Merge fort-nix/nix-bitcoin#492: Improve flake

c8d5cb2405 examples: improve Flakes-based VM (Erik Arvstedt)
1e94e891b2 flake: move VM to separate file (Erik Arvstedt)
7233b054d9 flake: use new output format (Erik Arvstedt)

Pull request description:

ACKs for top commit:
  jonasnick:
    ACK c8d5cb2405

Tree-SHA512: ffc5525530a50e7664f9b081f68eb3d379f726b7f40133d1e874d41ce84814e44d1e57661803c0cf3aabae58b493cb60968b1dd75d9e4cbe5877f02c4cd6abc2

examples/README.md

@@ -1,8 +1,22 @@
-Examples
----
+## Examples
 
 The easiest way to try out nix-bitcoin is to use one of the provided examples.
 
+### Flakes-based quick start
+
+If you use a Flakes-enabled version of Nix, run the following command to start a minimal
+nix-bitcoin QEMU VM:
+```bash
+nix run github:fort-nix/nix-bitcoin/release
+```
+The VM (defined in [flake.nix](../flake.nix)) runs in the terminal and has `bitcoind`
+and `clightning` installed.\
+It leaves no traces (outside of `/nix/store`) on the host system.
+
+
+### More examples
+
+Clone this repo and enter the examples shell:
 ```bash
 git clone https://github.com/fort-nix/nix-bitcoin
 cd nix-bitcoin/examples/
@@ -79,7 +93,3 @@ The commands in `shell.nix` allow you to locally run the node in a VM or contain
 
 Flakes make it easy to include `nix-bitcoin` in an existing NixOS config.
 The [flakes example](./flakes/flake.nix) shows how to use `nix-bitcoin` as an input to a system flake.
-
-Run `nix run` or `nix run .#vm` from the nix-bitcoin root directory to start an example
-nix-bitcoin node VM.
-This command is defined by the nix-bitcoin flake (in [flake.nix](../flake.nix)).

examples/flakes/flake.nix

@@ -8,7 +8,7 @@
     nixosConfigurations.mynode = nix-bitcoin.inputs.nixpkgs.lib.nixosSystem {
       system = "x86_64-linux";
       modules = [
-        nix-bitcoin.nixosModule
+        nix-bitcoin.nixosModules.default
 
         # Optional:
         # Import the secure-node preset, an opinionated config to enhance security

examples/qemu-vm/minimal-vm.nix

@@ -0,0 +1,49 @@
+nix-bitcoin: pkgs: system:
+
+rec {
+  inherit (nix-bitcoin.inputs) nixpkgs;
+
+  mkVMScript = vm: pkgs.writers.writeBash "run-vm" ''
+    set -euo pipefail
+    export TMPDIR=$(mktemp -d /tmp/nix-bitcoin-vm.XXX)
+    trap "rm -rf $TMPDIR" EXIT
+    export NIX_DISK_IMAGE=$TMPDIR/nixos.qcow2
+    QEMU_OPTS="-smp $(nproc) -m 1500" ${vm}/bin/run-*-vm
+  '';
+
+  vm = (import "${nixpkgs}/nixos" {
+    inherit system;
+    configuration = { lib, ... }: {
+      imports = [
+        nix-bitcoin.nixosModules.default
+        "${nix-bitcoin}/modules/presets/secure-node.nix"
+      ];
+
+      nix-bitcoin.generateSecrets = true;
+      services.clightning.enable = true;
+      # For faster startup in offline VMs
+      services.clightning.extraConfig = "disable-dns";
+
+      nixpkgs.pkgs = pkgs;
+      virtualisation.graphics = false;
+      services.getty.autologinUser = "root";
+      nix.nixPath = [ "nixpkgs=${nixpkgs}" ];
+
+      services.getty.helpLine = lib.mkAfter ''
+
+        Welcome to nix-bitcoin!
+        To explore running services, try the following commands:
+        - nodeinfo
+        - systemctl status bitcoind
+        - systemctl status clightning
+      '';
+
+      # Power off VM when the user exits the shell
+      systemd.services."serial-getty@".preStop = ''
+        echo o >/proc/sysrq-trigger
+      '';
+    };
+  }).vm;
+
+  runVM = mkVMScript vm;
+}

flake.nix

@@ -24,11 +24,11 @@
           import ./pkgs { inherit pkgs pkgsUnstable; };
       };
 
-      overlay = final: prev: let
+      overlays.default = final: prev: let
         nbPkgs = lib.mkNbPkgs { inherit (final) system; pkgs = final; };
       in removeAttrs nbPkgs [ "pinned" "nixops19_09" "krops" ];
 
-      nixosModule = { config, pkgs, lib, ... }: {
+      nixosModules.default = { config, pkgs, lib, ... }: {
         imports = [ ./modules/modules.nix ];
 
         options = with lib; {
@@ -58,7 +58,7 @@
         };
       };
 
-      defaultTemplate = {
+      templates.default = {
         description = "Basic node template";
         path = ./examples/flakes;
       };
@@ -66,46 +66,16 @@
     } // (flake-utils.lib.eachSystem supportedSystems (system:
       let
         pkgs = nixpkgs.legacyPackages.${system};
-
         nbPkgs = self.lib.mkNbPkgs { inherit system pkgs; };
-
-        mkVMScript = vm: pkgs.writers.writeBash "run-vm" ''
-          set -euo pipefail
-          export TMPDIR=$(mktemp -d /tmp/nix-bitcoin-vm.XXX)
-          trap "rm -rf $TMPDIR" EXIT
-          export NIX_DISK_IMAGE=$TMPDIR/nixos.qcow2
-          QEMU_OPTS="-smp $(nproc) -m 1500" ${vm}/bin/run-*-vm
-        '';
       in rec {
         packages = flake-utils.lib.flattenTree (removeAttrs nbPkgs [
           "pinned" "modulesPkgs" "nixops19_09" "krops" "generate-secrets" "netns-exec"
         ]) // {
-          runVM = mkVMScript packages.vm;
-
-          # This is a simple demo VM.
-          # See ./examples/flakes/flake.nix on how to use nix-bitcoin with flakes.
-          vm = let
-            nix-bitcoin = self;
-          in
-            (import "${nixpkgs}/nixos" {
-              inherit system;
-              configuration = {
-                imports = [
-                  nix-bitcoin.nixosModule
-                  "${nix-bitcoin}/modules/presets/secure-node.nix"
-                ];
-
-                nix-bitcoin.generateSecrets = true;
-                services.clightning.enable = true;
-                # For faster startup in offline VMs
-                services.clightning.extraConfig = "disable-dns";
-
-                nixpkgs.pkgs = pkgs;
-                virtualisation.graphics = false;
-                services.getty.autologinUser = "root";
-                nix.nixPath = [ "nixpkgs=${nixpkgs}" ];
-              };
-            }).vm;
+          inherit (import ./examples/qemu-vm/minimal-vm.nix self pkgs system)
+            # A simple demo VM.
+            # See ./examples/flakes/flake.nix on how to use nix-bitcoin with flakes.
+            runVM
+            vm;
         };
 
         # Allow accessing the whole nested `nbPkgs` attrset (including `modulesPkgs`)
@@ -113,9 +83,9 @@
         # `packages` is not allowed to contain nested pkgs attrsets.
         legacyPackages = nbPkgs;
 
-        defaultApp = apps.vm;
+        apps = rec {
+          default = vm;
 
-        apps = {
           # Run a basic nix-bitcoin node in a VM
           vm = {
             type = "app";