Is it possible to merge two base images in Docker?

[Nefcanto]

Description

I did not know where to post this feature request related to the Dockerfile. Thus, I sent it here.

I'm stuck at this problem. I have a custom image for my API that inherits from FROM mcr.microsoft.com/vscode/devcontainers/dotnet:8.0-bookworm-slim, and I have other custom images for my website and react panel that inherits from FROM node:lts-bookworm-slim.

However, I need node.js in my API projects, and I also need some stuff that I install in my custom API image, in my react and site images.

I need to be able to create a common base image that combines both mcr.microsoft.com/vscode/devcontainers/dotnet:8.0-bookworm-slim and node:lts-bookworm-slim into one final image. Then I can install my common npm packages and apt packages on that merged image, and use it for all of my needs for API, React panels, Qwik sites, ...

Can you please add that functionality? Is that possible? Is it an easy task?

[thompson-shaun]

Hello! There might be some confusion here concerning Docker layers and execution. In such a case, I suggest selecting a single base image and then adding any missing functionality to that base.

As a path forward, it might be best to become familiar with multi-stage builds and then leverage the dockerfile best practices to craft a Dockerfile that can achieve the end product you're looking for.

Alternatively, based on the tech stack mentioned, it might be helpful to evaluate using docker compose to run multiple containers as a single stack. You can even use compose with devcontainers.

[tonistiigi]

To merge layers from both images together you can do

FROM mcr.microsoft.com/vscode/devcontainers/dotnet:8.0-bookworm-slim
COPY --link --from=node:lts-bookworm-slim / /

If that resulting image works is another question. Probably not as node:lts-bookworm-slim is already a full image, not just the node package that you probably want on top of you base image instead.