enable host key generation on first boot

base.nix

@@ -120,10 +120,6 @@ with lib;
         root:x:0:
         nixbld:x:30000:nixbld1,nixbld10,nixbld2,nixbld3,nixbld4,nixbld5,nixbld6,nixbld7,nixbld8,nixbld9
       '';
-      "ssh/ssh_host_rsa_key.pub".source = ./ssh/ssh_host_rsa_key.pub;
-      "ssh/ssh_host_rsa_key" = { mode = "0600"; source = ./ssh/ssh_host_rsa_key; };
-      "ssh/ssh_host_ed25519_key.pub".source = ./ssh/ssh_host_ed25519_key.pub;
-      "ssh/ssh_host_ed25519_key" = { mode = "0600"; source = ./ssh/ssh_host_ed25519_key; };
     };
     boot.kernelParams = [ "systemConfig=${config.system.build.toplevel}" ];
     boot.kernelPackages = lib.mkDefault (if pkgs.system == "armv7l-linux" then pkgs.linuxPackages_rpi1 else pkgs.linuxPackages);

runit.nix

@@ -2,7 +2,6 @@
 
 let
   sshd_config = pkgs.writeText "sshd_config" ''
-    HostKey /etc/ssh/ssh_host_rsa_key
     HostKey /etc/ssh/ssh_host_ed25519_key
     Port 22
     PidFile /run/sshd.pid
@@ -30,6 +29,13 @@ in
     {
       "runit/1".source = pkgs.writeScript "1" ''
         #!${pkgs.runtimeShell}
+
+        ED25519_KEY="/etc/ssh/ssh_host_ed25519_key"
+
+        if [ ! -f $ED25519_KEY ]; then
+          ${pkgs.openssh}/bin/ssh-keygen -t ed25519 -f $ED25519_KEY -N ""
+        fi
+
         ${lib.optionalString config.not-os.simpleStaticIp ''
         ip addr add 10.0.2.15 dev eth0
         ip link set eth0 up