Get the Linux Kernel make process to rebuild modified files

Question

I'm building a custom Ubuntu kernel and have modified one of the source files. When I issue the build command:

NOEXTRAS=1 skipabi=true skipmodule=true fakeroot debian/rules binary-insp8600

it rebuilds the debs, but none of the modified source files are rebuilt.

What's up? Do I have to do a completely clean rebuild every time I modify a source file?

That doesn't make any sense.

The file modified was ./init/main.c.

As a note binary-insp8600 is a custom flavor I created for my Inspiron 8600 laptop.

Answer 1

You shouldn't have to do a clean build if the dependancies in the Makefile are correct.

Is the file you changed a header file? If it is then run makedepend to add the header file dependencies automatically :)

If it isn't a header file then their really should be a dependency in the Makefile if it is part of the compilation, have a search and make sure the target you are using depends on the module you want to compile

Answer 2

debian/rules is not the kernel Makefile. It has no way of knowing the file you edited is a dependency of the final kernel, since these dependencies are in the real Makefile.

In fact, I would expect the debian/rules build target (the one which actually does the compilation) to depend only on a "flag" file it creates after finishing the build. If that is the case, a simple workaround would be to remove that "flag" file; it would then compile everything again (by calling the kernel's Makefile, which would know how to do a partial rebuild. Of course, that's assuming the build target does not try to be tidy and do a make clean or equivalent...)

(I did not look at the debian/rules for the package you are using, so I might be wrong, but at least it is a start.)