Unclear Step 1 documentation for installer

[HtwoO]

I am rather new to Nix and evaluating nix as a replacement for Homebrew. I have nix installed on my macOS and wanted to try nix-darwin.

I first followed https://davi.sh/til/nix/nix-macos-setup/ for setting up nix-darwin. It refers to ./configuration.nix in ~/.config/nix/flake.nix, but I have no idea what is supposed to be in configuration.nix

Then I found https://daiderd.com/nix-darwin/ and the steps described there to install nix-darwin is the same as the README.md here. At https://github.com/LnL7/nix-darwin/blob/master/README.md?plain=1#L82 it is unclear what is the relationship between configuration.nix and flake.nix in Step 1.

And in the file ./result/bin/darwin-installer downloaded by https://github.com/LnL7/nix-darwin/blob/master/README.md?plain=1#L19 I could see it will installed something in $HOME/.nixpkgs

List of config files I have edited on my system:

• /etc/nix/nix.conf
• ~/.config/nix/nix.conf

My current system environment:

macOS.CLI> uname -a
Darwin hostname.local 20.6.0 Darwin Kernel Version 20.6.0: Thu Jun  8 22:36:09 PDT 2023; root:xnu-7195.141.49.701.4~1/RELEASE_X86_64 x86_64

macOS.CLI> nix-info --host-os
system: "x86_64-darwin", host os: Darwin 20.6.0, macOS 10.16, multi-user?: yes, version: nix-env (Nix) 2.23.0, channels(root): "nixpkgs", nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixpkgs

macOS.CLI> nix --version
nix (Nix) 2.23.0

I believe nix-info reported wrong macOS version, it should be macOS 11.7.8 (20G1351).

PS: I like the approach of using XDG_BASE_DIR standard for nix, as I have other Linux hosts that I may want to transition to NixOS in the future.

-- Fonzie

[HtwoO]

BTW, I was able to follow https://nixcademy.com/2024/01/15/nix-on-macos/ and run

nix run nix-darwin -- switch --flake path.to.initial.flake

without obvious error, but could not find nix-darwin or darwin-rebuild after the command. I then run nix-store --gc and run the command again and found out it was much slower, not sure why. Maybe because the first time it downloaded stuff from https://mirror.sjtu.edu.cn/nix-channels/store configured in /etc/nix/nix.conf and the second time I saw it downloaded from https://cache.nixos.org.

The following is the content of my current /etc/nix/nix.conf:

experimental-features = nix-command flakes
# trusted-substituters = https://mirror.iscas.ac.cn/nix-channels/store https://cache.nixos.org/
substituters = https://mirror.sjtu.edu.cn/nix-channels/store https://cache.nixos.org
build-users-group = nixbld
trusted-users = my.current.username

I can see it's now a symlink to a file in /nix/store/

macOS.CLI> ls -l /etc/nix/nix.conf
lrwxr-xr-x  1 root  wheel    24B  6 29 17:46 /etc/nix/nix.conf -> /etc/static/nix/nix.conf
macOS.CLI> ls -l /etc/static/nix/nix.conf
lrwxr-xr-x  1 root  wheel    52B  1  1  1970 /etc/static/nix/nix.conf -> /nix/store/kbxh2adn9rpc03ls888z5485v3fq7rkb-nix.conf

Previously, I would occasionally hand edit /etc/nix/nix.conf, but now that it's a symbolic link to a file in /nix/store/ I should not hand edit the file any more. Am I right?

How do I reverse the effects/changes applied by nix run nix-darwin -- switch --flake ...?

[rennsax]

without obvious error, but could not find nix-darwin or darwin-rebuild after the command.

Did you restart your shell?

[Samasaur1]

I believe nix-info reported wrong macOS version, it should be macOS 11.7.8 (20G1351).

For some time after switching away from the 10.x numbering scheme, some system APIs would still return OS versions in that format for compatibility reasons, so that's not an issue.

Previously, I would occasionally hand edit /etc/nix/nix.conf, but now that it's a symbolic link to a file in /nix/store/ I should not hand edit the file any more. Am I right?

