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This article mainly explains "what is the image of docker container". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what is the image of docker container".

The so-called mirror image is a static concept. A mirror image consists of several read-only layer layers. A basic container image is actually a rootfs that contains the operating system's file system (files and directories) but does not contain the operating system's kernel.

Rootfs is a brand new file system mounted on the root directory of the container. This file system is independent of the host file system and is a completely independent file system used to provide the environment for the container.

For a docker container, you need to switch the system root directory in the container to rootfs based on the pivot_root instruction. With this rootfs, the container can build a complete file system for the process and achieve environment isolation from the host. It is with rootfs that container-based local applications are consistent with cloud applications.

In order to facilitate the reuse of images, Docker introduces the concept of Layer in mirrors, which can stack different images layer by layer. In this way, if we want to make a new mirror, we can continue to do it based on a mirror that we have already done.

For example, in a layered solution, the bottom layer is the operating system boot, the top layer is the basic image layer (Linux's file system), and then there are various application images we need. Docker will mount these images on a mount point, and these image layers are read-only. Only the top container layer is readable and writable. It can mount all different directories in the same directory.

The principle is applied to the Docker image. For example, Xiao Wang has made an image of the Java environment based on Linux, and Xiao Li wants to build a Java Web environment, so he no longer has to do the image of the Java environment. He can directly add Tomcat to the image based on Wang's image and generate a new image.

Thank you for your reading. the above is the content of "what is the docker container image". After the study of this article, I believe you have a deeper understanding of what the docker container image is, and the specific usage needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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