[sixstringtheory]

Those sound the same to me. Are you drawing a distinction between a repeatable/reproducible process vs result? Like if you run the same command to fetch a dependency, you wind up with different results if the dependency maintainer releases a new update and you aren’t pinning the dependency?

[robbintt]

To use the apt analogy further up in the thread, `sudo apt install git` is repeatable in your dockerfile, but often not reproducible. Later on you will get a different build. Across say 500 packages and 1,000,000 containers (or say 1000 container images if you are deploying images) over even a week this becomes extremely... varied...

[nerdponx]

On smaller scales, this is perfectly fine. How often does Git actually release breaking changes of features that you actually need to use inside your Dockerfile? How often does Debian pull in such a version into their stable OS? And why didn't you just version-pin Git like Hadolint told you to do?

Exact reproducibility is nice for two scenarios: 1) academic research, and 2) very large-scale applications and deployments. For regular people writing boring small web apps, choosing a stable base image and pinning dependencies is good enough.

Consider also that your preferred programming language will also very likely not provide particularly reproducible package builds.

[happymellon]

Although you can.

This just means you don't.

Try using `sudo apt install git=1:2.39.2-1ubuntu1`

That pins it to a particular version so that it should be reproducible.

[j1elo]

Would that work, though?

I've never looked seriously into it, but my feeling is that distros will delete old versions as newer ones are uploaded: When I run "apt-cache policy git" in my Ubuntu, I only see a couple versions available to install, often other packages show only a single one (so, the latest).

[happymellon]

I know that Debian has Snapshot for older packages but you are still at the will of other people and people are fickle, and Nix should allow you to use specific versions to build your base images from to pin to.

However, much in the same way that if you actually take your build system seriously you'll store your application dependencies in a local proxy, you can run a mirror or proxy to hold these historical packages too.

Take a look at something like apt cacher, however it is a proxy cache so you can reproduce builds using the exact same package versions but if upstream delete old packages, and you want to roll back to one you haven't previously downloaded, then you are out of luck.

[nerdponx]

Yes. This can be a problem in scientific research involving numerical code or random number generation, where results can vary even due to small inconsequential-seeming changes, leading to your results not being reproducible scientifically because they're not reproducible computationally.

[thfuran]

Reproducible in that context means that repeating will produce exactly the same output every time.