bergkvist/includeimage repository overview

See https://github.com/moby/moby/issues/3378⁠

⁠bergkvist/includeimage

Dockerfile syntax extension for combining multiple Docker images into one.

⁠Usage

⁠Syntax

INCLUDE <image>:<tag>

⁠Example

#syntax=bergkvist/includeimage
FROM alpine:3.12.0
INCLUDE rust:1.44-alpine3.12
INCLUDE python:3.8.3-alpine3.12

⁠How to build

Remember to use Docker buildkit when building, as seen below.

DOCKER_BUILDKIT=1 docker build -t myimage:latest .

⁠Behavior

• The entire file system of an included image is copied over
• The environment variables of the included image is merged in
  • PATH gets special treatment
• CMD and ENTRYPOINT of included image is ignored.

How it is implemented:

# All the file system contents are copied over (using multi-stage builds)
COPY --from=<image>:<tag> / /
# We extract the environment variables from the included image
ENV <-(merge)- docker inspect <image>:<tag> --format='{{.Config.Env}}'

⁠Current Issues/Limitations

• Currently only supports including amd64 linux images.
• The PATH variable will eventually contain a lot of duplicate entries. This could probably be cleaned up, but shouldn't cause any issues. (I think)