Initial stab at a custom image

May not work, haven't tested it, need to switch systems

README.md

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+# nixos-systems
+
+These are the system definitions for various systems being run by Gleipnir Technology.
+
+## From Zero
+
+Hat tip to [the negation](https://thenegation.com/posts/nixos-do-colmena/) for some ideas here.
+
+Build a custom image for Digital Ocean:
+
+```
+nix-build digitalocean/custom-image.nix
+```

digitalocean/custom-image.nix

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+let
+  ## Pin the latest NixOS stable (nixos-25.05) release:
+  nixpkgs = builtins.fetchTarball {
+    url = "https://github.com/NixOS/nixpkgs/archive/refs/tags/25.05.tar.gz";
+    sha256 = "sha256:0q96nxw7jg9l9zlpa3wkma5xzmgkdnnajapwhgb2fk2ll224rgs1";
+  };
+
+  ## Import nixpkgs:
+  pkgs = import nixpkgs { };
+
+  ## Prepare the NixOS configuration:
+  config = {
+    imports = [
+      "${nixpkgs}/nixos/modules/virtualisation/digital-ocean-image.nix"
+    ];
+  };
+in
+(pkgs.nixos config).digitalOceanImage