diff --git a/installer/default.nix b/installer/default.nix
index 46a1c941c8cb..6eb94bc3fc3c 100644
--- a/installer/default.nix
+++ b/installer/default.nix
@@ -7,6 +7,56 @@ let
     isExecutable = true;
   });
 
+  inherit (pkgs.lib) id all whatis escapeShellArg concatMapStrings concatMap
+  mapAttrs concatLists flattenAttrs filter;
+
+  # f adds svn defaults
+  # returns in any case:
+  # { type = git/svn; 
+  #   target = path;
+  #   initialize = cmd; # must create target dir, dirname target will exist
+  #   update = cmd;     # pwd will be target
+  #   default = true/false;
+  # }
+  f = repo : attrs :
+    assert (__isAttrs attrs);
+    assert (repo + "" == repo);
+    if (! (attrs ? type)) then 
+      throw "repo type is missing of : ${whatis attrs}"
+    else if attrs.type == "svn" then
+      let a = { # add svn defaults
+                url = "https://svn.nixos.org/repos/nix/${repo}/trunk";
+                target = "/etc/nixos/${repo}";
+              } // attrs; in
+      rec { 
+        inherit (a) type target;
+        default =  if a ? default then a.default else false;
+        initialize = "svn co ${a.url} ${a.target}"; 
+        update = initialize; # co is just as fine as svn update
+     }
+    else  if attrs.type == "git" then # sanity check for existing attrs
+      assert (all id (map ( attr : if __hasAttr attr attrs then true 
+                                     else throw "git repository item is missing attribute ${attr}")
+                          [ "target" "initialize" "update" ]
+                      ));
+    let t = escapeShellArg attrs.target; in
+    rec {
+      inherit (attrs) type target;
+      default =  if attrs ? default then attrs.default else false;
+      update = "cd ${t}; ${attrs.update}";
+      initialize =  ''
+    cd $(dirname ${t}); ${attrs.initialize}
+    [ -d ${t} ] || { echo "git initialize failed to create target directory ${t}"; exit 1; }
+    ${update}'';
+    }
+    else throw "unkown repo type ${attrs.type}"; in
+
+    # apply f on each repo definition
+    let repos = mapAttrs ( repo : list : map (x : (f repo x) // { inherit repo; } ) list ) config.installer.repos;
+
+    defaultRepo = list : __head ( (filter ( attrs : attrs ? default && attrs.default == true ) list)
+                                ++ list );
+
 in
 
 {
@@ -27,6 +77,8 @@ in
   };
 
   nixosRebuild = makeProg {
+    defaultNIXOS   = (defaultRepo repos.nixos  ).target;
+    defaultNIXPKGS = (defaultRepo repos.nixpkgs).target;
     name = "nixos-rebuild";
     src = ./nixos-rebuild.sh;
   };
@@ -36,9 +88,36 @@ in
     src = ./nixos-gen-seccure-keys.sh;
   };
 
-  nixosCheckout = makeProg {
+  nixosCheckout =
+    makeProg {
     name = "nixos-checkout";
-    src = ./nixos-checkout.sh;
+    src = pkgs.writeScript "nixos-checkout" (''
+          #! @shell@ -e
+          # this file is automatically generated from nixos configuration file settings (installer.repos)
+          backupTimestamp=$(date "+%Y%m%d%H%M%S")
+          '' + concatMapStrings ( attrs :
+                let repoType = __getAttr attrs.type config.installer.repoTypes; 
+                    target = escapeShellArg attrs.target; in
+                ''
+                  # ${attrs.type} repo ${target}
+                  PATH=
+                  for path in ${builtins.toString repoType.env}; do
+                    PATH=$PATH:$path/bin:$path/sbin
+                  done
+                  if [ -d  ${target} ] && { cd ${target} && { ${ repoType.valid}; }; }; then
+                      echo; echo '>>  ' updating ${attrs.type} repo ${target}
+                      set -x; ${attrs.update}; set +x
+                  else # [ make backup and ] initialize
+                      [ -e ${target} ] && mv ${target} ${target}-$backupTimestamp
+                      target=${target}
+                      [ -d "$(dirname ${target})" ] || mkdir -p  "$(dirname ${target})"
+                      echo; echo '>>  'initializing ${attrs.type} repo ${target}
+                      set -x; ${attrs.initialize}; set +x
+                  fi
+                ''
+              ) # flatten all repo definition to one list adding the repository
+               ( concatLists  (flattenAttrs repos) )
+      );
    };
 
