Merge commit 'b3c692172e5b5241b028a98e1977f9fb12eeaf42'

2 files changed, 55 insertions, 44 deletions

diff --git a/nixpkgs/nixos/modules/installer/cd-dvd/installation-cd-base.nix b/nixpkgs/nixos/modules/installer/cd-dvd/installation-cd-base.nix
index aecb65b8c576..618057618d0c 100644
--- a/nixpkgs/nixos/modules/installer/cd-dvd/installation-cd-base.nix
+++ b/nixpkgs/nixos/modules/installer/cd-dvd/installation-cd-base.nix
@@ -30,6 +30,11 @@ with lib;
   # Add Memtest86+ to the CD.
   boot.loader.grub.memtest86.enable = true;
 
+  # An installation media cannot tolerate a host config defined file
+  # system layout on a fresh machine, before it has been formatted.
+  swapDevices = mkImageMediaOverride [ ];
+  fileSystems = mkImageMediaOverride config.lib.isoFileSystems;
+
   boot.postBootCommands = ''
     for o in $(</proc/cmdline); do
       case "$o" in
diff --git a/nixpkgs/nixos/modules/installer/cd-dvd/iso-image.nix b/nixpkgs/nixos/modules/installer/cd-dvd/iso-image.nix
index d94af0b5bf74..78cbf14bbaf6 100644
--- a/nixpkgs/nixos/modules/installer/cd-dvd/iso-image.nix
+++ b/nixpkgs/nixos/modules/installer/cd-dvd/iso-image.nix
@@ -615,53 +615,19 @@ in
 
   };
 
-  config = {
-    assertions = [
+  # store them in lib so we can mkImageMediaOverride the
+  # entire file system layout in installation media (only)
+  config.lib.isoFileSystems = {
+    "/" = mkImageMediaOverride
       {
-        assertion = !(stringLength config.isoImage.volumeID > 32);
-        # https://wiki.osdev.org/ISO_9660#The_Primary_Volume_Descriptor
-        # Volume Identifier can only be 32 bytes
-        message = let
-          length = stringLength config.isoImage.volumeID;
-          howmany = toString length;
-          toomany = toString (length - 32);
-        in
-        "isoImage.volumeID ${config.isoImage.volumeID} is ${howmany} characters. That is ${toomany} characters longer than the limit of 32.";
-      }
-    ];
-
-    boot.loader.grub.version = 2;
-
-    # Don't build the GRUB menu builder script, since we don't need it
-    # here and it causes a cyclic dependency.
-    boot.loader.grub.enable = false;
-
-    environment.systemPackages =  [ grubPkgs.grub2 grubPkgs.grub2_efi ]
-      ++ optional canx86BiosBoot pkgs.syslinux
-    ;
-
-    # In stage 1 of the boot, mount the CD as the root FS by label so
-    # that we don't need to know its device.  We pass the label of the
-    # root filesystem on the kernel command line, rather than in
-    # `fileSystems' below.  This allows CD-to-USB converters such as
-    # UNetbootin to rewrite the kernel command line to pass the label or
-    # UUID of the USB stick.  It would be nicer to write
-    # `root=/dev/disk/by-label/...' here, but UNetbootin doesn't
-    # recognise that.
-    boot.kernelParams =
-      [ "root=LABEL=${config.isoImage.volumeID}"
-        "boot.shell_on_fail"
-      ];
-
-    fileSystems."/" =
-      { fsType = "tmpfs";
+        fsType = "tmpfs";
         options = [ "mode=0755" ];
       };
 
     # Note that /dev/root is a symlink to the actual root device
     # specified on the kernel command line, created in the stage 1
     # init script.
-    fileSystems."/iso" =
+    "/iso" = mkImageMediaOverride
       { device = "/dev/root";
         neededForBoot = true;
         noCheck = true;
@@ -669,20 +635,20 @@ in
 
     # In stage 1, mount a tmpfs on top of /nix/store (the squashfs
     # image) to make this a live CD.
-    fileSystems."/nix/.ro-store" =
+    "/nix/.ro-store" = mkImageMediaOverride
       { fsType = "squashfs";
         device = "/iso/nix-store.squashfs";
         options = [ "loop" ];
         neededForBoot = true;
       };
 
-    fileSystems."/nix/.rw-store" =
+    "/nix/.rw-store" = mkImageMediaOverride
       { fsType = "tmpfs";
         options = [ "mode=0755" ];
         neededForBoot = true;
       };
 
-    fileSystems."/nix/store" =
+    "/nix/store" = mkImageMediaOverride
       { fsType = "overlay";
         device = "overlay";
         options = [
@@ -690,13 +656,53 @@ in
           "upperdir=/nix/.rw-store/store"
           "workdir=/nix/.rw-store/work"
         ];
-
         depends = [
           "/nix/.ro-store"
           "/nix/.rw-store/store"
           "/nix/.rw-store/work"
         ];
       };
+  };
+
+  config = {
+    assertions = [
+      {
+        assertion = !(stringLength config.isoImage.volumeID > 32);
+        # https://wiki.osdev.org/ISO_9660#The_Primary_Volume_Descriptor
+        # Volume Identifier can only be 32 bytes
+        message = let
+          length = stringLength config.isoImage.volumeID;
+          howmany = toString length;
+          toomany = toString (length - 32);
+        in
+        "isoImage.volumeID ${config.isoImage.volumeID} is ${howmany} characters. That is ${toomany} characters longer than the limit of 32.";
+      }
+    ];
+
+    boot.loader.grub.version = 2;
+
+    # Don't build the GRUB menu builder script, since we don't need it
+    # here and it causes a cyclic dependency.
+    boot.loader.grub.enable = false;
+
+    environment.systemPackages =  [ grubPkgs.grub2 grubPkgs.grub2_efi ]
+      ++ optional canx86BiosBoot pkgs.syslinux
+    ;
+
+    # In stage 1 of the boot, mount the CD as the root FS by label so
+    # that we don't need to know its device.  We pass the label of the
+    # root filesystem on the kernel command line, rather than in
+    # `fileSystems' below.  This allows CD-to-USB converters such as
+    # UNetbootin to rewrite the kernel command line to pass the label or
+    # UUID of the USB stick.  It would be nicer to write
+    # `root=/dev/disk/by-label/...' here, but UNetbootin doesn't
+    # recognise that.
+    boot.kernelParams =
+      [ "root=LABEL=${config.isoImage.volumeID}"
+        "boot.shell_on_fail"
+      ];
+
+    fileSystems = config.lib.isoFileSystems;
 
     boot.initrd.availableKernelModules = [ "squashfs" "iso9660" "uas" "overlay" ];