Docker Architecture and Components (Registry, Containers, Host, Client, Daemon)
Docker Architecture and Components Explained (Registry, Containers, Host, Client, Daemon). Docker is an excellent tool for DevOps. It’s a powerful software that has an interesting architecture. To extract the desired results using the tool, you need to understand the elements linked to the software.
We have structured the breakdown of its architecture to enable you to dive deep into the topic. But before we learn about Docker’s architecture, you need to understand the basics.
So let’s get started with Docker advantages and the move onto Docker Architecture and Components.
Advantages of Docker Over Virtual Machine
A virtual machine is a server that emulates a hardware server. A virtual machine is dependent on the physical hardware to create the same environment for installing your applications.
You can use a system VM that runs on the operating system as a process and allows you to substitute a real word environment. You can process virtual machines that enable you to execute computer applications in the virtual environment.
Modern age virtual machines have helped users bypass the situation where each VM had an individual operating system that made the processing heavy and took a lot of space.
Now with Docker containers, you have a single operating system, and the resources are linked between the containers. It’s lightweight and boots within seconds.
Advantages of Docker
- Resource Efficiency – Using Docker, the container’s host kernel and the process level isolation become more efficient than the virtualization of the system server.
- Portability – The dependencies for different applications are piled up in the container. They can be easily displaced from tests, development and different production environments.
- Continuous Testing and Testing – Docker has consistent environments and versatility with patching. This feature has made Docker a quality choice for different teams that move towards DevOps approach for different software delivery.
- Allows easy tracking – Docker enables the users to easily track the container versions and quickly examine the difference between the previous container versions. It can enable the user to ensure that there’s no misunderstanding and the results are achieved effectively.
- Cost effective – Docker reduces the infrastructure and maintenance cost to save the expenses and channel your funds towards improving the core business operations.
Know More About Docker
It is an open source project offering a robust software development solution called containers. You need to know more about containers if you want to understand the working of Docker.
Docker packages, provisions, and runs containers. Each container shares the services with the underlying operating system. Docker can also run within a virtual machine if you want to use its benefits within the virtual environment. Docker aims to let the users run microservices applications in a distributed or spread architecture.
Docker can run different containers on the same OS using the kernel’s resource isolation. It offers an easier and quicker configuration to the user and enables you to create an isolated environment to manage the applications.
If we compare Docker with virtual machines, the software moves up the abstraction of resources between the operating system and hardware levels. It enables the realization of multiple benefits of containers like infrastructure separation, application portability and self contained microservices.
While VMs abstract the hardware server, containers are focused on the operating system kernel if we boil it down.
The new approach of Docker brings a change in the approach to virtualization and makes the instances more lightweight and faster. Docker was created to work with Linux, but now it offers greater support for different non Linux OS, including Apple OS X and Microsoft Windows.
Docker Architecture and Components
The Docker architecture is based on the client server model and consists of Docker Host, Docker Registry/Hub, Docker Clients, Storage and Network components.
Let’s dive into the details.
Docker Registry, Containers, Host, Client, Daemon
Docker Host
The host provides a robust environment to run and execute the applications. It comprises images, containers, storage, networks and Docker daemon. The daemon is responsible for the container related acts and receives commands via the REST API or the CLI.
It can communicate with other daemons to organize and manage the services.
Docker’s Client
Docker users can use clients to interact with Docker. The client sends the commands to the Docker daemon when the docker commands run, which executes the commands.
The Docker API is used by the commands that enable the Docker client to communicate with one or more Daemon. The Docker client reports to the Docker daemon, that performs packaging, distributing and executing steps in the Docker containers.
Docker Registry
The Docker registries are the services that provide locations from where the image storage and downloading happens. A Docker registry contains different Docker repositories that host more than one Docker image.
The public registries include two different components known as Docker Hub and Docker Cloud. You can use the private registries for communicating within the organization environment.
The common commands used while working with registries are docker pull, docker run, and docker push.
