diff --git a/hosts/skydick/default.nix b/hosts/skydick/default.nix
index c03bc35..b9a3c18 100644
--- a/hosts/skydick/default.nix
+++ b/hosts/skydick/default.nix
@@ -219,6 +219,7 @@
     nvme-cli
 
     # Monitoring
+    btop
     iotop
     iftop
     smartmontools
diff --git a/modules/common.nix b/modules/common.nix
index 6d30169..be76f86 100644
--- a/modules/common.nix
+++ b/modules/common.nix
@@ -8,6 +8,12 @@
     experimental-features = [ "nix-command" "flakes" ];
     auto-optimise-store = true;
     trusted-users = [ "root" "ldx" ];
+    substituters = [
+      "https://mirrors.tuna.tsinghua.edu.cn/nix-channels/store"
+      "https://cache.nixos.org/"
+    ];
+    connect-timeout = 5;
+    stalled-download-timeout = 15;
   };
 
   environment.systemPackages = with pkgs; [