Docker – Containers & Hosts

A common containerization tool in DevOps is Docker. It is an application deployment platform as a service for Docker containers. It consumes the least amount of resources, can be deployed more rapidly, and can scale easily while running your application inside of a container. 

1. Containers – Containers are “packages” of software that include an application’s source code, libraries, configurations, and dependencies. They make it easier for software to execute consistently and reliably across several machines.
2. Docker Host –  A real or virtual server that houses the Docker engine, Docker’s main component, is referred to as a “Docker host.” Workloads are contained and executed in Docker containers using the Docker engine.

Uses of Docker 

• An open-source programme called Docker is used to create, test, deploy, and execute web applications in a particular virtual setting.
• Docker assists in lowering the amount of hardware resources required to keep running programmes stable and effective. 
• It is also one of the best solutions for developers who want to swiftly upscale or relocate pre-made software products to new environments without worrying about the project’s dependability or any other concerns.

Docker Network Host

The host in Docker is the computer that is in charge of managing one or more containers. A networking configuration known as Docker network host, also referred to as Docker host networking, allows a Docker container to share its network namespace with the host computer.

Docker Container

A byproduct of containerization is the container. It is fundamentally pretty similar to a virtual machine, but much smaller and focused on sustaining just one programme as opposed to a fully-fledged OS with numerous software tools. An alternate method for creating virtual computers is containerization. Developers construct software clones of computers where their applications are launched and executed rather than employing hardware virtualization.

Hosting of Docker Containers 

The hosts that DevOps experts or developers deal with are similar to any other hosts, including those that support Docker containers. But it’s crucial to pick the host that will provide you with a dependable, complete platform for your project from among the available hosts.

Docker Hosts 

A Docker host is a piece of hardware that supports Docker containers and the operating system; in essence, this is the server. A machine that is located someplace in the hosting company’s data centre and operates round-the-clock to maintain your website or web application.

The Docker engine isolates its containers from one another and shares a portion of the host’s computational resources with them, much like a hypervisor. It does not execute unique guest operating systems for each of its containers, in contrast to a hypervisor. The Docker host kernel is shared by all containers. As a result, workloads in containers are unable to leverage capabilities that the Docker host kernel does not support. 

How are Docker Containers Connected to the Host?

We execute the command docker run at the very beginning when we construct a Docker image and are prepared to launch the container for the first time. However, it won’t function as intended because a developer must forward ports in order for containers to access hosts and vice versa. Sometimes a large number of project files are saved on a local system while being intended to be maintained and accessible within containers, necessitating the connection of Docker containers to the host. Therefore, while launching virtual machines, the developer must utilise additional settings in order to reach the host from the Docker container.

To access the Docker container from your host the following steps need to be performed:

1. Open your Docker project’s saved directory first.
2. Then use the command docker container ls to view every container that is currently running on your server.
3. Then run the command docker exec -it /bin/bash [name of the Docker container].

The Docker container from your host is accessed now. You can manipulate your container however you like after connecting to the docker container from the host as stated.

Docker-Host IP

The IP address that users of containerized apps use is the first one. The second is the IP address of the Docker container itself, which is utilised by various containers on a single host to interact, remain connected, and efficiently manage shared data (databases, logs, etc.).To make interactions between different Docker containers manageable, you must be aware of their IP addresses.

There are three ways to get a Docker container’s IP address: 

1. The easiest way is to use the command docker inspect. Using the command line you must write something like docker inspect [name of your docker container]. 
2. Another method is docker exec. Using the command line you must write docker exec [name of the container] cat /etc/hosts. 
3. The third is the use docker exec but inside the Docker container. Using the command line you must write docker exec -it [name of the container]. After that, you can access the container’s data.

Difference between a Docker Host and a Docker Container 

DOCKER HOST	DOCKER CONTAINER
Docker Engine is the base Engine that handles the containers.	Docker Container allows developers to package applications with all necessary  components, including libraries and other dependencies.
It can be termed as the server machine on which Docker runs.	It can be termed as  a runtime instance of an image.
Docker host can be Bare metal, VM image, iso, image hosted on some clouds etc.	Docker Containers contain binaries, libraries, and configuration files along with the application itself.

Conclusion

So Docker is basically used as an as an application deployment service for Docker containers. It is a smart decision to host the containers where Docker host is a piece of hardware that supports Docker containers and the operating system and Containers are packages of software that include an application’s source code that make it easier for software to execute consistently and reliably across several machines.