Utilising the Nix 2.12 features regarding builds

[573]

It would be nice to be able to adopt the new https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-auto-allocate-uids and https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-use-cgroups in my ci build.

Is there a possibility to explain the background of the settings a bit and maybe come up with a minimal, i. e. but not neccessarily github-action, workflow file.

[infinisil]

I'm thinking this would not be entirely suitable for a Nix hour. It seems like the docs are decently clear on what they do.

maybe come up with a minimal, i. e. but not neccessarily github-action, workflow file.

I don't think there's anything specific regarding CI with those features.

Why auto-allocate-uids? Traditionally you had to allocate separate build users for the Nix daemon, such that each parallel derivation build could use a separate user without the possibility of being able to access each others files. This then leads to the problem that if you have less allocated build users than cores on a system, you can't use all of them. By automatically allocating build users, they dynamically scale as necessary.

Why use-cgroups? That's explained in the PR that implements these two features: NixOS/nix#3600.

I hope that helps, let me know!

[infinisil]

We might look into this a bit after all, because this week the topic is going to be various experimental features: #65!