Remote activation

README.md

@@ -2,16 +2,21 @@
 
 # nixos-flake
 
-A [flake-parts](https://flake.parts/) module to unify [NixOS](https://nixos.org/manual/nixos/stable/) + [nix-darwin](https://github.com/LnL7/nix-darwin) + [home-manager] configuration in a single flake, while providing a consistent interface (and enabling common modules) for both Linux and macOS.
+A [flake-parts](https://flake.parts/) module to unify [NixOS](https://nixos.org/manual/nixos/stable/) + [nix-darwin](https://github.com/LnL7/nix-darwin) + [home-manager] configuration in a single flake, while providing a consistent interface (and enabling common modules) for both Linux and macOS. For motivation, see https://community.flake.parts/nixos-flake
 
-Why? [See here](https://github.com/srid/nixos-flake/discussions/40#discussioncomment-7542918)
 
 [home-manager]: https://github.com/nix-community/home-manager
 
+
+
 ## Getting Started
 
 https://community.flake.parts/nixos-flake/start
 
+## Examples
+
+https://community.flake.parts/nixos-flake/examples
+
 ## Discussion
 
 To discuss the project, post in [our Zulip](https://nixos.zulipchat.com/#narrow/stream/413948-nixos) (preferred) or in [Github Discussions](https://github.com/srid/nixos-flake/discussions).

activate/activate.nu

@@ -0,0 +1,70 @@
+use std log
+use nixos-flake.nu getData  # This module is generated in Nix
+
+let CURRENT_HOSTNAME = (hostname | str trim)
+
+# Activate system configuration of local machine
+#
+# To activate a remote machine, use run with subcommands: `host <hostname>`
+def main [] {
+    main host ($CURRENT_HOSTNAME)
+}
+
+# Activate system configuration of the given host
+def 'main host' [
+  host: string # Hostname to activate (must match flake.nix name)
+] {
+    let data = getData
+    if $host not-in $data.nixos-flake-configs {
+        log error $"Host '($host)' not found in flake. Available hosts=($data.nixos-flake-configs | columns)"
+        exit 1
+    }
+    let hostData = $data.nixos-flake-configs 
+        | get $host
+        | insert "flake" $"($data.cleanFlake)#($host)"
+
+    log info $"(ansi grey)currentSystem=($data.system) currentHost=(ansi green_bold)($CURRENT_HOSTNAME)(ansi grey) targetHost=(ansi green_reverse)($host)(ansi reset)(ansi grey) hostData=($hostData)(ansi reset)"
+
+    let runtime = {
+        local: ($CURRENT_HOSTNAME == $host)
+        darwin: ($hostData.outputs.system in ["aarch64-darwin" "x86_64-darwin"])
+    }
+
+    if $runtime.local {
+        # Since the user asked to activate current host, do so.
+        log info $"Activating (ansi purple)locally(ansi reset)"
+        if $runtime.darwin {
+            log info $"(ansi blue_bold)>>>(ansi reset) darwin-rebuild switch --flake ($hostData.flake) ($hostData.outputs.nixArgs | str join)"
+            darwin-rebuild switch --flake $hostData.flake ...$hostData.outputs.nixArgs 
+        } else {
+            log info $"(ansi blue_bold)>>>(ansi reset) nixos-rebuild switch --flake ($hostData.flake) ($hostData.outputs.nixArgs | str join) --use-remote-sudo "
+            nixos-rebuild switch --flake $hostData.flake ...$hostData.outputs.nixArgs --use-remote-sudo
+        }
+    } else {
+        # Remote activation request, so copy the flake and the necessary inputs
+        # and then activate over SSH.
+        if $hostData.sshTarget == null {
+            log error $"sshTarget not found in host data for ($host). Add `nixos-flake.sshTarget = \"user@hostname\";` to your configuration."
+            exit 1
+        }
+        log info $"Activating (ansi purple_reverse)remotely(ansi reset) on ($hostData.sshTarget)"
+        nix copy ($data.cleanFlake) --to ($"ssh-ng://($hostData.sshTarget)")
+
+        $hostData.outputs.overrideInputs | transpose key value | each { |input|
+            log info $"Copying input ($input.key) to ($hostData.sshTarget)"
+            log info $"(ansi blue_bold)>>>(ansi reset) nix copy ($input.value) --to ($"ssh-ng://($hostData.sshTarget)")"
+            nix copy ($input.value) --to ($"ssh-ng://($hostData.sshTarget)")
+        }
+
+        # We re-run this script, but on the remote host.
+        log info $'(ansi blue_bold)>>>(ansi reset) ssh -t ($hostData.sshTarget) nix --extra-experimental-features '"nix-command flakes"' run ($hostData.outputs.nixArgs | str join) $"($data.cleanFlake)#activate" host ($host)'
+        ssh -t $hostData.sshTarget nix --extra-experimental-features '"nix-command flakes"' run ...$hostData.outputs.nixArgs $"($data.cleanFlake)#activate host ($host)"
+    }
+}
+
+# TODO: Implement this, resolving https://github.com/srid/nixos-flake/issues/18
+def 'main home' [] {
+    log error "Home activation not yet supported; use .#activate-home instead"
+    exit 1
+}
+

