Mirror definition : A mirror represents a software package used to package the software operating environment and software developed based on the operating environment. It contains everything needed to run a certain software, including code. Libraries, environment variables and configuration files needed for runtime.
Why is the image so big:
A software image is not only the original software package, but also includes the operating system required by the software, the software's own dependencies, and its own software package composition.
Why docker mirror adopts the principle of layered mirroring
Note: When docker designs a mirror, each mirror is composed of n mirrors together ----- "The mirror is like a flower roll composed of layer by layer.
UnionFS: Union File System: It is worth multiple file systems at a time, but from the outside, only one file system can be seen. Joint loading will superimpose all layers of file systems, so that the final file system will contain all underlying files And directory.
The biggest feature of the UnionFS layering mechanism is decoupling. The biggest advantage is resource sharing. The layering mechanism is used to realize the basic layer sharing, thereby reducing the overall volume of the docker warehouse.