Docker is a service like VMware or KVM VPS service but with different technology.
These days, Docker talk is hot in tech circles and is likely to be heard around the corner from Docker’s definitions. So we’re going to look at what Docker is and why it’s gotten so popular.
A person named Solomon Hykes launched a mechanism called Docker. The goal was to make it easier to interact with Containers. The idea was successful, and in the year 2014 after Docker’s release of version 1.0, we saw its popularity increase.
As a result, companies have launched server-side applications instead of virtual machines in Docker’s platform. It is interesting to note that several large banks were assisted by the technology while Docker was still in version 1.0, which indicates Docker’s high security for the technology in the early version.
Nowadays Docker and Moby, known as the Docker Overhead Collection, have attracted a large audience.
This has led to big names such as Red Hat, Canonical, Oracle, and Microsoft becoming more interested in using Docker, and now almost all of the big ones in the cloud are using Docker.
What Is A Docker Exactly?
Docker provides the ability to run processes and software separately in a completely isolated environment on the Linux kernel, which is called the container and the isolated package.
Container enables application developers to integrate an application with all its modules and related components (such as libraries, functions, etc.) into one package to generate that application in different platforms, and systems run smoothly.
In fact, without having to worry about the settings and dependencies of a particular application on other platforms, you can run that application in any environment.
As mentioned above, Docker manages the containers and acts more like a virtual machine. Docker’s difference with the virtual machine is that in the VM (or virtual machine) to run different applications and programs to work separately, we have to create a separate environment by the name virtual machine.
Different VMs need to be built, which brings with it the burden of processing and wasting system resources on the server.
But in Docker, a Docker module is installed on a particular VM that can be running Windows or Linux, and then Docker services install and run different containers containing different applications without the containers accessing one another. As such, the containers are isolated, eliminating the need for multiple VMs.
Reasons For Docker’s Popularity
If you are familiar with virtualization, you must know that mechanisms such as Hyper-V, VMware, KVM, and Xen make virtualization available to network administrators to create Windows or Linux VPS. As a result, these mechanisms require strong hardware resources.
Containers, on the other hand, use shared operating systems. As a result, we are more efficient at using the resources of the system more efficiently. Unlike hardware virtualization, containers are mounted on top of a Linux Instance, providing a compact space for applications.
Thanks to this feature, something about 2 to 5 times more instances of Xen or KVM VM technology runs on a single hardware. Containers, on the other hand, help developers put their code in a shared repository. This speeds up the coding process and makes the code work better.
Docker enables developers to easily and quickly port their applications to a smaller, portable container. These applications can be run virtually anywhere.
This process is accomplished by separating the code into a single container. It is clear that doing so will make it easier to optimize and update the application. As tech-savvy companies look for more ways to build portable apps, Docker is finding new fans.
In the meantime, if you are familiar with GitHub, you are well aware that this platform has provided the conditions for collaborating on code sharing among developers. In this sense, Docker is a bit like a gateway because the official gateway repository helps businesses to optimize and run their software.
Docker containers, on the other hand, are conveniently located in the cloud computing space, designed to interact with almost all applications using Dev/Ops (Development/Operations) methodology.
Docker provides a local development environment that provides developers with exactly the same server functionality. This is very applicable to the CI / CD development method. This allows you to run multiple development environments from a single host with a single software, operating system, and configuration.
On the other hand, the project can be tested on several new and different servers, and all team members can collaborate on a single project with the same settings. This enables developers to quickly test new versions of their program to ensure it works properly.
Container History And Docker Formation
If you are from the old world of computers, you are likely to remember the FreeBSD Jail that was used late in the year 2000. It is interesting to know that the container history goes back to the same period. Oracle also had its own concept of containers known as Zones.
With that in mind, developers can probably still get help from containers without even knowing it. For example, whenever you use a Google service like Gmail and Google Docs, a new container is actually created for you.
Docker mounts to LXC and, like other containers, has proprietary system files, storage, processors, RAM, and other resources. So the main difference between containers and VMs is that when Hypervisor abstractly creates an entire system, containers only abstract the operating system kernel.
This saves millions of dollars for computing services companies, which is why tech giants are rapidly moving towards Docker.
Standardization Of Containers
Docker provided companies with new tools we had never seen before. Simplification and implementation can be mentioned here. On the other hand, Docker is partnering with other containers from Canonical, Google, and Red Hat, and as a result, we see good standardization for containers.
Docker continues to standardize, and since it is virtually impossible to compete with Docker these days, it can be run on any operating system, resulting in good Docker standardization.
