init commit

modules/nixos/common/discovery.nix

@@ -0,0 +1,49 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+let
+  inherit (lib) mkOption mkIf types;
+in
+{
+  options.services.tty-ips = {
+    enable = mkOption {
+      type = types.bool;
+      default = false;
+      description = "Show interface IPs in TTY login using a dynamic issue file.";
+    };
+  };
+
+  config = mkIf config.services.tty-ips.enable {
+    systemd.services.tty-ips = {
+      description = "Generate /run/issue.dynamic with interface IPs";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network-online.target" ];
+      requires = [ "network-online.target" ];
+      before = [ "getty@tty1.service" ];
+
+      serviceConfig =
+        let
+          sw = "/run/current-system/sw/bin";
+        in
+        {
+          Type = "oneshot";
+          ExecStart = pkgs.writeShellScript "tty-ips-generate" ''
+            echo "Welcome to NixOS!" > /run/issue.dynamic
+            echo "" >> /run/issue.dynamic
+            echo "IP Addresses:" >> /run/issue.dynamic
+            ${sw}/ip -brief addr show ygg0 | ${sw}/awk '{print "  " $3}v' | ${pkgs.qrencode}/bin/qrencode -t ANSIUTF8 >> /run/issue.dynamic
+            echo "" >> /run/issue.dynamic
+          '';
+        };
+    };
+
+    services.getty.extraArgs = [
+      "--issue-file"
+      "/run/issue.dynamic"
+    ];
+  };
+}