Lightweight OCaml Docker Images created by dune with Multi-Stage Builds

Asya-kawai · June 2, 2021, 11:16pm

I’ve written an article of Docker multi-stage Build for lightweight OCaml application using dune.
I refered this article(Lightweight OCaml Docker Images with Multi-Stage Builds) and customized to use dune.

github.com

Asya-kawai/blog/blob/main/20210603/how-to-create-minimum-ocaml-docker-image-en.md

# How to make the smallest OCaml Docker container image

OCaml used to use a build tool called `jbuilder`.

However, since 2018, it has been replaced by a project called `dune`.
This page shows how to build an application with `dune` and create a minimal Docker container image.

See: [dune migration](https://dune.readthedocs.io/en/latest/migration.html?highlight=Jbuilder#migration)

## Install opam

`opam` is a package management tool for OCaml.

You should install it beforehand, because you use it to install OCaml libraries (modules) and tools such as `dune`.

Execute the following command to install `opam`.

Note that the environment to install is `Ubuntu 20.04`.

```

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Please feedbacks!

yawaramin · June 2, 2021, 11:24pm

Nice write-up! You can also use opam lockfiles for reproducible builds: Lock file and dev dependencies with opam

The main difference in the Dockerfile will be:

opam install . --deps-only --locked

You won’t need to specify the packages in the install command, since they will be in the lockfile.

Asya-kawai · June 3, 2021, 12:47am

Thank you for your feedback!

I didn’t know opam-lock,
It’s sounds good!

I’ll learn about this tool and update the Dockerfile and articles.

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