Monitoring And Managing Containers
All IT infrastructures require management and monitoring, and containers must be monitored and controlled. Otherwise, it will not be clear what programs the server is running.
Fortunately, the Dev/Ops (Development/Operations) program can be used to monitor Docker containers, but it should also be noted that these programs are not optimized for containers. This is where you should look for cloud management and monitoring tools.
Tools like Docker Swarm, Kubernetes, and Mesosphere are good options in this regard, and experience has shown that Kubernetes has become more popular among these tools.
Application and use cases of Docker
Docker is used in various cases to improve efficiency and facilitate the work process, and we will mention its main uses.
1. Fast and continuous distribution of programs
Docker simplifies the development process by allowing developers to access your applications and services from locally hosted containers. CI/CD (Continuous Integration/Continuous Delivery Workflow) processes benefit greatly from containers.
Let’s use an example to understand better, developers code locally and need to use Docker to share code between colleagues. Docker is used to deploying applications in a test environment to run manual and automated tests.
Guidance of the application to the test environment helps the developers until after finding and discovering the bugs to fix the defections in the development environment and re-test the programs to verify their reliability. Once validated, delivering the fix to the end user is as easy as publishing a new image to the production environment.
2. Adaptive deployment and scalability
Workload portability is greatly improved with Docker container-based technology. Docker containers can run on any platform, from a developer’s laptop to physical or virtual machines in cloud services, data centers, and hybrid environments.
Docker’s portability and its low resource requirements Impact simplifying the management and dynamic execution of workloads. Also, Docker can change (upgrade or reduce) or remove services and programs in real-time according to business needs.
3. Ability to run large workloads on a single hardware
Docker is introduced as a cost-effective alternative to hypervisor-based virtual machines due to its extraordinary execution speed and the need for fewer system resources.
While Docker provides more computing resources to achieve your business goals, it also saves you money. It is the ideal option for medium-sized deployments and high-density environments that need to run workloads with the occupation of fewer resources.
Docker structure and architecture
The architectural pattern of Docker is client-server-based. Building, running, and distributing your Docker containers are all handled by the Docker daemon, which is communicated with by the Docker client. You can use the Docker client and daemon on your system or use them to connect a Docker client to a Docker daemon running elsewhere.
The Docker client and daemon communication is done by REST API through a network interface or Unix sockets. Docker Compose, as one of the Docker clients, facilitates the management of container programs and enables the use of container programs.
Docker terms and tools
To familiarize you with the tools and terms related to Docker, we will provide explanations:
Each Docker container contains a simple text file describing the steps required to create a Docker container image. DockerFile is a program that can generate Docker images automatically. The image build process is basically a set of Command Line Interface (CLI) instructions that Docker Engine executes. The Docker command set is extensive yet standard; Docker doesn’t care about content, infrastructure, or other external factors and has the same operation.
To run an application in a container, Docker images that containing the executable’s source code, tools, libraries, and dependencies required by the code plays an important role. When a Docker image is run, it creates a new container instance or perhaps multiple instances.
While developers can create Docker images from scratch, they usually get images from shared repositories. Using a base image, Docker makes it possible to create multiple images that share the same stack but with Minor changes included.
Usually, the created images are based on another image that has been customized with additional details; for example, you can use images previously configured by others and available in the registry to create your own images.
Many layers make up Docker images; each layer is associated with a different version of the image. By applying changes to modify an image by the developer, a new top layer is created, which replaces the previous top layer as the latest version of the image. For reusing layers in future new projects, previous layers are saved so they can be accessed and restored when needed.
To develop your own images, you can create a Dockerfile with a simple syntax for describing the processes required to build and run the image. By entering each directive in the Dockerfile, we create a new layer in the image. When making changes and rebuilding images, only the layers that have been modified are recreated.
By creating a container from a Docker image, a new layer is made called the container layer. The container layer holds all the changes applied to the container (deleting and adding files) during the running time and when the container is active. Since many active container instances can be spawned from a single base image while sharing the same stack, they improve overall performance by repeating the image creation process. With the explanations we gave, we could only point out a small part of the efficiency, compactness, and speed of the images compared to other virtualization technologies.
Running instances of Docker images are known as Docker containers. Unlike static, read-only Docker images, dynamic, executable content in containers is constantly updated. Administrators may manage and control them with Docker commands that allow users to interact with them and change their settings and environment.
Docker’s command-line interface (CLI) and API make it easy to create, remove, move, and stop containers. You can attach storage to a container, link they to one or more networks, and even create a new image of the current state of the container.
An isolated container cannot interact with other containers or the host operating system. A container’s network, storage, and other subsystems can be more or less isolated from the networks of other containers and the host machine.
