From deb4f88c2c2ec0eeb0c80fbf174d3e670ef5c8da Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Wed, 16 Dec 2009 18:57:02 +0000
Subject: [PATCH] * Let the GRUB menu builder detect whether /boot is on a
 different   partition from /.  If so, copy the kernels and initrds to /boot
 and   use paths relative to /boot in the GRUB configuration file.  This  
 makes the boot.loader.grub.bootDevice option obsolete.  (Is there a   way to
 mark obsolete options?)  It also makes it unnecessary to set  
 boot.loader.grub.copyKernels, although that option is still   available since
 it can speed up GRUB if the Nix store is very   large.

svn path=/nixos/trunk/; revision=18998
---
 doc/config-examples/root-on-lvm.nix         | 13 ++----
 modules/installer/grub/grub-menu-builder.sh | 48 ++++++++++++---------
 modules/installer/grub/grub.nix             | 15 +++----
 3 files changed, 35 insertions(+), 41 deletions(-)

diff --git a/doc/config-examples/root-on-lvm.nix b/doc/config-examples/root-on-lvm.nix
index 4fd4ca3a65c..2ea1e547921 100644
--- a/doc/config-examples/root-on-lvm.nix
+++ b/doc/config-examples/root-on-lvm.nix
@@ -1,9 +1,6 @@
 # This configuration has / on a LVM volume.  Since Grub
 # doesn't know about LVM, a separate /boot is therefore
-# needed.  In particular you need to set "copyKernels"
-# to tell NixOS to copy kernels and initrds from /nix/store
-# to /boot, and "bootMount" to tell Grub the /boot device
-# in Grub syntax (e.g. (hd0,0) for /dev/sda1).
+# needed.
 #
 # In this example, labels are used for file systems and
 # swap devices: "boot" might be /dev/sda1, "root" might be
@@ -12,12 +9,8 @@
 # that / is on LVM; that's figured out automatically.
 
 {
-  boot = {
-    grubDevice = "/dev/sda";
-    initrd.kernelModules = ["ata_piix"];
-    copyKernels = true;
-    bootMount = "(hd0,0)";
-  };
+  boot.loader.grub.device = "/dev/sda";
+  boot.initrd.kernelModules = ["ata_piix"];
 
   fileSystems = [
     { mountPoint = "/";
diff --git a/modules/installer/grub/grub-menu-builder.sh b/modules/installer/grub/grub-menu-builder.sh
index 1cce302fdf0..72ea17875c5 100644
--- a/modules/installer/grub/grub-menu-builder.sh
+++ b/modules/installer/grub/grub-menu-builder.sh
@@ -12,8 +12,6 @@ fi
 
 grubVersion="@version@"
 defaultConfig="$1"
-bootDevice="@bootDevice@"
-if test -z "$bootDevice"; then bootDevice=/boot; fi
 
 case "$grubVersion" in
     1|2)
@@ -27,6 +25,20 @@ case "$grubVersion" in
 esac
 
 
+# Discover whether /boot is on the same filesystem as /.  If not, then
+# all kernels and initrds must be copied to /boot, and all paths in
+# the GRUB config file must be relative to the root of the /boot
+# filesystem.  `$bootRoot' is the path to be prepended to paths under
+# /boot.
+if [ "$(stat -f -c '%i' /)" = "$(stat -f -c '%i' /boot)" ]; then
+    bootRoot=/boot
+    copyKernels="@copyKernels@" # user can override in the NixOS config
+else
+    bootRoot=
+    copyKernels=1
+fi
+
+
 prologue() {
     case "$grubVersion" in
 	1)
@@ -37,7 +49,7 @@ default @default@
 timeout @timeout@
 GRUBEND
 	    if test -n "@splashImage@"; then
-		echo "splashimage $bootDevice/background.xpm.gz" >> "$1"
+		echo "splashimage $bootRoot/background.xpm.gz" >> "$1"
 	    fi
 	    ;;
 	2)
@@ -46,7 +58,7 @@ GRUBEND
 # Automatically generated.  DO NOT EDIT THIS FILE!
 set default=@default@
 set timeout=@timeout@
-if loadfont $bootDevice/grub/unicode.pf2; then
+if loadfont $bootRoot/grub/unicode.pf2; then
   set gfxmode=640x480
   insmod gfxterm
   insmod vbe
@@ -59,7 +71,7 @@ EOF
 		# if it doesn't match the video resolution.
 		cat >> "$1" <<EOF
 insmod png
-if background_image $bootDevice/background.png; then
+if background_image $bootRoot/background.png; then
   set color_normal=white/black
   set color_highlight=black/white
 else
@@ -106,7 +118,8 @@ declare -A filesCopied
 
