Yet another Elixir and Erlang docker image

Nice! How about versions for ARM, so we can easily use it on a Raspberry Pi?

We need to make sure the current images work correctly first but I think we can support ARM in the feature. We don’t have ARM builds of OTP so the first step would be to add cross-compilation to ARM in the Bob OTP builds.

Cool. I am looking forward to it. It’s always a real struggle if you want to use Docker on a Raspberry Pi because many things are just not available for ARM. I think having this sorted out for Elixir will be very helpful.

The “not immutable” image tags have bitten me/us several times. Excited for officially supported community versions. Great work!

Any plans for Debian (stable) slim builds? [buster, at time of this post]

I like Alpine but I’ve actually switched back to buster-slim over subtle concerns around glibc / musl and DNS.

We want to support more OSes and CPU architectures when we know that the images are stable. The first step would be to build OTP against those architectures and OSes. Here you can find our existing linux builds [1], any contributions to support more are welcome.

[1] bob/priv/scripts/otp at main · hexpm/bob · GitHub

This is great news. We’ve been internally pinning the official Docker images ever since the incident with the ssl dep and erlang broke all of our stuff (twice). This will likely save us that trouble in the long run.

Having been stung by the mutable erlang changes (hackney ssl), mutable alpine version (libvips mismatch), and an annoying lag between version release and docker availability; I’m all for this.

I trust the hex team to provide timely and consistent builds more than I trust the unknown (to me) authors of the official image.

Thanks!

Oh it seems that I was not the only one in need of immutable images

╭─exadra37@thinkpap-l460 ~/Developer/Projects/elixir-docker-stack  ‹dev-new-approach› 
╰─➤  sudo docker image ls | grep -i erlang
exadra37/phoenix-dev       1.4.11_elixir-1.9.4_erlang-22.2.1_git   23d45190fd25        3 weeks ago         814MB
exadra37/elixir-dev        1.9.4_erlang-22.2.1_git                 98f3ef6b30ac        3 weeks ago         713MB
exadra37/erlang-dev        22.2.1_git                              96c72e47095b        3 weeks ago         707MB
exadra37/phoenix-dev       1.4.10_elixir-1.9.4_erlang-22.1.6_git   46d86f30f487        3 weeks ago         813MB
exadra37/elixir-dev        1.9.4_erlang-22.1.6_git                 14df71ee5f57        3 weeks ago         712MB
exadra37/erlang-dev        22.1.6_git                              401ebb0c0162        3 weeks ago         706MB

But in my case I have built them as part of an Elixir Docker Stack that automates a lot of stuff for my developer needs, and I compile Erlang, Elixir and Phoenix directly from Github, and I am based on Debian, mainly because of Observer not working in some Alpine based images.

Thanks for this work. I need to try it out, and compare it with my approach, because Alpine based images have not worked for me.

It’s not about Docker, but about how you write the Dockerfile.

If you want a truly immutable docker image until the OS level, then you need to pin everything you install with apt or whatsoever package manager you use to install things in the OS.

But if you want to extend another docker image and have it pinned, you cannot use the tag, instead you need to use the digest hash of it. Read more in the official docs:

Pull an image by digest (immutable identifier)

So far, you’ve pulled images by their name (and “tag”). Using names and tags is a convenient way to work with images. When using tags, you can docker pull an image again to make sure you have the most up-to-date version of that image. For example, docker pull ubuntu:14.04 pulls the latest version of the Ubuntu 14.04 image.

In some cases you don’t want images to be updated to newer versions, but prefer to use a fixed version of an image. Docker enables you to pull an image by its digest . When pulling an image by digest, you specify exactly which version of an image to pull. Doing so, allows you to “pin” an image to that version, and guarantee that the image you’re using is always the same.

Dockerfile Example from docs:

FROM ubuntu@sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2

So no matter how many years we go into the future, the image will be always exactly the same you download since it was built. It’s like a Git commit, if it changes the hash is not the same anymore.