try fix

nixos/arion/arion-compose.nix

@@ -1,50 +1,20 @@
-
-/*
-
-  DISCLAIMER
-
-  This uses a somewhat hidden feature in NixOS, which is the
-  "runner". It's a script that's available on systemd services
-  that lets you run the service independently from systemd.
-  However, it was clearly not intended for public consumption
-  so please use it with care.
-  It does not support all features of systemd so you are on
-  your own if you use it in production.
-
-  One known issue is that the script does not respond to docker's
-  SIGTERM shutdown signal.
-
- */
-
+{ pkgs, ... }:
 {
-  project.name = "nixos-unit";
-  services.webserver = { config, pkgs, ... }: {
+  project.name = "webapp";
+  services = {
 
-    nixos.configuration = {config, lib, options, pkgs, ...}: {
-      boot.isContainer = true;
-      services.nginx = {
-        enable = true;
-        virtualHosts.localhost.root = "${pkgs.nix.doc}/share/doc/nix/manual";
-      } // lib.optionalAttrs (options?services.nginx.stateDir) {
-        # Work around a problem in NixOS 20.03
-        stateDir = "/var/lib/nginx";
-      };
-      system.build.run-nginx = pkgs.writeScript "run-nginx" ''
-        #!${pkgs.bash}/bin/bash
-        PATH='${config.systemd.services.nginx.environment.PATH}'
-        echo nginx:x:${toString config.users.users.nginx.uid}:${toString config.users.groups.nginx.gid}:nginx web server user:/var/empty:/bin/sh >>/etc/passwd
-        echo nginx:x:${toString config.users.groups.nginx.gid}:nginx >>/etc/group
-        echo 'nobody:x:65534:65534:Unprivileged account do not use:/var/empty:/run/current-system/sw/bin/nologin' >>/etc/passwd
-        echo 'nogroup:x:65534:' >>/etc/group
-        mkdir -p /var/log/nginx /run/nginx/ /var/cache/nginx /var/lib/nginx/{,logs,proxy_temp,client_body_temp,fastcgi_temp,scgi_temp,uwsgi_temp} /tmp/nginx_client_body
-        chown nginx /var/log/nginx /run/nginx/ /var/cache/nginx /var/lib/nginx/{,logs,proxy_temp,client_body_temp,fastcgi_temp,scgi_temp,uwsgi_temp} /tmp/nginx_client_body
-        ${config.systemd.services.nginx.runner}
-      '';
-    };
-    service.command = [ config.nixos.build.run-nginx ];
+    webserver = {
+      image.enableRecommendedContents = true;
       service.useHostStore = true;
+      service.command = [ "sh" "-c" ''
+                  cd "$$WEB_ROOT"
+                  ${pkgs.python3}/bin/python -m http.server
+                '' ];
       service.ports = [
-      "8009:80" # host:container
+        "8009:8000" # host:container
       ];
+      service.environment.WEB_ROOT = "${pkgs.nix.doc}/share/doc/nix/manual";
+      service.stop_signal = "SIGINT";
+    };
   };
 }

nixos/linux.nix

@@ -110,8 +110,6 @@ in {
     defaultNetwork.settings.dns_enabled = true;
   };
 
-  virtualisation.arion.backend.type = "podman-socket";
-
   virtualisation.oci-containers = {
     backend = "docker";