diff --git a/pkgs/build-support/build-fhs-chrootenv/default.nix b/pkgs/build-support/build-fhs-chrootenv/default.nix
index 41c60ea5fe8d..38bd3623d29e 100644
--- a/pkgs/build-support/build-fhs-chrootenv/default.nix
+++ b/pkgs/build-support/build-fhs-chrootenv/default.nix
@@ -14,11 +14,36 @@ assert targetPkgs != null -> multiPkgs  != null;
 assert multiPkgs  != null -> targetPkgs != null;
 assert targetPkgs != null -> pkgs       == [];
 
+
+# HOWTO:
+# If pkgs is defined buildFHSChrootEnv will run in legacy mode. This means
+# it will build all pkgs contained in pkgs and basePkgs and then just merge
+# all of their contents together via buildEnv.
+#
+# The new way is to define both targetPkgs and multiPkgs. These two are
+# functions which get a pkgs environment supplied and should then return a list
+# of packages based this environment.
+# For example: targetPkgs = pkgs: [ pkgs.nmap ];
+#
+# All packages (most likeley programs) placed in targetPkgs will only be
+# installed once--matching the hosts architecture (64bit on x86_64 and 32bit on
+# x86). These packages will populate the chroot directory tree.
+#
+# Packages (most likeley libraries) defined in multiPkgs will be installed once
+# on x86 systems and twice on x86_64 systems.
+# On x86 they will just be merge with the packages defined in targetPkgs.
+# On x86_64 they will be added to targetPkgs and in addition their 32bit
+# versions will also be installed. The final directory should look as follows:
+# /lib will include 32bit libraries from multiPkgs
+# /lib32 will link to /lib
+# /lib64 will include 64bit libraries from multiPkgs and targetPkgs
+# /x86 will contain a complete 32bit environment composed by multiPkgs
+
 let
   is64Bit       = system == "x86_64-linux";
   # enable multi builds on x86_64 hosts if pakgs_target/multi are defined
   isMultiBuild  = is64Bit && targetPkgs != null;
-  isNormalBuild = !isMultiBuild;
+  isTargetBuild = !isMultiBuild;
 
   # list of packages (usually programs) which will only be installed for the
   # hosts architecture
@@ -75,7 +100,7 @@ let
   destroySh = ./destroy.sh.in;
 
   linkProfile = profile: ''
-    for i in ${profile}/{etc,bin,lib{,32,64},sbin,share,var}; do
+    for i in ${profile}/{etc,bin,sbin,share,var}; do
         if [ -x "$i" ]
         then
             ln -s "$i"
@@ -86,9 +111,12 @@ let
   # the target profile is the actual profile that will be used for the chroot
   setupTargetProfile = ''
     ${linkProfile staticUsrProfileTarget}
+    ${setupLibDirs}
+
     mkdir -m0755 usr
     cd usr
     ${linkProfile staticUsrProfileTarget}
+    ${setupLibDirs}
     cd ..
   '';
 
@@ -97,21 +125,30 @@ let
   # /lib, /lib32 -> links to 32bit binaries
   # /lib64       -> links to 64bit binaries
   # /usr/lib*    -> same as above
-  setupMultiProfile = if isNormalBuild then "" else ''
+  setupMultiProfile = if isTargetBuild then "" else ''
     mkdir -m0755 x86
     cd x86
     ${linkProfile staticUsrProfileMulti}
     cd ..
-
-    ${setupMultiLibDirs}
-
-    cd usr
-    ${setupMultiLibDirs}
-    cd ..
   '';
 
-  setupMultiLibDirs = ''
-    rm -f lib lib32 lib64
+  setupLibDirs = if isTargetBuild then setupLibDirs_target
+                                  else setupLibDirs_multi;
+
+  # setup library paths only for the targeted architecture
+  setupLibDirs_target = ''
+    mkdir -m0755 lib
+
+    # copy content of targetPaths
+    cp -rsf ${staticUsrProfileTarget}/lib/* lib/
+
+    # copy gcc libs
+    cp -rsf ${choosenGcc.gcc}/lib/* lib/
+
+  '';
+
+  # setup /lib, /lib32 and /lib64
+  setupLibDirs_multi = ''
     mkdir -m0755 lib
     mkdir -m0755 lib64
     ln -s lib lib32
@@ -120,12 +157,13 @@ let
     cp -rsf ${staticUsrProfileTarget}/lib/32/* lib/
 
     # copy content of multiPaths (32bit libs)
-    cp -rsf ${staticUsrProfileMulti}/lib/*  lib/
+    cp -rsf ${staticUsrProfileMulti}/lib/* lib/
 
     # copy content of targetPaths (64bit libs)
-    cp -rsf ${staticUsrProfileTarget}/lib/*   lib64/
+    cp -rsf ${staticUsrProfileTarget}/lib/* lib64/
+
     # most 64bit only libs put their stuff into /lib
-    # some pkgs (like gcc_multi) put 32bit libs into /lib 64bit libs into /lib64
+    # some pkgs (like gcc_multi) put 32bit libs into and /lib 64bit libs into /lib64
     # by overwriting these we will hopefully catch all these cases
     # in the end /lib should only contain 32bit and /lib64 only 64bit libs
     cp -rsf ${staticUsrProfileTarget}/lib64/* lib64/