building Nix...
building the system configuration...
error: Package ‘nextcloud-18.0.10’ in /nix/store/6dra63mqv1piw23gxwslh0y0sbnsd44f-nixos-20.09.2205.65c9cc79f1d/nixos/pkgs/servers/nextcloud/default.nix:21 is marked as insecure, refusing to evaluate.


Known issues:
 - Nextcloud version 18.0.10 is EOL

You can install it anyway by whitelisting this package, using the
following methods:

a) To temporarily allow all insecure packages, you can use an environment
   variable for a single invocation of the nix tools:

     $ export NIXPKGS_ALLOW_INSECURE=1

b) for `nixos-rebuild` you can add ‘nextcloud-18.0.10’ to
   `nixpkgs.config.permittedInsecurePackages` in the configuration.nix,
   like so:

     {
       nixpkgs.config.permittedInsecurePackages = [
         "nextcloud-18.0.10"
       ];
     }

c) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
   ‘nextcloud-18.0.10’ to `permittedInsecurePackages` in
   ~/.config/nixpkgs/config.nix, like so:

     {
       permittedInsecurePackages = [
         "nextcloud-18.0.10"
       ];
     }


(use '--show-trace' to show detailed location information)