nixos/ollama: add options to bypass sandboxing

nixos/modules/services/misc/ollama.nix

@@ -21,6 +21,8 @@ in
         example = "/home/foo";
         description = ''
           The home directory that the ollama service is started in.
+
+          See also `services.ollama.writablePaths` and `services.ollama.sandbox`.
         '';
       };
       models = lib.mkOption {
@@ -29,6 +31,37 @@ in
         example = "/path/to/ollama/models";
         description = ''
           The directory that the ollama service will read models from and download new models to.
+
+          See also `services.ollama.writablePaths` and `services.ollama.sandbox`
+          if downloading models or other mutation of the filesystem is required.
+        '';
+      };
+      sandbox = lib.mkOption {
+        type = types.bool;
+        default = true;
+        example = false;
+        description = ''
+          Whether to enable systemd's sandboxing capabilities.
+
+          This sets [`DynamicUser`](
+          https://www.freedesktop.org/software/systemd/man/latest/systemd.exec.html#DynamicUser=
+          ), which runs the server as a unique user with read-only access to most of the filesystem.
+
+          See also `services.ollama.writablePaths`.
+        '';
+      };
+      writablePaths = lib.mkOption {
+        type = types.listOf types.str;
+        default = [ ];
+        example = [ "/home/foo" "/mnt/foo" ];
+        description = ''
+          Paths that the server should have write access to.
+
+          This sets [`ReadWritePaths`](
+          https://www.freedesktop.org/software/systemd/man/latest/systemd.exec.html#ReadWritePaths=
+          ), which allows specified paths to be written to through the default sandboxing.
+
+          See also `services.ollama.sandbox`.
         '';
       };
       listenAddress = lib.mkOption {
@@ -59,8 +92,8 @@ in
         type = types.attrsOf types.str;
         default = { };
         example = {
-          HOME = "/tmp";
           OLLAMA_LLM_LIBRARY = "cpu";
+          HIP_VISIBLE_DEVICES = "0,1";
         };
         description = ''
           Set arbitrary environment variables for the ollama service.
@@ -87,7 +120,8 @@ in
         ExecStart = "${lib.getExe ollamaPackage} serve";
         WorkingDirectory = cfg.home;
         StateDirectory = [ "ollama" ];
-        DynamicUser = true;
+        DynamicUser = cfg.sandbox;
+        ReadWritePaths = cfg.writablePaths;
       };
     };