Docker Objects
1. Containers
They are sort of encapsulated ecosystems that enable you to run the applications. Containers are defined by the image and other additional configurations provided on starting the containers.
The containers have access to the resources defined within the images unless and until additional access is defined while building the image in a container.
You can create a new container image based on the current state. Since the containers are smaller than virtual machines, they can be spun within seconds.
You get a better server density when the spin happens.
2. Images
Images are read only binary templates that can assist in building containers. They have the metadata that describes the container’s needs and capabilities.
Images are used to ship and store applications. You can use images to build a container or add customization with different elements for extending the present configuration.
Docker images have the dependencies required to execute the code within the container.
You can share the images across teams within your organization with the assistance of a private container registry. You can also share the container images with the world using a public registry like the Docker Hub. Images are a vital element of the Docker experience as you can use them to enable collaboration between developers in different ways that weren’t possible before.
3. Networks
Docker networking is a fine passage through which the isolated containers communicate. It is responssible for establish communication between Docker containers and the outside world via the host machine where the Docker daemon is running. There are five network drivers in the docker:
- Bridge
- Host
- Overlay
- None
- Macvlan
4. Docker Storage
You can store data in the writable layers of the containers, but you also need a storage driver to complete the process. Being non persistent, Docker perishes what’s not running in the container.
It is not easy to perform data transfer, but you have four options offered by Docker concerning persistent storage.
- Data volumes – Data volumes enable you to create persistent storage, list volumes, rename volumes, and list the containers associated with the volumes. Data volumes are placed on different host file systems outside the container’s copy and are highly efficient.
- Storage plugins – Storage plugins enable you to connect with external storage platforms. The plugins map storage from the host to external sources like an appliance or a storage array.
- Directory mounts – You have another option to mount the host’s local directory into the container. The volumes need to be within the Docker volumes folder, and any directory on the host machine can be utilized as the volume source when the volume comes to Directory Mounts.
What is Docker’s Workflow?
To understand how the Docker system works, we need to look at the Docker Engine and its multiple components. The Docker Engine enables you to assemble, develop, run, and ship applications using the below listed components:
Docker Engine REST API
The Docker Engine REST API is used by applications to communicate and interact with the Docker Daemon. The Docker Engine API is a RESTful API accessed by an HTTP client such as wget or curl, or the HTTP library which is part of most modern programming languages. If Go or Python don’t work for you, you can use the Docker Engine API directly.
Docker Daemon
It is a persistent background process that handles Docker images, containers, storage, volumes and networks. The Docker Daemon manages the Docker API requests and quickly processes them to deliver the desired results.
Docker CLI
The client Docker command line interface interacts with the Docker Daemon and significantly simplifies how to manage container instances.
Docker CLI is a key reason why multiple developers love using Docker. The Docker client interacts with the Docker Daemon that performs the heavy lifting of the running, building, and distributing of the Docker containers.
Both the Daemon and client can run on a similar system. You can also connect a Docker client to a remote Docker Daemon, where you can handle the operations.
The Docker Daemon and client communicate over a network interface or UNIX sockets using a REST API. The workflow is not complex, and you can use the software to maximum potential for achieving desired results.
Now that you know the different components of Docker Engine look at the implementation of Docker.
Implementation
Docker can be implemented across different platforms like:
- Server – Windows Server 2016 and Various Linux distributions
- Desktop – Windows 10, Mac OS
- Cloud – Microsoft Azure, IBM Cloud, Amazon Web Services, and Google Compute Platform.
Docker Architecture and Components Explained (Registry, Containers, Host, Client, Daemon)
Docker Architecture and Components Explained Conclusion
Now that you know the Docker architecture, you can use the software with finesse to explore its wide range of features to extract the desired benefits.
You can ensure that you understand different architecture or workflow issues when something goes wrong. Docker is a great tool for building containers, and you can utilize it to its maximum potential.
