cygwin在windows8下 600 变660 解决方案

重装系统，把老的sshkey拷回来，发现权限不对，于是chmod 600之，发现权限并没有如期变成600而是变成了660，据说这是cygwin在windows下的bug

解决方法如下，先修属组，在修改权限 

chgrp -Rv Users ~/.ssh/id_rsa 
chmod -vR 600 ~/.ssh/id_rsa

摘自

http://superuser.com/questions/397288/using-cygwin-in-windows-8-chmod-600-does-not-work-as-expected

http://stackoverflow.com/questions/1556119/ssh-private-key-permissions-using-git-gui-or-ssh-keygen-are-too-open