CODEWITHSUNDEEP
docker
Amiga500
Amiga500

Reputation: 6131

Docker creates two images

I am starting with the docker and its concepts. I have read official Guide on how to create images, and managed to create several images (proud).

Now I actually wanted to build an MySQL server, so I can connect it with my application. For that purpose, I have found official MySQL Dockerfile.

The thing is, when I run it with:

docker build -t mysql .

It creates two images:

  1. First one has debian as Repository and stretch-slim as a TAG. Size is 55MB

  2. Second has none for both. Size is 65MB.

I am now confused. Why two images? My understanding was it will be one image with Debian and MySQL, but not two.

Some guideline are appreciated.

Upvotes: 0

Views: 253

Answers (2)

Facundo Diaz Cobos
Facundo Diaz Cobos

Reputation: 357

If your Dockerfile has a FROM image, it has a dependency on another image, so It will download and generate all the dependant images.

If you need to create a BASE IMAGE you can do it by using a special image called scratch as a parent image.

i.e:

FROM scratch
ADD hello /
CMD ["/hello"]

For more information about how to create a base image: https://docs.docker.com/develop/develop-images/baseimages/#create-a-simple-parent-image-using-scratch

Upvotes: 1

juanlumn
juanlumn

Reputation: 7085

This is the expected behavior:

As you can read in the first line of the docker-library-bot file from MySQL Dockerfile is says:

FROM debian:stretch-slim

As per Docker documentation:

A Dockerfile must start with a FROM instruction. The FROM instruction specifies the Base Image from which you are building.

A base image is an image that has no parent.

So, as a result you will have two images:

  1. debian -> Base Image
  2. mysql -> Image created from the Base Image with mysql and all the software needed to run it.

Upvotes: 2

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