diff --git a/README.md b/README.md
index f06763d..bcb2ea3 100644
--- a/README.md
+++ b/README.md
@@ -31,11 +31,10 @@ Then ensure you have the following installed on your Linux/FreeBSD box:
 `Clang 3.2+`, `llvm-devel`, `automake`, `autogen`, `libtool`,  
 `libxml2-devel` (<=10.5 only), `uuid-devel`, `openssl-devel` and the `bash shell`.
 
-Hint: On Ubuntu 12.04 LTS you can use [llvm.org/apt](http://llvm.org/apt) to get a newer version of clang.
+Hint 1: You can run 'sudo tools/get_dependencies.sh' to get these automatically
+Hint 2: On Ubuntu 12.04 LTS you can use [llvm.org/apt](http://llvm.org/apt) to get a newer version of clang.
 
-Now edit the `SDK_VERSION` in `build.sh`, so it matches the version you have downloaded before.
-
-Then run `./build.sh` to build the cross toolchain (it will build in its own directory).
+Then run `./build.sh` to build the cross toolchain (it will search 'tarballs' for an SDK and then build in its own directory).
 
 **Don't forget** to add the printed `` `<path>/osxcross-env` `` to your `~/.profile` or `~/.bashrc`.  
 Then either run `source ~/.profile` or restart your shell session.
diff --git a/build.sh b/build.sh
index ac79a64..683fd0f 100755
--- a/build.sh
+++ b/build.sh
@@ -4,8 +4,58 @@ pushd "${0%/*}" &>/dev/null
 
 source tools/tools.sh
 
-# SDK version to use
-SDK_VERSION=10.8
+# find sdk version to use
+guess_sdk_version()
+{
+    tmp1=
+    tmp2=
+    tmp3=
+    file=
+    sdk=
+    sdkcount=`ls tarballs/ | grep MacOSX | wc -l`
+    sdks=`ls tarballs/ | grep MacOSX`
+    if [ $sdkcount -eq 0 ]; then
+        echo no SDK found in 'tarballs/'. please see README.md
+        exit
+    elif [ $sdkcount -gt 1 ]; then
+        for sdk in $sdks; do echo $sdk; done
+        echo 'more than one MacOSX SDK tarball found. please set'
+        echo 'SDK_VERSION environment variable for the one you want'
+        echo '(for example: run   SDK_VERSION=10.x build.sh   )'
+        exit 1
+    else
+        sdk=$sdks # only 1
+        tmp2=`echo $sdk | sed s/[^0-9.]//g`
+        tmp3=`echo $tmp2 | sed s/\\\.*$//g`
+        guess_sdk_version_result=$tmp3
+        echo 'found SDK version' $SDK_VERSION 'at tarballs/'$sdk
+    fi
+    export guess_sdk_version_result
+}
+
+# make sure there is actually a file with the given SDK_VERSION
+verify_sdk_version()
+{
+    sdkv=$1
+    for file in tarballs/*; do
+        if [ `echo $file | grep OSX.*$sdkv` ]; then
+            echo "verified at tarballs/"$file
+            sdk=$file
+        fi
+    done
+    if [ ! $sdk ] ; then
+        echo cant find SDK for OSX $sdkv in tarballs. exiting
+        exit
+    fi
+}
+
+if [ $SDK_VERSION ]; then
+    echo 'SDK VERSION set in environment variable: ' $SDK_VERSION
+else
+    guess_sdk_version
+    SDK_VERSION=$guess_sdk_version_result
+fi
+verify_sdk_version $SDK_VERSION
 
 # Minimum targeted OS X version
 # Must be <= SDK_VERSION
diff --git a/tools/trap_exit.sh b/tools/trap_exit.sh
index 63ba829..b56fa26 100644
--- a/tools/trap_exit.sh
+++ b/tools/trap_exit.sh
@@ -1,5 +1,15 @@
 #!/usr/bin/env bash
 
+function check_for_bug_1242300()
+{
+    if [ -e /etc/issue ]; then
+        if [ "`grep -i ubuntu.13.10 /etc/issue`" ]; then
+            echo "Ubuntu 13.10 detected. if there was a 'configure:' error"
+            echo "please see https://bugs.launchpad.net/ubuntu/+source/llvm-defaults/+bug/1242300"
+        fi
+    fi
+}
+
 function _exit()
 {
     EC=$?
@@ -12,6 +22,7 @@ function _exit()
         remove_locks
         echo "if it is happening the first time, then just re-run the script"
         echo ""
+        check_for_bug_1242300
     fi
 }