* An option nix.useChroot to enable chroot builds in NixOS.

svn path=/nixos/trunk/; revision=9583

etc/default.nix

@@ -116,6 +116,17 @@ import ../helpers/make-etc.nix {
       target = "inputrc";
     }
 
+    { # Nix configuration.
+      source = pkgs.writeText "nix.conf" "
+        # WARNING: this file is generated.
+        build-users-group = nixbld
+        build-max-jobs = ${toString (config.get ["nix" "maxJobs"])}
+        build-use-chroot = ${if config.get ["nix" "useChroot"] then "true" else "false"}
+        build-chroot-dirs = /dev /proc /bin /etc
+        ${config.get ["nix" "extraOptions"]}
+      ";
+      target = "nix.conf"; # will be symlinked from /nix/etc/nix/nix.conf in activate-configuration.sh.
+    }
   ]
 
   # Configuration file for fontconfig used to locate

system/activate-configuration.sh

@@ -101,17 +101,8 @@ fi
 
 # Set up Nix.
 if test -z "@readOnlyRoot@"; then
-
     mkdir -p /nix/etc/nix
-    cat > /nix/etc/nix/nix.conf <<EOF
+    ln -sfn /etc/nix.conf /nix/etc/nix/nix.conf
-# WARNING: this file is generated.
-build-users-group = nixbld
-build-max-jobs = @maxJobs@
-
-@extraNixOptions@
-
-EOF
-
     chown root.nixbld /nix/store
     chmod 1775 /nix/store
 fi

system/options.nix

@@ -1073,15 +1073,27 @@
     ";
   }
 
+  {
+    name = ["nix" "useChroot"];
+    default = false;
+    example = true;
+    description = "
+      If set, Nix will perform builds in a chroot-environment that it
+      will set up automatically for each build.  This prevents
+      impurities in builds by disallowing access to dependencies
+      outside of the Nix store.
+    ";
+  }
+  
   {
     name = ["nix" "extraOptions"];
     default = "";
     example = "
-	gc-keep-outputs = true
+      gc-keep-outputs = true
-	gc-keep-derivations = true
+      gc-keep-derivations = true
     ";
     description = "
-	This option allows to append lines to nix.conf. 
+      This option allows to append lines to nix.conf. 
     ";
   }
   

system/system.nix

@@ -266,8 +266,6 @@ rec {
       config.get ["security" "setuidPrograms"] ++
       config.get ["security" "extraSetuidPrograms"] ++
       pkgs.lib.optional (config.get ["security" "sudo" "enable"]) "sudo";
-    maxJobs = config.get ["nix" "maxJobs"];
-    extraNixOptions = config.get ["nix" "extraOptions"];
 
     inherit (usersGroups) createUsersGroups usersList groupsList;