 copyToKernelsDir() {
     local src="$1"
-    local dst="/boot/kernels/$(cleanName $src)"
+    local p="kernels/$(cleanName $src)"
+    local dst="/boot/$p"
     # Don't copy the file if $dst already exists.  This means that we
     # have to create $dst atomically to prevent partially copied
     # kernels or initrd if this script is ever interrupted.
@@ -116,7 +129,7 @@ copyToKernelsDir() {
         mv $dstTmp $dst
     fi
     filesCopied[$dst]=1
-    result=$dst
+    result="$bootRoot/$p"
 }
 
 
@@ -147,34 +160,27 @@ addEntry() {
 	    1)
 		cat > /boot/nixos-grub-config <<EOF
 	title Emergency boot
-	kernel ${bootDevice:-/boot}/nixos-kernel systemConfig=$(readlink -f "$path") init=/boot/nixos-init $(cat "$path/kernel-params")
-	initrd ${bootDevice:-/boot}/nixos-initrd
+	kernel $bootRoot/nixos-kernel systemConfig=$(readlink -f "$path") init=/boot/nixos-init $(cat "$path/kernel-params")
+	initrd $bootRoot/nixos-initrd
 EOF
 		;;
 	    2)
 		cat > /boot/nixos-grub-config <<EOF
         menuentry "Emergency boot" {
-          linux  ${bootDevice:-/boot}/nixos-kernel systemConfig=$(readlink -f "$path") init=/boot/nixos-init $(cat "$path/kernel-params")
-          initrd ${bootDevice:-/boot}/initrd
+          linux  $bootRoot/nixos-kernel systemConfig=$(readlink -f "$path") init=/boot/nixos-init $(cat "$path/kernel-params")
+          initrd $bootRoot/initrd
         }
 EOF
 		;;
 	esac
     fi
 
-    if test -n "@copyKernels@"; then
+    if test -n "$copyKernels"; then
         copyToKernelsDir $kernel; kernel=$result
         copyToKernelsDir $initrd; initrd=$result
     fi
     
-    if test -n "$bootDevice"; then
-        kernel=$(echo $kernel | sed -e "s^/boot^$bootDevice^")
-        initrd=$(echo $initrd | sed -e "s^/boot^$bootDevice^")
-    fi
-    
-    local confName=$(if test -e $path/configuration-name; then 
-	cat $path/configuration-name; 
-    fi)
+    local confName=$(cat $path/configuration-name 2>/dev/null)
     if test -n "$confName"; then
 	name="$confName $3"
     fi
@@ -199,7 +205,7 @@ GRUBEND
 }
 
 
-if test -n "@copyKernels@"; then
+if test -n "$copyKernels"; then
     mkdir -p /boot/kernels
 fi
 
diff --git a/modules/installer/grub/grub.nix b/modules/installer/grub/grub.nix
index 0939abd6e18..e3df1593e71 100644
--- a/modules/installer/grub/grub.nix
+++ b/modules/installer/grub/grub.nix
@@ -13,7 +13,7 @@ let
     inherit (pkgs) bash;
     path = [pkgs.coreutils pkgs.gnused pkgs.gnugrep];
     inherit (config.boot.loader.grub) copyKernels extraEntries extraEntriesBeforeNixOS
-      splashImage bootDevice configurationLimit version default timeout;
+      splashImage configurationLimit version default timeout;
   };
   
 in
@@ -53,15 +53,10 @@ in
         '';
       };
 
+      # !!! How can we mark options as obsolete?
       bootDevice = mkOption {
         default = "";
-        example = "(hd0,0)";
-        description = ''
-          If the system partition may be wiped on reinstall, it is better
-          to have /boot on a small partition. To do it, we need to explain
-          to GRUB where the kernels live. Specify the partition here (in 
-          GRUB notation).
-        '';
+        description = "Obsolete.";
       };
 
       configurationName = mkOption {
@@ -121,8 +116,8 @@ in
         default = false;
         description = ''
           Whether the GRUB menu builder should copy kernels and initial
-          ramdisks to /boot.  This is necessary when /nix is on a
-          different file system than /boot.
+          ramdisks to /boot.  This is done automatically if /boot is
+          on a different partition than /.
         '';
       };