[cygwin]Howto make a portable cygwin environment

I, have thoroughly emigrated to Linux, need a Linux-Like environment
to make things better in my PC-Architecture course, so I decide to
make a portable cygwin environment.

Because I have no portable devices, such as Flash Disk. I have to
upload the whole environment to internet for further downloading.

Here is WHAT I do to make such a portable cygwin environment.

1. cp the cygwin which is already installed when I used windows to a
work directory named $cygwin.
2. write a script to make a cygwin environment, such as where is the
/, /usr and /bin in windows
use $cygwin/bin/mount to make mount points on which the
$cygwin/bin/bash depends to make a work environment.

/etc/profile will be read when evoke bash with a --login parameter,
namely evoke a login bash shell