This is correct. Instead of editing it by hand, you would configure it with the nix options in your nix-darwin system configuration. For example, I have this in my system configuration:

nix.settings = {
  auto-optimise-store = true;
  experimental-features =
    [ "ca-derivations" "flakes" "nix-command" "repl-flake" ];
  keep-derivations = true;
  keep-outputs = true;
  substituters = [ "https://cache.garnix.io" ];
  trusted-public-keys =
    [ "cache.garnix.io:CTFPyKSLcx5RMJKfLo5EEPUObbA78b0YQ2DTCJXqr9g=" ];
};

which translates into this /etc/nix/nix.conf:

# WARNING: this file is generated from the nix.* options in
# your nix-darwin configuration. Do not edit it!
allowed-users = *
auto-optimise-store = true
build-users-group = nixbld
cores = 0
experimental-features = ca-derivations flakes nix-command repl-flake
extra-sandbox-paths = 
keep-derivations = true
keep-outputs = true
max-jobs = auto
require-sigs = true
sandbox = false
sandbox-fallback = false
substituters = https://cache.garnix.io https://cache.nixos.org/
trusted-public-keys = cache.garnix.io:CTFPyKSLcx5RMJKfLo5EEPUObbA78b0YQ2DTCJXqr9g= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
trusted-substituters = 
trusted-users = root

[HtwoO]

Did you restart your shell?

No. I realized I should have tried opening a new shell. I saw the following in the store:

macOS.CLI> ls -l /nix/store | rg 'nix-darwin'
dr-xr-xr-x  16 root  nixbld   512B  1  1  1970 6ir80yhfd7lhiqp78i43kq8hr947wcyg-nix-darwin/
macOS.CLI> ls -l /nix/store | rg --count 'darwin'
190
macOS.CLI> ls -l /nix/store | rg 'darwin-rebuild'
-r--r--r--   1 root  nixbld   2.7K  1  1  1970 310pjmvk23w2m7cr0kkx5hia7w5cgaq1-darwin-rebuild.drv
-r--r--r--   1 root  nixbld   0.7K  1  1  1970 bv7zmylsbdlzipw606ynsc51s424gb0y-darwin-rebuild.zsh-completions
dr-xr-xr-x   4 root  wheel    128B  1  1  1970 g3274z1798yh881a9n7f1sy3mkl8ifkh-darwin-rebuild/
-r--r--r--   1 root  nixbld   6.7K  1  1  1970 izq9m1f78vnrp908rkmrbh59765wdjpv-darwin-rebuild.sh
dr-xr-xr-x   4 root  wheel    128B  1  1  1970 rrbn6iyqkxriaa34x8v2l94iq81mchhi-darwin-rebuild/
-r--r--r--   1 root  nixbld   2.8K  1  1  1970 w5q0pckls3i3qf9jcj9w83r8nndhngqh-darwin-rebuild.drv

[HtwoO]

This is correct. Instead of editing it by hand, you would configure it with the nix options in your nix-darwin system configuration. For example, I have this in my system configuration:

Thank you for the confirmation and the reference configuration.

[emilazy]

Is there anything else we can help with here? I’d like the documentation to be approachable and address anything confusing in it. Unfortunately we’re probably not equipped to explain the flakes feature from scratch, but maybe we could introduce them a little, link to a general tutorial (although we’d need to decide which), and more clearly separate out the choice of flake vs. non‐flake configuration? It’d be useful to know what would have helped point you in the right direction as a beginner.

[HtwoO]

run the command again and found out it was much slower, not sure why

I figured this out by running the following:

nix --option substituters "https://mirror.iscas.ac.cn/nix-channels/store" \
    --option trusted-substituters "https://mirror.iscas.ac.cn/nix-channels/store" \
    --option trusted-users "$USER" run nix-darwin -- switch --flake ~/.config/nix

and it finished a lot quicker.

[HtwoO]

@emilazy

what is the relationship between configuration.nix and flake.nix

At least explain this a bit. I thought "are they referring to the same file there?".

With

mkdir -p ~/.config/nix-darwin
cd ~/.config/nix-darwin

in that section, I assumed ~/.config/nix-darwin is empty from scratch. Then in Migrating from an existing configuration.nix section the document says

Add the following to flake.nix in the same folder as configuration.nix

Is this second flake.nix referring to the same flake.nix in Getting started from scratch section? It's like referring to flake.nix or nix run nix-darwin -- switch --flake . without the cd ~/.config/nix-darwin.

Maybe provide a basic/working /path/to/configutration.nix example there.

[emilazy]

I appreciate the feedback, thank you! I’ll try and take a look at how we can make the documentation more clear here soon if someone else doesn’t beat me to it.