activate/default.nix

@@ -0,0 +1,61 @@
+{ self, inputs', pkgs, lib, system, ... }:
+
+let
+  # Workaround https://github.com/NixOS/nix/issues/8752
+  cleanFlake = lib.cleanSourceWith {
+    name = "nixos-flake-activate-flake";
+    src = self;
+  };
+  nixos-flake-configs = lib.mapAttrs (name: value: value.config.nixos-flake) (self.nixosConfigurations or { } // self.darwinConfigurations or { });
+  data = {
+    nixos-flake-configs = nixos-flake-configs;
+    system = system;
+    cleanFlake = cleanFlake;
+  };
+  dataFile = pkgs.writeTextFile {
+    name = "nixos-flake-activate-data";
+    text = ''
+      ${builtins.toJSON data}
+    '';
+  };
+  nixosFlakeNuModule = pkgs.writeTextFile {
+    name = "nixos-flake.nu";
+    text = ''
+      export def getData [] {
+        open ${dataFile} | from json
+      }
+    '';
+  };
+  runtimeInputs =
+    # TODO: better way to check for nix-darwin availability
+    if pkgs.stdenv.isDarwin && lib.hasAttr "nix-darwin" inputs' then [
+      inputs'.nix-darwin.packages.default # Provides darwin-rebuild
+    ] else [
+      pkgs.nixos-rebuild
+    ];
+  nixNuModule = pkgs.writeTextFile {
+    name = "nix.nu";
+    text = ''
+      use std *
+      let bins = '${builtins.toJSON (builtins.map (p: "${p}/bin") runtimeInputs)}' | from json
+      if $bins != [] {
+        log debug $"Adding runtime inputs to PATH: ($bins)"
+        path add ...$bins
+      }
+    '';
+  };
+  nuPackage = pkgs.runCommandNoCC "nushell"
+    {
+      meta.mainProgram = "activate.nu";
+    } ''
+    mkdir -p $out/bin
+    cd $out/bin
+    echo "#!${pkgs.nushell}/bin/nu" >> activate.nu
+    cat ${nixNuModule} >> activate.nu
+    # echo 'print $"PATH = ($env.PATH)"' >> activate.nu
+    cat ${./activate.nu} >> activate.nu
+    chmod a+x activate.nu
+    cp ${nixosFlakeNuModule} nixos-flake.nu
+  '';
+in
+nuPackage

