AArch64 for 18.03

[dezgeg]

Let's get AArch64 support into a reasonable state for 18.03.

• nixos/release.nix: Refactoring for better multi-system support #33749 Make Hydra build the aarch64 sd-image (For Raspberry Pi 3 as the main hardware target) similar to how the ISOs are built: https://github.com/NixOS/nixpkgs/blob/master/nixos/release.nix#L144
• Refactor x86-isms in https://github.com/NixOS/nixpkgs/blob/master/nixos/release.nix
• Implement the Packet image: [tracking] aarch64 build on Packet Type 2A #31606. I have some progress in make-disk-image: Support creating EFI images #32618.
• ZHF: 18.03 Zero Hydra Failures - aarch64 edition #32326. Let's target to having less failures than Darwin ;)
• Perhaps migrate some documentation from the Wiki to the official docs.

[dezgeg]

#33749 is the first part of the 'refactor x86-isms from release.nix`

[Ericson2314]

@dezgeg I was already planning on doing some https://github.com/NixOS/nixpkgs/blob/master/nixos/release.nix and https://github.com/NixOS/nixpkgs/blob/master/nixos/release-lib.nix overhaul for cross, lets coordinate.

[dezgeg]

@Ericson2314 sure, do you have some code written already somewhere? https://github.com/NixOS/nixpkgs/pull/33951/files is the next one up which is very similar to the previous PR and I don't expect any future ones to differ much either.

[bachp]

What's the best way to help testing NixOS on a Raspberry Pi? Is there a place to get an image?

[dezgeg]

See https://nixos.wiki/wiki/NixOS_on_ARM & related wiki pages.

[vcunat]

Now I wonder about the approach to 18.03 – two options:

1. share with x86_64-linux, i.e. common pair of jobsets and channels for both; or
2. split like we do with x86_64-darwin, i.e. separate jobsets and separate channels.

[vcunat]

I think for the stable stuff it might be easier to have (1), assuming that we really want Zero Hydra Failures for aarch64 (i.e. explicitly disable on aarch64 whatever we don't fix).

[vcunat]

Well, I had to go for (2.) for now, as Hydra currently can't manage the evaluation in a nixos jobset with two platforms. (too many heap sections etc. I tried more than five times without any success.)

[grahamc]

IMO we have to fix Hydra to allow this to build, because managing a deployment of aarch64 and linux with nixops becomes frustrating at best and impossible at worst if they don't share a common channel.

[vcunat]

I think we can manage to fix it until release.

[grahamc]

I wonder if bumping the initial heaps again on Hydra would do the business: https://github.com/NixOS/nixos-org-configurations/blob/master/delft/hydra.nix#L75

[vcunat]

Yeah, that sounds like a promising work-around. Even if it would mean to reduce the number of parallel evaluations a little. It might actually save some work, due to the waste. (Even trunk-combined gets a nontrivial fraction killed due to this.)

[7c6f434c]

Isn't it enough to have two channels with the same revisions? Is it possible to have a repository which tracks beginning of a Hydra build (as opposed to already existing channel-bump branches), and have a job that builds aarch64 based on that?

[7c6f434c]

(I am not arguing against fixing Hydra builds of multiple platforms, I am just trying to put a bound on the worst-case loss)

[peterhoeg]

Should this be moved to 18.09 or can it be closed?

[samueldr]

Closing, nothing exactly relevant still to do, except maybe the documentation one. See #65350 for that one.