diff --git a/config/files/builders b/config/files/builders
index 6e1fdd7..efcd1ac 100644
--- a/config/files/builders
+++ b/config/files/builders
@@ -1 +1 @@
-ssh://nixremote@seras.kyouma.net x86_64-linux,aarch64-linux - 40 5 nixos-test,benchmark,big-parallel,kvm
+ssh://build@seras.kyouma.net x86_64-linux,aarch64-linux - 40 5 nixos-test,benchmark,big-parallel,kvm
diff --git a/config/hosts/seras/configuration.nix b/config/hosts/seras/configuration.nix
index 28d7699..351f0f8 100644
--- a/config/hosts/seras/configuration.nix
+++ b/config/hosts/seras/configuration.nix
@@ -14,7 +14,14 @@
     hostName = "seras";
     nftables.enable = lib.mkForce false;
   };
-  nix.settings.trusted-users = [ "nixremote" ];
+  nix.gc.options = lib.mkForce "--delete-older-than 60d";
+  nix.settings.trusted-users = [ "build" ];
+  nix.extraOptions = ''
+    min-free = ${builtins.toString (4096 * 1024 * 1024)}
+    max-free = ${builtins.toString (8192 * 1024 * 1024)}
+    max-substitution-jobs = 20
+    max-silent-time = 900
+  '';
   nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
 
   systemd.network.networks."98-eth-default" = {
@@ -22,7 +29,7 @@
       "2a0f:be01:0:100::169/128" 
     ];
   };
-  users.users.nixremote = {
+  users.users.build = {
     isNormalUser = true;
     shell = pkgs.fish;
     ignoreShellProgramCheck = true;
diff --git a/config/profiles/headless.nix b/config/profiles/headless.nix
index dd64f1c..1fe23d4 100644
--- a/config/profiles/headless.nix
+++ b/config/profiles/headless.nix
@@ -1,6 +1,12 @@
-{ config, lib, ... }: with lib; {
+{ config, lib, pkgs, ... }: {
+
   kyouma.machine-type.headless = true;
+
   documentation.man.generateCaches = false;
-  services.openssh.enable = mkDefault true;
-  services.vnstat.enable = mkDefault true;
+  environment.systemPackages = with pkgs; [
+    vim
+  ];
+
+  services.openssh.enable = lib.mkDefault true;
+  services.vnstat.enable = lib.mkDefault true;
 }
diff --git a/config/profiles/remote-build.nix b/config/profiles/remote-build.nix
index 1b8e134..2c49322 100644
--- a/config/profiles/remote-build.nix
+++ b/config/profiles/remote-build.nix
@@ -1,11 +1,16 @@
 {config, lib, pkgs, ... }: {
   nix.buildMachines = [{
     hostName = "seras.kyouma.net";
-    sshUser = "nixremote";
+    sshUser = "build";
     maxJobs = 40;
     speedFactor = 5;
     systems = [ "aarch64-linux" "x86_64-linux" ];
     supportedFeatures = [ "nixos-test" "benchmark" "big-parallel" "kvm" ];
   }];
   nix.distributedBuilds = true;
+  programs.ssh = {
+    knownHosts = {
+      "seras.kyouma.net".publicKey = "sh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPNVavo3YHVsrYwXRVISu7kDoknn+5inFGySn4azlB8P";
+    };
+  };
 }
diff --git a/flake.nix b/flake.nix
index 0cc822d..1b61b9e 100644
--- a/flake.nix
+++ b/flake.nix
@@ -43,9 +43,9 @@
     };
   };
 
-  nixConfig = rec {
+  nixConfig = {
     builders-use-substitutes = true;
-    builders = "ssh://nixremote@seras.kyouma.net x86_64-linux,aarch64-linux - 40 5 nixos-test,benchmark,big-parallel,kvm";
+    builders = "ssh://build@seras.kyouma.net x86_64-linux,aarch64-linux - 40 5 nixos-test,benchmark,big-parallel,kvm";
   };
 
   outputs = { self, nixpkgs, flake-utils, ... }@inputs: {