diff --git a/config/AutoUpdateSigned.nix b/config/AutoUpdateSigned.nix
index cfa7d0e..835cc26 100644
--- a/config/AutoUpdateSigned.nix
+++ b/config/AutoUpdateSigned.nix
@@ -4,7 +4,6 @@
 # to prevent unathorized changes to hosts.
 {
   config,
-  const,
   lib,
   pkgs,
   secret,
@@ -40,7 +39,7 @@ in
       script = ''
         pushd /tmp
         rm -rf ./nixos
-        git clone --depth=1 --single-branch --branch=main ${const.url} ./nixos
+        git clone --depth=1 --single-branch --branch=main ${config.const.url} ./nixos
         pushd ./nixos
         git verify-commit HEAD && git fsck || {
           echo "Verification failed."
diff --git a/flake.nix b/flake.nix
index 2442cbf..6a72eeb 100644
--- a/flake.nix
+++ b/flake.nix
@@ -122,13 +122,6 @@
     let
       lib = nixpkgs.lib;
 
-      const = {
-        droidStateVersion = "24.05";
-        stateVersion = "24.11";
-        timeZone = "Europe/Moscow";
-        url = "https://git.voronind.com/voronind/nix.git";
-      };
-
       __findFile = _: p: ./${p};
 
       ls =
@@ -175,9 +168,6 @@
                   # Make a device hostname match the one from this config.
                   { networking.hostName = hostname; }
 
-                  # Specify current release version.
-                  { system.stateVersion = const.stateVersion; }
-
                   # Add Home Manager module.
                   home-manager.nixosModules.home-manager
 
@@ -203,7 +193,6 @@
                 {
                   inherit
                     __findFile
-                    const
                     inputs
                     pkgsJobber
                     pkgsMaster
@@ -258,7 +247,6 @@
           extraSpecialArgs = {
             inherit
               __findFile
-              const
               inputs
               pkgsMaster
               pkgsUnstable
diff --git a/home/Android.nix b/home/Android.nix
index 5bb0b53..58c52e8 100644
--- a/home/Android.nix
+++ b/home/Android.nix
@@ -2,7 +2,6 @@
 {
   __findFile,
   config,
-  const,
   inputs,
   lib,
   pkgs,
@@ -28,8 +27,8 @@ in
   config = lib.mkIf cfg.enable {
     environment.packages = package.core;
     nix.extraOptions = "experimental-features = nix-command flakes pipe-operators";
-    system.stateVersion = const.droidStateVersion;
-    time.timeZone = const.timeZone;
+    system.stateVersion = config.const.droidStateVersion;
+    time.timeZone = config.const.timeZone;
     terminal = { inherit (android) font colors; };
     home-manager.config = stylix // {
       programs = with programs; core;
@@ -37,7 +36,7 @@ in
       home = {
         inherit (env) sessionVariables;
         inherit file;
-        stateVersion = const.droidStateVersion;
+        stateVersion = config.const.droidStateVersion;
       };
     };
   };
diff --git a/home/NixOs.nix b/home/NixOs.nix
index 1bfbf39..5e8ae89 100644
--- a/home/NixOs.nix
+++ b/home/NixOs.nix
@@ -2,7 +2,6 @@
 {
   __findFile,
   config,
-  const,
   lib,
   pkgs,
   util,
@@ -36,7 +35,7 @@ in
         // {
           ${user.username} = {
             home = {
-              inherit (const) stateVersion;
+              inherit (config.const) stateVersion;
               inherit (env) sessionVariables;
               inherit (user) username homeDirectory;
               inherit file;
diff --git a/host/x86_64-linux/home/Const.nix b/host/x86_64-linux/home/Const.nix
new file mode 100644
index 0000000..3281c6a
--- /dev/null
+++ b/host/x86_64-linux/home/Const.nix
@@ -0,0 +1,7 @@
+{ ... }: {
+  config.const.host = {
+    domain = "voronind.com";
+    sslCertificate = "/etc/letsencrypt/live/voronind.com/fullchain.pem";
+    sslCertificateKey = "/etc/letsencrypt/live/voronind.com/privkey.pem";
+  };
+}
diff --git a/host/x86_64-linux/home/Davis.nix b/host/x86_64-linux/home/Davis.nix
index 2914321..5d0b967 100644
--- a/host/x86_64-linux/home/Davis.nix
+++ b/host/x86_64-linux/home/Davis.nix
@@ -8,10 +8,7 @@ in
     adminPasswordFile = "${storage}/Password";
     appSecretFile = "${storage}/Secret";
     hostname = "dav.voronind.com";
-    nginx = {
-      sslCertificate = "/etc/letsencrypt/live/voronind.com/fullchain.pem";
-      sslCertificateKey = "/etc/letsencrypt/live/voronind.com/privkey.pem";
-    };
+    nginx = { };
     mail = {
       dsnFile = "${storage}/Dsn";
       inviteFromAddress = "noreply@voronind.com";
diff --git a/host/x86_64-linux/home/Jobber.nix b/host/x86_64-linux/home/Jobber.nix
index 695b79b..465725a 100644
--- a/host/x86_64-linux/home/Jobber.nix
+++ b/host/x86_64-linux/home/Jobber.nix
@@ -1,7 +1,6 @@
 # Use `nixos-container login jobber` as root and empty pw.
 {
   __findFile,
-  const,
   lib,
   pkgsJobber,
   poetry2nixJobber,
@@ -48,7 +47,7 @@ in
       in
       {
         boot.isContainer = true;
-        system.stateVersion = const.stateVersion;
+        system.stateVersion = "24.11";
         users = {
           users.root.password = "";
           mutableUsers = false;
diff --git a/host/x86_64-linux/home/Network.nix b/host/x86_64-linux/home/Network.nix
index 91dba4b..ab2132c 100644
--- a/host/x86_64-linux/home/Network.nix
+++ b/host/x86_64-linux/home/Network.nix
@@ -3,7 +3,6 @@
 # fd09:8d46:b26::/48 - ULA.
 {
   config,
-  const,
   lib,
   util,
   ...
@@ -120,7 +119,7 @@ in
           PoolOffset = 100;
           PoolSize = 150;
           ServerAddress = "${internal}/24";
-          Timezone = const.timeZone;
+          Timezone = config.const.timeZone;
           UplinkInterface = wan;
         };
       };
diff --git a/host/x86_64-linux/home/nginx/Davis.nix b/host/x86_64-linux/home/nginx/Davis.nix
index c18d785..a32a617 100644
--- a/host/x86_64-linux/home/nginx/Davis.nix
+++ b/host/x86_64-linux/home/nginx/Davis.nix
@@ -1,15 +1,14 @@
-{ lib, ... }:
+{ config, ... }:
 {
-  "dav.voronind.com" = {
-    sslCertificate = "/etc/letsencrypt/live/voronind.com/fullchain.pem";
-    sslCertificateKey = "/etc/letsencrypt/live/voronind.com/privkey.pem";
-    onlySSL = lib.mkForce true;
+  "dav.${config.const.host.domain}" = {
+    inherit (config.const.host) sslCertificate sslCertificateKey;
     locations."/".extraConfig = ''
       allow 10.0.0.0/8;
       allow fd09:8d46:b26::/48;
       deny all;
     '';
     extraConfig = ''
+      listen 443 ssl;
       include /etc/letsencrypt/conf/options-ssl-nginx.conf;
       ssl_dhparam /etc/letsencrypt/conf/ssl-dhparams.pem;
     '';
diff --git a/host/x86_64-linux/home/nginx/Deluge.nix b/host/x86_64-linux/home/nginx/Deluge.nix
index 4978671..ad5c154 100644
--- a/host/x86_64-linux/home/nginx/Deluge.nix
+++ b/host/x86_64-linux/home/nginx/Deluge.nix
@@ -1,6 +1,6 @@
-{ ... }:
+{ config, ... }:
 {
-  "download.voronind.com".extraConfig = ''
+  "download.${config.const.host.domain}".extraConfig = ''
     listen 443 ssl;
 
