Let me guess: this is because the jar utility doesn't like Cygwin paths.?
(cd C:/Prg/jdk1.7.0/build-fastdebug/classes && C:/Prg/jdk1.6.0/bin/jar xf /cygd rive/c/Prg/OpenJDK/openjdk-binary-plugs/jre/lib/rt-closed.jar @C:/Prg/jdk1.7.0/b uild-fastdebug/tmp/java/plugs/jmf.clist -J-client -J-Xmx383m -J-Xms128m -J-XX:Pe rmSize=32m -J-XX:MaxPermSize=160m ) java.io.FileNotFoundException: \cygdrive\c\Prg\OpenJDK\openjdk-binary-plugs\jre\ lib\rt-closed.jar (The system cannot find the path specified) at java.io.FileInputStream.open(Native Method) at java.io.FileInputStream.<init>(FileInputStream.java:106) at java.io.FileInputStream.<init>(FileInputStream.java:66) at sun.tools.jar.Main.run(Main.java:205) at sun.tools.jar.Main.main(Main.java:1022) make[5]: *** [import-binary-plug-jmf-classes] Error 1 make[5]: Leaving directory `/cygdrive/c/Prg/OpenJDK/openjdk/jdk/make/java/redist ' make[4]: *** [all] Error 1 I would suggest, as an RFE or bug, that the various macros used on Windows have some kind of naming convention to them to indicate where a Cygwin path is needed, where an MS-style path is needed, and where it makes no difference. (But I have no offhand suggestions as to what that naming convention would look like, or how it might interact with the build macros for other platforms.) There's just GOT to be some kind of way to tell these apart, though. :-/ Ted Neward | Principal Consultant, ThoughtWorks Java, .NET, XML Services Consulting, Teaching, Speaking, Writing <http://www.tedneward.com> http://www.thoughtworks.com | <http://www.tedneward.com> http://www.tedneward.com