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|
/*
Manages the things that are needed for a traditional nix-channel based
configuration to work.
See also
- ./nix.nix
- ./nix-flakes.nix
*/
{ config, lib, ... }:
let
inherit (lib)
mkDefault
mkIf
mkOption
stringAfter
types
;
cfg = config.nix;
in
{
options = {
nix = {
channel = {
enable = mkOption {
description = lib.mdDoc ''
Whether the `nix-channel` command and state files are made available on the machine.
The following files are initialized when enabled:
- `/nix/var/nix/profiles/per-user/root/channels`
- `/root/.nix-channels`
- `$HOME/.nix-defexpr/channels` (on login)
Disabling this option will not remove the state files from the system.
'';
type = types.bool;
default = true;
};
};
nixPath = mkOption {
type = types.listOf types.str;
default =
if cfg.channel.enable
then [
"nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos"
"nixos-config=/etc/nixos/configuration.nix"
"/nix/var/nix/profiles/per-user/root/channels"
]
else [ ];
defaultText = ''
if nix.channel.enable
then [
"nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos"
"nixos-config=/etc/nixos/configuration.nix"
"/nix/var/nix/profiles/per-user/root/channels"
]
else [];
'';
description = lib.mdDoc ''
The default Nix expression search path, used by the Nix
evaluator to look up paths enclosed in angle brackets
(e.g. `<nixpkgs>`).
'';
};
};
system = {
defaultChannel = mkOption {
internal = true;
type = types.str;
default = "https://nixos.org/channels/nixos-unstable";
description = lib.mdDoc "Default NixOS channel to which the root user is subscribed.";
};
};
};
config = mkIf cfg.enable {
environment.extraInit =
mkIf cfg.channel.enable ''
if [ -e "$HOME/.nix-defexpr/channels" ]; then
export NIX_PATH="$HOME/.nix-defexpr/channels''${NIX_PATH:+:$NIX_PATH}"
fi
'';
environment.extraSetup = mkIf (!cfg.channel.enable) ''
rm --force $out/bin/nix-channel
'';
# NIX_PATH has a non-empty default according to Nix docs, so we don't unset
# it when empty.
environment.sessionVariables = {
NIX_PATH = cfg.nixPath;
};
nix.settings.nix-path = mkIf (! cfg.channel.enable) (mkDefault "");
system.activationScripts.nix-channel = mkIf cfg.channel.enable
(stringAfter [ "etc" "users" ] ''
# Subscribe the root user to the NixOS channel by default.
if [ ! -e "/root/.nix-channels" ]; then
echo "${config.system.defaultChannel} nixos" > "/root/.nix-channels"
fi
'');
};
}
|