doc/activate.md

@@ -0,0 +1,46 @@
+
+# Activation
+
+`nixos-flake` provides the `.#activate` flake app that can be used in place of `nixos-rebuild` (if using NixOS) and `darwin-rebuild` (if using `nix-darwin`).
+
+In addition, it can also activate the system over SSH -- see next section.
+
+```sh
+nix run .#activate
+```
+
+Usually, you'd make this your default package, so as to be able to use `nix run`. In `flake.nix`:
+
+```nix
+# In perSystem
+{
+    packages.default = self'.packages.activate
+}
+```
+
+
+{#remote}
+## Remote Activation
+
+You can use `nixos-flake` as a lightweight alternative to the various deployment tools such as `deploy-rs` and `colmena`. The `.#activate` app takes the hostname as an argument. If you set the `nixos-flake.sshTarget` option in your NixOS or nix-darwin configuration, it will run activation over the SSH connection.
+
+Add the following to your configuration -- `nixosConfigurations.myhost` or `darwinConfigurations.myhost` (depending on the platform):
+
+```nix
+{
+    nixos-flake.sshTarget = "myuser@myhost";
+}
+```
+
+Then, you will be able to run the following to deploy to `myhost` from any machine:
+
+```sh
+nix run .#activate host myhost
+```
+
+### Non-goals
+
+Remote activation doesn't seek to replace other deployment tools, and as such doesn't provide features like rollbacks. It is meant for simple deployment use cases. 
+
+>[!NOTE] Future
+> It is possible however that `nixos-flake` can grow to support more sophisticated deployment capabilities

doc/guide.md

@@ -2,4 +2,5 @@
 # Guide
 
 - [[templates]]#
+- [[activate]]#
 - [[module-outputs]]#

doc/index.md

@@ -3,12 +3,26 @@ short-title: nixos-flake ❄️
 template:
   sidebar:
     collapsed: true
+emanote:
+  folder-folgezettel: false
 ---
 
 # Managing OS and home configurations using `nixos-flake`
 
 [nixos-flake](https://github.com/srid/nixos-flake) a [flake-parts](https://flake.parts/) module to unify [NixOS](https://nixos.org/manual/nixos/stable/) + [nix-darwin](https://github.com/LnL7/nix-darwin) + [home-manager] configuration in a single flake, while providing a consistent interface (and enabling common modules) for both Linux and macOS.
 
+## Why?
+
+nixos-flake provides the following features:
+
+- [[activate]]: An `.#activate` flake app that works both on macOS and NixOS.
+  - `.#activate` can also *remotely* activate machines (be it macOS or NixOS) over SSH.
+- All NixOS/ nix-darwin/ home-manager modules receive `specialArgs` which includes all the information in the top-level flake.
+  - This enables those modules to be aware of the flake inputs, for instance.
+- A `.#update` flake app to update the primary inputs (which can be overriden)
+
+## Getting Started
+
 See: [[start]]# and [[guide]]#. For examples, see [[examples]]#
 
 [home-manager]: https://github.com/nix-community/home-manager

doc/module-outputs.md

@@ -4,16 +4,19 @@ Importing the `nixos-flake` flake-parts module will autowire the following flake
 
 | Name                         | Description                                    |
 | ---------------------------- | ---------------------------------------------- |
-| `nixos-flake.lib`             | Functions `mkLinuxSystem`, `mkMacosSystem` and `mkHomeConfiguration` |
-| `nixosModules.home-manager`  | Home-manager setup module for NixOS            |
-| `darwinModules_.home-manager` | Home-manager setup module for Darwin           |
-| `packages.update`            | Flake app to update key flake inputs            |
-| `packages.activate`          | Flake app to build & activate the system       |
-| `packages.activate-home`          | Flake app to build & activate the `homeConfigurations` for current user       |
+| **nixos-flake.lib**             | Functions `mkLinuxSystem`, `mkMacosSystem` and `mkHomeConfiguration` |
+| **nixosModules.home-manager**  | Home-manager setup module for NixOS            |
+| **darwinModules_.home-manager**[^und] | Home-manager setup module for Darwin           |
+| **packages.update**            | Flake app to update key flake inputs            |
+| [[activate\|packages.activate]]          | Flake app to build & activate the system (locally or remotely over SSH)       |
+| **packages.activate-home**[^home]          | Flake app to build & activate the `homeConfigurations` for current user       |
 
