From 0c20feb231eb9a98bcf8b7ee3f2876302437e8ca Mon Sep 17 00:00:00 2001
From: Richard Marko <srk@48.io>
Date: Sat, 17 Feb 2018 23:33:24 +0100
Subject: [PATCH] use overlayfs by default for netboot and iso

---
 nixos/modules/installer/cd-dvd/iso-image.nix | 14 +++++++++-----
 nixos/modules/installer/netboot/netboot.nix  | 14 +++++++++-----
 nixos/modules/system/boot/stage-1-init.sh    | 13 ++++++++-----
 3 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/nixos/modules/installer/cd-dvd/iso-image.nix b/nixos/modules/installer/cd-dvd/iso-image.nix
index 11319e5f4f82..4558b4dc9552 100644
--- a/nixos/modules/installer/cd-dvd/iso-image.nix
+++ b/nixos/modules/installer/cd-dvd/iso-image.nix
@@ -569,14 +569,18 @@ in
       };
 
     fileSystems."/nix/store" =
-      { fsType = "unionfs-fuse";
-        device = "unionfs";
-        options = [ "allow_other" "cow" "nonempty" "chroot=/mnt-root" "max_files=32768" "hide_meta_files" "dirs=/nix/.rw-store=rw:/nix/.ro-store=ro" ];
+      { fsType = "overlay";
+        device = "overlay";
+        options = [
+          "lowerdir=/nix/.ro-store"
+          "upperdir=/nix/.rw-store/store"
+          "workdir=/nix/.rw-store/work"
+        ];
       };
 
-    boot.initrd.availableKernelModules = [ "squashfs" "iso9660" "uas" ];
+    boot.initrd.availableKernelModules = [ "squashfs" "iso9660" "uas" "overlay" ];
 
-    boot.initrd.kernelModules = [ "loop" ];
+    boot.initrd.kernelModules = [ "loop" "overlay" ];
 
     # Closures to be copied to the Nix store on the CD, namely the init
     # script and the top-level system configuration directory.
diff --git a/nixos/modules/installer/netboot/netboot.nix b/nixos/modules/installer/netboot/netboot.nix
index 5146858cccf5..95eba86bcb65 100644
--- a/nixos/modules/installer/netboot/netboot.nix
+++ b/nixos/modules/installer/netboot/netboot.nix
@@ -50,14 +50,18 @@ with lib;
       };
 
     fileSystems."/nix/store" =
-      { fsType = "unionfs-fuse";
-        device = "unionfs";
-        options = [ "allow_other" "cow" "nonempty" "chroot=/mnt-root" "max_files=32768" "hide_meta_files" "dirs=/nix/.rw-store=rw:/nix/.ro-store=ro" ];
+      { fsType = "overlay";
+        device = "overlay";
+        options = [
+          "lowerdir=/nix/.ro-store"
+          "upperdir=/nix/.rw-store/store"
+          "workdir=/nix/.rw-store/work"
+        ];
       };
 
-    boot.initrd.availableKernelModules = [ "squashfs" ];
+    boot.initrd.availableKernelModules = [ "squashfs" "overlay" ];
 
-    boot.initrd.kernelModules = [ "loop" ];
+    boot.initrd.kernelModules = [ "loop" "overlay" ];
 
     # Closures to be copied to the Nix store, namely the init
     # script and the top-level system configuration directory.
diff --git a/nixos/modules/system/boot/stage-1-init.sh b/nixos/modules/system/boot/stage-1-init.sh
index f520bf54ad1b..8736613c3d25 100644
--- a/nixos/modules/system/boot/stage-1-init.sh
+++ b/nixos/modules/system/boot/stage-1-init.sh
@@ -334,8 +334,10 @@ mountFS() {
 
     # Filter out x- options, which busybox doesn't do yet.
     local optionsFiltered="$(IFS=,; for i in $options; do if [ "${i:0:2}" != "x-" ]; then echo -n $i,; fi; done)"
+    # Prefix (lower|upper|work)dir with /mnt-root (overlayfs)
+    local optionsPrefixed="$( echo "$optionsFiltered" | sed -E 's#\<(lowerdir|upperdir|workdir)=#\1=/mnt-root#g' )"
 
-    echo "$device /mnt-root$mountPoint $fsType $optionsFiltered" >> /etc/fstab
+    echo "$device /mnt-root$mountPoint $fsType $optionsPrefixed" >> /etc/fstab
 
     checkFS "$device" "$fsType"
 
@@ -354,10 +356,11 @@ mountFS() {
             ;;
     esac
 
-    # Create backing directories for unionfs-fuse.
-    if [ "$fsType" = unionfs-fuse ]; then
-        for i in $(IFS=:; echo ${options##*,dirs=}); do
-            mkdir -m 0700 -p /mnt-root"${i%=*}"
+    # Create backing directories for overlayfs
+    if [ "$fsType" = overlay ]; then
+        for i in upper work; do
+             dir="$( echo "$optionsPrefixed" | grep -o "${i}dir=[^,]*" )"
+             mkdir -m 0700 -p "${dir##*=}"
         done
     fi