based deployments because unnecessary resource consumption adds additional and unnecessary costs to your monthly cloud bills.
Learn more about Docker
A Beginner’s Guide to Understanding and Building Docker Images
3 Essential Steps to Securing Your Docker Container Deployments
Published: June 22, 2020
Last updated: June. 22, 2023
