Add documentation for Flakes

[sevanspowell]

• Add some beginning resources for understanding Nix Flakes.

[rvl]

Excellent, thanks @sevanspowell !

Can we put all the files flat under docs/code/nix and use order to control their ordering?

And there are also some (but not all) sections from cardano-wallet/docs/contributing/Nix.md that could be integrated here.

[rvl]

Can we cut down the examples so that they are still self-contained, but only deal with the topic of this page?
For example, remove pinning of nixpkgs, unless the page is about version pinning.

But here is a more interesting example of what could be put in the shell:

Suggested change

	{
	description = "A very basic flake";
	inputs = {
	nixpkgs.url = "github:NixOS/nixpkgs/nixos-21.11";
	};
	outputs = { self, nixpkgs }:
	let
	pkgs = nixpkgs.legacyPackages.x86_64-linux
	in {
	devShell.x86_64-linux = pkgs.mkShell {
	nativeBuildInputs = [
	pkgs.python3
	];
	};
	};
	}
	```
	{
	description = "Flake with a development environment";
	outputs = { self, nixpkgs }: {
	devShell.x86_64-linux =
	with nixpkgs.legacyPackages.x86_64-linux;
	mkShell {
	nativeBuildInputs = [
	(python3.withPackages (ps: [ ps.numpy ps.toolz ps.requests ]))
	];
	};
	};
	}
	```
	This is an example of adding Python and some Python Wheels to the shell. More information (for those interested) can be found in the
	[Nixpkgs Manual Python section](https://nixos.org/manual/nixpkgs/stable/#python).

[sevanspowell]

This builds on tutorial 2, and so I left the version pinning in to minimize required code changes from the last flake.nix, but feel free to remove.

[rvl]

Could we also integrate some of the material from these documents?

• https://github.com/input-output-hk/iohk-nix/blob/8b1d65ba294708b12d7b15103ac35431d9b60819/docs/nix.md
• https://github.com/input-output-hk/cardano-node/blob/468f52e5a6a2f18a2a89218a849d702481819f0b/doc/getting-started/building-the-node-using-nix.md#building-under-nix

[rvl]

NixOS-specific instructions probably aren't necessary. Especially because nix.extraOptions has become nix.settings.experimental-features in the latest nixos-unstable versions.

[rvl]

Simplest way is probably to ask users to run:

nix upgrade-nix

If that doesn't work, then reinstall it using the instructions here: https://nixos.org/manual/nix/stable/installation/installing-binary.html#multi-user-installation

[Unisay]

Doesn't work on NixOS

  nix upgrade-nix 
error: Nix on NixOS must be upgraded via 'nixos-rebuild'

[rvl]

I have a feeling this will go out of date, and the original sources could just be linked.
On the other hand, the flake schema is not well documented.
The resources I use are:

1. Schema - https://nixos.wiki/wiki/Flakes#Flake_schema
2. Input references - https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-flake.html#flake-references
3. Installables - https://nixos.org/manual/nix/stable/command-ref/new-cli/nix.html#installables

[Unisay]

One other benefit of this new format is that it facilitates composability, so it becomes easier to connect one flake's outputs to other flake's inputs.

[JBlaze2029]

I do not want this service and did Not apply for it

…

On Fri, 22 Apr 2022, 7:42 am Yura Lazarev, ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In docs/code/Flakes/Tutorials/Installation.md <#23 (comment)> : > @@ -0,0 +1,40 @@ +--- +title: 01-Installation +date: 2021-02-09 +--- + +Presuming nix is already installed, Nix flakes are available from Nix version 2.4 and up. + +## Non-NixOS + +``` +$ nix-env -iA nixpkgs.nixUnstable # or nixpkgs.nix_2_4 Doesn't work on NixOS  nix upgrade-nix error: Nix on NixOS must be upgraded via 'nixos-rebuild' — Reply to this email directly, view it on GitHub <#23 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AP6TJ4ZMJKWHYBGQWQ72NDTVGKGEBANCNFSM5N7O6TLQ> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>