Why do you need a basic image with Docker?

Question

I looked at every page of the Docker documentation.

I don’t understand yet why to install containers before installing / creating the application environment you need a “base image” (for example, a Ubuntu base image).

My questions:

• What is a base image and why is it required?
• Why is it impossible to create a container and put in it an application similar to virtualenv from Python?

Answer 1

In fact, Docker works through the application of layers that are added to the base image. Since you need to maintain consistency between all of these levels, you cannot create your first image on a moving target (i.e., in your recordable file system). Thus, you need a read-only image that stays the same forever.

Here is an excerpt from the Docker image documentation:

Because Docker uses the Union file system, processes assume that the entire file system is mounted read-write. But all the changes go to the topmost layer that is writable, and underneath the source file in read-only mode remains unchanged. Since the images do not change, the images have no state.

Answer 2

In simple words, I can explain that ... we use certain libraries and node packages for our application in a similar way, we can use Core images that are already made, and use them with a simple search. You can also define your own base image and use it.