Docker instead of an Elixir version manager (split thread)

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Yes you can and you should… that is all the point of using Docker, to have reproducible builds.

You need to use the Docker Image Digest of an image instead of using the Docker Image Tag.

Dockerfile:

FROM ubuntu@sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2

CMD bash

╭─exadra37@laptop ~/test
╰─➤  sudo docker build -t test .
[sudo] password for exadra37:
Sending build context to Docker daemon  2.048kB
Step 1/2 : FROM ubuntu@sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2
sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2: Pulling from library/ubuntu
5a132a7e7af1: Pull complete
fd2731e4c50c: Pull complete
28a2f68d1120: Pull complete
a3ed95caeb02: Pull complete
Digest: sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2
Status: Downloaded newer image for ubuntu@sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2
 ---> 07c86167cdc4
Step 2/2 : CMD bash
 ---> Running in f49d4193090b
 ---> 7422164e3384
Removing intermediate container f49d4193090b
Successfully built 7422164e3384
Successfully tagged test:latest
╭─exadra37@laptop ~/test
╰─➤  sudo docker run --rm -it test
root@22f3f656e58e:/# lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 14.04.4 LTS
Release:	14.04
Codename:	trusty
root@22f3f656e58e:/#

As you can see this build is immutable and reproducible in many years ahead in the future :slight_smile:

More reading:

https://medium.com/@tariq.m.islam/container-deployments-a-lesson-in-deterministic-ops-a4a467b14a03

For security reasons I don’t trust in third part images, just the official ones, thus I always build my ones from officials ones, thus never had issues like the one you described.

Plus building images in top of a chain of other images is asking for trouble, is like using inheritance in OOP languages, that I avoid at all costs.

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