Disable btrbk logging

btrbk can always be invoked via the systemd service, hence journalctl
should be used instead.

hosts/aragorn/default.nix

@@ -149,8 +149,6 @@
     onCalendar = "hourly";
     settings = {
       timestamp_format = "long";
-      transaction_syslog = "cron";
-      transaction_log = "/var/log/btrbk.log";
       lockfile = "/var/lib/btrbk/btrbk.lock";
       cache_dir = "/var/cache/btrbk";
       btrfs_commit_delete = "yes";

nixos/common.nix

@@ -39,6 +39,9 @@ in
 
   nix.registry = registryInputs // { dotfiles.flake = inputs.self; };
 
+  # NOTE: on Darwin, nix.optimise.user needs to be specified
+  # nix.optimise.automatic = true;
+
   nix.settings = {
     auto-allocate-uids = true;
     auto-optimise-store = true;

nixos/guix.nix

@@ -13,7 +13,11 @@ lib.mkIf cfg.enable {
     stateDir = "/gnu/var";
     gc = {
       enable = true;
-      extraArgs = [ "--optimize" "--delete-generations=14d" ];
+      extraArgs = [
+        "--optimize"
+        "--vacuum-database"
+        "--delete-generations=14d"
+      ];
       dates = lib.mkDefault config.nix.gc.dates;
     };
   };