The image and the choices you give it when you build or launch the container make up the container definition. Any state changes that are not persisted in storage are lost when a container is deleted.
Docker Hub is a public repository of Docker images that boasts of being “the world’s largest library and community of container images.” It contains approximately one hundred thousand container images originating from stores such as commercial software companies, open source projects, and individual developers. Images created by Docker, Inc., Docker Trusted Registry, verified images, etc., are all part of Docker Hub.
DockerHub encourages all users to distribute their images freely. Additionally, by downloading and installing these images, they can use the predefined Docker file system base images as a starting point for their containerization projects.
In addition to Docker Hub, GitHub is another well-known type of image repository for storage. Regarding software development and applications that improve teamwork, GitHub shines as a repository hosting service. Docker Hub users have the option to create a repository (repo) publicly or privately to store multiple images, and it can also connect to services such as GitHub and BitBucket.
Docker Desktop is a collection of tools such as Docker Engine, Docker CLI Client, Docker Compose, Kubernetes, etc., for Mac and Windows operating systems and also includes access to Docker Hub.
A service that processes client commands to build, manage, and store Docker images. The Docker Daemon is the hub of your Docker deployment that monitors the performance and execution of your Docker. The server that hosts the Docker daemon for execution is known as the Docker host.
Docker daemon manages Docker objects such as images, containers, networks, and volumes according to Docker API requests and also controls Docker services by communicating with other daemons.
Docker images can be stored and distributed on a scalable open source system called the Docker Registry. Using tags, the registry can identify and track the image versions stored in different repositories in different editions. For this purpose, we use git, a version control system.
By executing the docker pull or docker run command, the required images will be downloaded from the registry that you have customized and configured. The docker push command transferred an image into a registry that you provided.
The Docker client is the primary way that many Docker users communicate with Docker.
By executing a command such as Docker Run, the necessary commands are sent to Docker from the client side for execution. Note that the docker command uses the Docker API, and the Docker client provides the ability to communicate with multiple daemons.
Images, containers, networks, volumes, plugins, and more can all be built and used with Docker. This section serves as a quick introduction to a few of the objects.
Why Docker VPS? What advantages does it provide?
In hosting and setting up a simple WordPress site, users usually do not go to Docker. Still, using Docker to host several different sites is more practical and valuable for developers because running Docker on a VPS gives users more mastery and control over server resources.
Running Dockers on a Linux VPS is more prudent and wiser than running it on a PC because VPS has a more powerful infrastructure with high performance and VPS applications are much easier to manage. Installing Docker on a VPS opens the door to container-based virtualization, which is more secure than conventional virtualization methods, and Docker’s performance will also benefit from hosting on a virtual private server.
Additionally, if you have a Docker VPS, you can share the application image with other servers running the same version of Docker. The things we have mentioned have not fully expressed the advantages of Docker VPS, so we will mention the additional features it offers below:
Organizing and streamlining the host operating system
By separating applications and data using containers, you can make your main VPS operating system more manageable and have more control over the hosting space by reducing the clutter of your operating system. Therefore, your hosting space will be more secure, reliable, and organized.
Each application works independently of the others.
You may encounter failures in the VPS operating system due to coding mistakes, which often involve paying a fee and spending a long time fixing these problems. A crash or defect in the host’s operating system can disrupt the entire performance of the VPS and the programs running on it. But Docker containers provide secure isolation. By isolating the application in Docker containers, you can ensure that the overall performance of your VPS is not affected by any issues.
Ability to host multiple independent applications on a VPS
Hosting two or more websites or applications on top of different software stacks on one VPS is possible with the help of Docker containers. Therefore, the Flexibility of Docker VPS is a significant advantage for developers working on multiple projects because it allows them to work on several projects simultaneously.
The possibility of setting up a complete simulation of the server production environment
Docker containers allow you to set up a staging environment that is similar to a production server, so you can be sure that the server will perform as expected when it comes time to deploy the code.
Security of the operating system through containers
Docker reduces the risk of an application being attacked by hackers by isolating them in separate containers. As a result, containers can increase application security.
Running the same application on multiple VPS
Using Docker images, you can create an exact copy of a website or application hosted on a VPS, then run it from another server as a failover.
A significant advantage is the ability to recover data after unpleasant and catastrophic events that any user may experience when their programs are damaged. In Docker VPS, it is possible to make an immediate backup copy of your program by converting the Docker container to images and using the necessary software.
As noted above, Docker allows more applications to run on other hardware than other technologies with the same hardware, making it easier to build and manage applications.
In the end, we suggest that if you are also interested in new technologies and have already used Docker, share your helpful experiences with us and other users.