diff --git a/nixos/modules/installer/cd-dvd/sd-image-aarch64.nix b/nixos/modules/installer/cd-dvd/sd-image-aarch64.nix
index 517ddc75c87c..8cf349fbd078 100644
--- a/nixos/modules/installer/cd-dvd/sd-image-aarch64.nix
+++ b/nixos/modules/installer/cd-dvd/sd-image-aarch64.nix
@@ -1,3 +1,5 @@
+# To build, use:
+# nix-build nixos -I nixos-config=nixos/modules/installer/cd-dvd/sd-image-aarch64.nix -A config.system.build.sdImage
 { config, lib, pkgs, ... }:
 
 let
diff --git a/nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix b/nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix
index ded8af0a6ce2..76f5d4bf6472 100644
--- a/nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix
+++ b/nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix
@@ -1,3 +1,5 @@
+# To build, use:
+# nix-build nixos -I nixos-config=nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix -A config.system.build.sdImage
 { config, lib, pkgs, ... }:
 
 let
diff --git a/nixos/modules/installer/cd-dvd/sd-image-raspberrypi.nix b/nixos/modules/installer/cd-dvd/sd-image-raspberrypi.nix
index e7163f10a3c3..c7915b578d8a 100644
--- a/nixos/modules/installer/cd-dvd/sd-image-raspberrypi.nix
+++ b/nixos/modules/installer/cd-dvd/sd-image-raspberrypi.nix
@@ -1,3 +1,5 @@
+# To build, use:
+# nix-build nixos -I nixos-config=nixos/modules/installer/cd-dvd/sd-image-raspberrypi.nix -A config.system.build.sdImage
 { config, lib, pkgs, ... }:
 
 let