patch

A patch is a text file containing source code differences between a development tree and the original snapshot from which the developer started work

apply patch:

ex:  if x.y.z-mm2.bz2 is a patch, go to the directory of linux source

      bzip2  -dc  ../x.y.z-mm2.bz2 |  patch -p1

create patch:

ex:

diff  -Nur   /path/originalKernal/    /path/newKernel  >  change changes.patch