nixos/boot: some documentation improvements

- Give a more accurate description of how fileSystems.<name/>.neededForBoot
  works

- Give a more detailed description of how fileSystems.<name/>.encrypted.keyFile
  works

1 files changed, 6 insertions, 4 deletions

diff --git a/nixos/modules/system/boot/stage-1.nix b/nixos/modules/system/boot/stage-1.nix
index 63005b26f6f..7f13f67e8ef 100644
--- a/nixos/modules/system/boot/stage-1.nix
+++ b/nixos/modules/system/boot/stage-1.nix
@@ -559,10 +559,12 @@ in
           default = false;
           type = types.bool;
           description = ''
-            If set, this file system will be mounted in the initial
-            ramdisk.  By default, this applies to the root file system
-            and to the file system containing
-            <filename>/nix/store</filename>.
+            If set, this file system will be mounted in the initial ramdisk.
+            Note that the file system will always be mounted in the initial
+            ramdisk if its mount point is one of the following:
+            ${concatStringsSep ", " (
+              forEach utils.pathsNeededForBoot (i: "<filename>${i}</filename>")
+            )}.
           '';
         };
       });