What is Docker core?

What is the core of Docker?

1. The image itself is read-only;

Simply put, a container is a running instance of the image. The difference is that images are just static read-only files, while containers have a writable file layer needed at runtime.
If you think that a virtual machine is a simulated set of operating systems (including the kernel, application runtime environment and other system environments) and applications running on it,
then the docker container is an independently running one (or a group of ) application, and its necessary operating environment.

2. The docker warehouse is similar to the code warehouse. It is a place where docker centrally stores image files;

It should be noted that the repository (repository) should not be confused with the docker warehouse and the warehouse registration server (registry). ) confusion.
The warehouse registration server is where warehouses are stored, and multiple warehouses are often stored on it.
Each warehouse stores a certain type of images, often including multiple image files, distinguished by different tags.
For example, there are multiple warehouses in the warehouse registration server below, including Ubantu warehouses, CentOS warehouses, and many other warehouses.

3. The Docker image is similar to a virtual machine image and can be understood as a read-only template.

Docker container is similar to a lightweight sandbox. Docker uses containers to run and isolate applications.
A container is an application running instance created from an image. It can be started, started, stopped, and deleted, and these containers are isolated from each other and invisible to each other.

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