     location / {
diff --git a/option/Const.nix b/option/Const.nix
new file mode 100644
index 0000000..78e94f1
--- /dev/null
+++ b/option/Const.nix
@@ -0,0 +1,26 @@
+{ lib, ... }:
+{
+  options.const = {
+    droidStateVersion = lib.mkOption {
+      default = "24.05";
+      type = lib.types.str;
+    };
+    stateVersion = lib.mkOption {
+      default = "24.11";
+      type = lib.types.str;
+    };
+    timeZone = lib.mkOption {
+      default = "Europe/Moscow";
+      type = lib.types.str;
+    };
+    url = lib.mkOption {
+      default = "https://git.voronind.com/voronind/nix.git";
+      type = lib.types.str;
+    };
+    host = lib.mkOption {
+      default = { };
+      type = lib.types.attrs;
+    };
+  };
+}
+
diff --git a/system/Locale.nix b/system/Locale.nix
index 483949d..259afad 100644
--- a/system/Locale.nix
+++ b/system/Locale.nix
@@ -1,6 +1,6 @@
-{ const, ... }:
+{ config, ... }:
 {
-  time.timeZone = const.timeZone;
+  time.timeZone = config.const.timeZone;
   i18n = {
     defaultLocale = "en_US.UTF-8";
     extraLocaleSettings = {
diff --git a/system/State.nix b/system/State.nix
new file mode 100644
index 0000000..cb47642
--- /dev/null
+++ b/system/State.nix
@@ -0,0 +1,5 @@
+{ config, ... }: {
+  # Specify current release version.
+  system.stateVersion = config.const.stateVersion;
+}
+