 In addition, all of your NixOS/nix-darwin/home-manager modules implicitly receive the following `specialArgs`:
 
 - `flake@{self, inputs, config}` (`config` is from flake-parts')
 - `rosettaPkgs` (if on darwin)
 
-**NOTE**: The module API is open to change. [All feedback welcome](https://github.com/srid/nixos-flake/issues/new).
+
+[^home]: This will soon be removed in favour of the [[activate|activate app]]. See https://github.com/srid/nixos-flake/issues/18
+
+[^und]: Why the underscore in `darwinModules_`? This is to workaround a segfault with flake-parts. See https://github.com/srid/nixos-config/issues/31

flake-module.nix

@@ -18,8 +18,8 @@ let
 in
 {
   options = {
-    perSystem = mkPerSystemOption
-      ({ config, self', inputs', pkgs, system, ... }: {
+    perSystem =
+      mkPerSystemOption ({ config, self', inputs', pkgs, system, ... }: {
         options.nixos-flake = lib.mkOption {
           default = { };
           type = types.submodule {
@@ -47,40 +47,8 @@ in
                 '';
               };
 
-            activate =
-              if hasNonEmptyAttr [ "darwinConfigurations" ] self || hasNonEmptyAttr [ "nixosConfigurations" ] self
-              then
-                pkgs.writeShellApplication
-                  {
-                    name = "activate";
-                    text =
-                      # TODO: Replace with deploy-rs or (new) nixinate
-                      if system == "aarch64-darwin" || system == "x86_64-darwin" then
-                        let
-                          # This is used just to pull out the `darwin-rebuild` script.
-                          # See also: https://github.com/LnL7/nix-darwin/issues/613
-                          emptyConfiguration = self.nixos-flake.lib.mkMacosSystem { nixpkgs.hostPlatform = system; };
-                        in
-                        ''
-                          HOSTNAME=$(hostname -s)
-                          set -x
-                          ${emptyConfiguration.system}/sw/bin/darwin-rebuild \
-                            switch \
-                            --flake "path:${self}#''${HOSTNAME}" \
-                            "$@"
-                        ''
-                      else
-                        ''
-                          HOSTNAME=$(hostname -s)
-                          set -x
-                          ${lib.getExe pkgs.nixos-rebuild} \
-                            switch \
-                            --flake "path:${self}#''${HOSTNAME}" \
-                            --use-remote-sudo \
-                            "$@"
-                        '';
-                  }
-              else null;
+            # New-style activate app that can also activately remotely over SSH.
+            activate = import ./activate { inherit self inputs' pkgs lib system; };
 
             activate-home =
               if hasNonEmptyAttr [ "homeConfigurations" ] self || hasNonEmptyAttr [ "legacyPackages" system "homeConfigurations" ] self
@@ -104,6 +72,7 @@ in
 
   config = {
     flake = {
+      nixosModules.nixosFlake = ./nix/nixos-module.nix;
       # Linux home-manager module
       nixosModules.home-manager = {
         imports = [
@@ -115,6 +84,8 @@ in
           })
         ];
       };
+
+      darwinModules_.nixosFlake = ./nix/nixos-module.nix;
       # macOS home-manager module
       # This is named with an underscope, because flake-parts segfaults otherwise!
       # See https://github.com/srid/nixos-config/issues/31
@@ -134,12 +105,18 @@ in
         mkLinuxSystem = mod: inputs.nixpkgs.lib.nixosSystem {
           # Arguments to pass to all modules.
           specialArgs = specialArgsFor.nixos;
-          modules = [ mod ];
+          modules = [
+            self.nixosModules.nixosFlake
+            mod
+          ];
         };
 
         mkMacosSystem = mod: inputs.nix-darwin.lib.darwinSystem {
           specialArgs = specialArgsFor.darwin;
-          modules = [ mod ];
+          modules = [
+            self.darwinModules_.nixosFlake
+            mod
+          ];
         };
 
         mkHomeConfiguration = pkgs: mod: inputs.home-manager.lib.homeManagerConfiguration {