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Today, I will talk to you about what docker clusters and mirrors are. Many people may not know much about it. In order to make you understand better, the editor has summarized the following for you. I hope you can get something from this article.

What are docker clusters and mirrors?

Clustering and mirroring are two concepts that we often see in docker containers, so let's parse what they mean respectively.

1. A cluster is a group of machines that run docker and join in a group.

After joining the cluster, you can continue to run your own docker commands, but now these machines are executed on the cluster by the cluster manager. The machines in the cluster can be physical or virtual, and after joining the group, each machine is called a node.

The cluster manager can use different policies to manage the running containers, for example: the emptiest node command is used to populate the least utilized containers; global ensures that each machine can only get one instance of the specified container. You can write these policies to a file to execute the policies of the cluster manager.

The cluster manager is the only machine in the cluster that can execute commands, and you can also authorize other machines to join the cluster management work.

2. The image is the cornerstone of the Docker container, and the container is the running instance of the image. Only with the image can the container be started.

The image provides a basic operating system environment in which users can install and configure software as needed. Each image has a text file, Dockerfile, that defines how to build the Docker image. The new image is generated from the base image layer by layer, and each installation of software is tantamount to adding one layer to the existing image. The advantage of a hierarchical structure for Docker images is the sharing of resources.

When the container starts, a new writable layer is loaded to the top of the mirror, which is called the container layer, and below the container layer is called the mirror layer. Only the container layer is writable, and all mirror layers below the container layer are read-only. Any changes to the container will only occur in the container layer.

Here, all the mirror layers work together to form a unified file system, and what the user sees in the container layer is a superimposed file system.

After reading the above, do you have any further understanding of what docker clusters and mirrors are? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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