   nixosHardwareScan = makeProg {
diff --git a/installer/nixos-checkout.sh b/installer/nixos-checkout.sh
deleted file mode 100644
index 0457f4d7cb7b..000000000000
--- a/installer/nixos-checkout.sh
+++ /dev/null
@@ -1,62 +0,0 @@
-#! @shell@ -e
-set -x
-
-# Pull the manifests defined in the configuration (the "manifests"
-# attribute).  Wonderfully hacky *and* cut&pasted from nixos-installer.sh!!!
-if test -z "$NIXOS"; then NIXOS=/etc/nixos/nixos; fi
-if test -z "$NIXOS_NO_PULL"; then
-    manifests=$(nix-instantiate --eval-only --xml --strict $NIXOS -A manifests \
-        | grep '<string'  | sed 's^.*"\(.*\)".*^\1^g')
-
-    mkdir -p /nix/var/nix/channel-cache
-    for i in $manifests; do
-        NIX_DOWNLOAD_CACHE=/nix/var/nix/channel-cache nix-pull $i || true
-    done
-fi
-
-# Obtain Subversion.
-if test -z "$(type -tp svn)"; then
-    #nix-channel --add http://nixos.org/releases/nixpkgs/channels/nixpkgs-unstable
-    #nix-channel --update
-    nix-env -i subversion
-fi
-
-cd /etc/nixos
-
-if test -n "$NIXOS" && test "$NIXOS_BRANCH" = 1 && test -z "$CHECKOUT_BRANCH" && ! test "$NIXOS" = "/etc/nixos/nixos"; then
-    CHECKOUT_BRANCH=${NIXOS##*/}
-    CHECKOUT_BRANCH=${CHECKOUT_BRANCH#nixos-}
-    CHECKOUT_BRANCH=branches/${CHECKOUT_BRANCH}
-    CHECKOUT_SUFFIX=-${CHECKOUT_BRANCH##*/}
-fi
-
-if test -n "${CHECKOUT_BRANCH}" && test -z "${CHECKOUT_SUFFIX}" ; then
-    CHECKOUT_SUFFIX=-${CHECKOUT_BRANCH##*/}
-fi;
-
-# Move any old nixos or nixpkgs directories out of the way.
-backupTimestamp=$(date "+%Y%m%d%H%M%S")
-
-if test -e nixos -a ! -e nixos/.svn; then
-    mv nixos${CHECKOUT_SUFFIX} nixos-$backupTimestamp
-fi
-
-if test -e nixpkgs -a ! -e nixpkgs/.svn; then
-    mv nixpkgs${CHECKOUT_SUFFIX} nixpkgs-$backupTimestamp
-fi
-
-if test -e services -a ! -e services/.svn; then
-    mv nixos/services services-$backupTimestamp
-fi
-
-# Check out the NixOS and Nixpkgs sources.
-svn co https://svn.nixos.org/repos/nix/nixos/trunk nixos${CHECKOUT_SUFFIX}
-svn co https://svn.nixos.org/repos/nix/nixpkgs/${CHECKOUT_BRANCH:-trunk} nixpkgs${CHECKOUT_SUFFIX}
-svn co https://svn.nixos.org/repos/nix/services/trunk services
-
-# Add a few required symlink.
-ln -sfn ../services nixos${CHECKOUT_SUFFIX}/services
-
-REVISION=$(svn info nixpkgs${CHECKOUT_SUFFIX} | egrep '^Revision: ');
-REVISION=${REVISION#Revision: };
-echo "\"$REVISION\"" > version.nix
diff --git a/installer/nixos-rebuild.sh b/installer/nixos-rebuild.sh
index 5ee1d29dd9c7..c173787d585a 100644
--- a/installer/nixos-rebuild.sh
+++ b/installer/nixos-rebuild.sh
@@ -42,8 +42,8 @@ fi
 
 # Allow the location of NixOS sources and the system configuration
 # file to be overridden.
-NIXOS=${NIXOS:-/etc/nixos/nixos}
-NIXPKGS=${NIXPKGS:-$NIXOS/pkgs}
+NIXOS=${NIXOS:-@defaultNIXOS@}
+NIXPKGS=${NIXPKGS:-@defaultNIXPKGS@}
 NIXOS_CONFIG=${NIXOS_CONFIG:-/etc/nixos/configuration.nix}
 
 
diff --git a/system/options.nix b/system/options.nix
index 8db9703c09bb..bea68e5283b5 100644
--- a/system/options.nix
+++ b/system/options.nix
@@ -2424,6 +2424,52 @@ in
       ";
     };
 
+    repos = {
+      nixos = mkOption {
+        default = [ { type  = "svn"; }  ];
+        example = [ { type = "svn"; url = "https://svn.nixos.org/repos/nix/nixos/branches/stdenv-updates"; target = "/etc/nixos/nixos-stdenv-updates"; }
+                    { type = "git"; initialize = ''git clone git://mawercer.de/nixos $target''; update = "git pull origin"; target = "/etc/nixos/nixos-git"; }
+                  ];
+        description = "The nixos repository from which the system will be build. 
+                       nixos-checkout will update all defined repositories,
+                       nixos-rebuild will use the the first item which has
+                       the attribute default = true falling back to the
+                       first item. the type defines the repository tool added
+                       to the path. It also defines a \"valid\" repository.
+                       If the target directory already exists and it's not
+                       valid it will be moved to the backup location
+                       <filename>\${dir}-date</filename>.
+                       For svn the default target and repositories are
+                       <filename>/etc/nixos/nixos</filename> and
+                       <filename>https://svn.nixos.org/repos/nix/nixos/trunk</filename>.
+                       For git repositories update is called after
+                       initialization when the repo is initialized.
+                       The initialize code is run from working directory
+                       dirname \$target and should create the directory
+                       <filename>\$target<filename>. (<command>git clone url nixos/nixpkgs/services</command> should do)
+                       ";
+      };
+
+      nixpkgs = mkOption {
+        default = [ { type  = "svn"; }  ];
+        description = "same as <option>repos.nixos</option>";
+      };
+
+      services = mkOption {
+        default = [ { type  = "svn"; } ];
+        description = "same as <option>repos.nixos</option>";
+      };
+    };
+
+    repoTypes = mkOption {
+        default = {
+          svn = { valid = "[ -d .svn ]"; env = [ pkgs.coreutils pkgs.subversion ]; };
+          git = { valid = "[ -d .git ]"; env = [ pkgs.coreutils pkgs.git pkgs.gnused /*  FIXME: use full path to sed in nix-pull */ ]; };
+        };
+        description = "defines PATH environment and when directory is considered beeing a valid repository.
+              If it's not it's moved to a backup directory";
+    };
+
     manifests = mkOption {
       default = [http://nixos.org/releases/nixpkgs/channels/nixpkgs-unstable/MANIFEST];
       example =