This package uses CDBS (and therefore simple-patchsys.mk) in order to apply patches to the upstream source. Patches are stored in debian/patches and their filenames usually end in .patch or .diff . For further details, see the man page for cdbs-edit-patch. All commands described below should be run from the top directory of the package source tree, unless otherwise stated. * To generate the fully patched source, in a form ready for editing, that would be built to create Debian packages, run: make -f debian/rules apply-patches Note: It has been proposed that, in future, this should happen automatically when you run dpkg-source -x on a CDBS simple-patchsys.mk source package. However, this proposal has apparently not yet been implemented, so for now you have to do it yourself like this. * To modify the source and save those modifications so that they will be applied when building the package, pick a suitably informative patch file name, for example 01_add_README.source_file.patch, and then run: cdbs-edit-patch 01_add_README.source_file.patch This will place you in a new shell in a temporary copy of the source tree. Make your desired modifications to it, and then exit the shell to create the patch file containing them (this file will appear in debian/patches). * To remove source modifications that are currently being applied when building the package, run: make -f debian/rules reverse-patches