nixos: introduce system.nixosLabel option and use it where appropriate

Setting nixosVersion to something custom is useful for meaningful GRUB
menus and /nix/store paths, but actuallly changing it rebulids the
whole system path (because of `nixos-version` script and manual
pages). Also, changing it is not a particularly good idea because you
can then be differentitated from other NixOS users by a lot of
programs that read /etc/os-release.

This patch introduces an alternative option that does all you want
from nixosVersion, but rebuilds only the very top system level and
/etc while using your label in the names of system /nix/store paths,
GRUB and other boot loaders' menus, getty greetings and so on.

2 files changed, 2 insertions, 2 deletions

diff --git a/nixos/modules/installer/cd-dvd/installation-cd-base.nix b/nixos/modules/installer/cd-dvd/installation-cd-base.nix
index bc3bd872d2a5f..2569860a098ff 100644
--- a/nixos/modules/installer/cd-dvd/installation-cd-base.nix
+++ b/nixos/modules/installer/cd-dvd/installation-cd-base.nix
@@ -16,7 +16,7 @@ with lib;
     ];
 
   # ISO naming.
-  isoImage.isoName = "${config.isoImage.isoBaseName}-${config.system.nixosVersion}-${pkgs.stdenv.system}.iso";
+  isoImage.isoName = "${config.isoImage.isoBaseName}-${config.system.nixosLabel}-${pkgs.stdenv.system}.iso";
 
   isoImage.volumeID = substring 0 11 "NIXOS_ISO";
 
diff --git a/nixos/modules/installer/cd-dvd/iso-image.nix b/nixos/modules/installer/cd-dvd/iso-image.nix
index fa9cc6fa20b98..b79191e0fd4ba 100644
--- a/nixos/modules/installer/cd-dvd/iso-image.nix
+++ b/nixos/modules/installer/cd-dvd/iso-image.nix
@@ -39,7 +39,7 @@ let
     DEFAULT boot
 
     LABEL boot
-    MENU LABEL NixOS ${config.system.nixosVersion}${config.isoImage.appendToMenuLabel}
+    MENU LABEL NixOS ${config.system.nixosLabel}${config.isoImage.appendToMenuLabel}
     LINUX /boot/bzImage
     APPEND init=${config.system.build.toplevel}/init ${toString config.boot.kernelParams}
     INITRD /boot/initrd