What is docker?
This is an open-source containerization platform that developers use to package applications into containers. The platform makes it safer, easier and simpler to build and manage containers.
Using automation and simple commands through a single API, developers can build, deploy an update and even stop containers.
What is a container?
This is a package of software that contain all elements it needs to run. They virtualize the Operating System and it can run anywhere, from a private or public cloud to even a personal computer. While they started as a Linux technology they can now be created on windows Os.
How a docker container works
It consists of the following:
This is a special file system that contains some configuration needed for running. Additionally, it provides the registry, program, and resources required to run containers. Since it does not contain any dynamic data, its contents don’t change after its built.
It is an isolated and secure platform. Docker uses them to run applications.
- Image registry
Docker images are stored here after an image is created it’s stored in the registry, which can be public or private. When later needed it’s just downloaded from the registry.
Features of Docker containers
They start quickly and only require a small number of resources. Multiple containers running on one host machine can share the operating system kernel of the machine.
They can run on both Linux and Windows machines and infrastructures including bare metal servers, VMs, and clouds.
- Secure and reliable
It isolates by default and decouples applications from their underlying infrastructures. In a faulty application, only its container is affected. The host machine is not affected.
Docker containerization best practices
We will further subdivide these best practices into five groups namely:
Docker containerization best practices for migrating applications into containers.
As time goes by, your application will need more scaling and your development will move from the traditional applications to microservices and you will essentially need containerization.
Containerization of an already existing application will need different considerations as compared to building a containerized app from scratch. Let’s look at the best practices for containerization of migrating applications.
- Have a long-term vision
A clear and long-term vision is paramount as the teams will focus more on innovation to avoid challenges later.
- Select the right migration strategy
The three main strategies for migration are lift and shift, rewrite, and augment. Teams migrating from monolithic applications achieve a “lift and shift” as they move from an on-premises model to a cloud. Selection of the right strategy is very important. Because an application consists of smaller units, to make the migration and containerization rapid and smoother, they should be packaged into something easily consumable.
- Consider decomposing part of the older applications first
The recent applications are easier to update and even maintain than the older ones. Which may bring the temptation of moving them first. However, decomposing older application parts that are causing pain in operations and later deploying the newer services as containers will be a better idea. This is because you will not have to revamp the entire application.
Docker containerization best practices for building containers.
Below are some of the best practices for building containers:
- A single application per container
Since containers have the same lifecycles as the applications they host, every single application should be in its container. So that the app starts when the containers start and stop when it stops.
- Consider starting with stateless applications
Stateless apps are fantastic at horizontal scaling which is an advantage for modern apps. A stateless backend will remove the possibility of mutable states and long-running connections that make deployment of apps easy and with zero downtime
- Plan for monitoring from the start
Although they are difficult to monitor, monitoring is essential in ensuring the availability, performance, and security of the workloads. A comprehensive approach is therefore needed to ensure greater visibility to provide remedies to problems before they reach users.
Docker containerization best practices for creating container images.
An image is central to containerized architecture.
Docker container images can be built in 3 ways commit, Docker file, and compose.
Best practices for creating container images include:
- Keep container images smaller and simpler
Keeping the images small helps to load them quickly into memory. To keep the image small one should;
- Begin with an appropriate base image.
- Use multistage build.
- Minimize the separate Run commands in the Docker file.
- Smartly tag your images
Tagging helps in managing docker images of different versions since each tag conveys information on a specific image variant.
- Take advantage of the Docker Registry
Users can locally pull and store new images in the registry. The docker register is highly scalable and distributes and stores docker images.
Docker containerization best practices for operating containers.
Find some of the best practices for operating containers below:
- Use persistent data storage
These are storage databases that remain available beyond the life of a container. Persistent volumes should be used so that data can be accessed even when a container is down.
- Employ CI/CD
Continuous integration /Continuous delivery frees you from redeploying everything and manual testing. When employed together with containerization it brings more benefits and flexibility to the entire process.
- Empower with container orchestration tools
Orchestration tools help to control the complexity introduced by containers. They automate deployment, scheduling, scaling, health monitoring, networking, and container management.
Docker containerization best practices for ensuring container security
Some best practices to ensure container security are:
- Protect container runtime
This can be done by scanning the container runtime, which will help in detecting potential anomalies and attacks.
- Shift process “to the left”
This is a DevOps principle that allows vulnerabilities in software development to be tested in the early stages. This enables the software delivery processes to have flexible timing.
- Create container security policies
Container security policies should be established for the different container lifecycle phases.
Containers have many benefits, application portability, efficient delivery cycle, faster configurations, and resource utilization to name but a few. However, containerization even when applying the best practices still has its ups and downs. But by judging by its gaining popularity in recent years, it’s definitely the way to go.
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