What is the purpose of COPY --from=gloursdocker/docker / /?

[lucassus]

This instruction, for some reason, is used in many examples.
The comment install Docker tools (cli, buildx, compose) in my opinion, is not really helpful.

[zozitak]

google search first result to "gloursdocker/docker" :
https://registry.hub.docker.com/layers/gloursdocker/docker/latest/images/sha256-a66243282b1165f556ec4a91d749c1ebc81dd28bcfbce653ccf49b01ae3b3fdf

[lucassus]

@zozitak thank you. I saw it, but still it's pretty hard to figure out what it exactly does.

[arjuuuuunnnnn]

Copying all the contents of the root directory (/) from the gloursdocker/docker image into the root directory (/) of the current build stage

[ehhc]

Copying all the contents of the root directory (/) from the gloursdocker/docker image into the root directory (/) of the current build stage

Thanks for your answer. I believe, most of us here understand, what that command literally does. I hopped for a bit more explanation on why the root directory was copied and some elaboration about the effects of this copying…

[arjuuuuunnnnn]

Copying all the contents of the root directory (/) from the gloursdocker/docker image into the root directory (/) of the current build stage

Thanks for your answer. I believe, most of us here understand, what that command literally does. I hopped for a bit more explanation on why the root directory was copied and some elaboration about the effects of this copying…

When you build a Docker image, each instruction in the Dockerfile creates a new layer on top of the previous one

gloursdocker/docker this is the official docker image which has all the base files required for the application

so here we are copying the entire contents of the gloursdocker/docker to our docker image
as there is already an image of gloursdocker/docker which is official image of docker

we need not build the same image again and used the cached one from gloursdocker/docker
also coming to the question 'why the root directory was copied'

• to include the entire contents of that base image as the foundation for the new Docker image being built