#8 Problem compile on debian etch

[Perugini Alessandro]

i have a problem compiling it on debian etch:
when i call make i get the error /lib/modules/2.6.18-4-686/build not such
file or directory

i create the directory build (/lib/modules/2.6.18-4-686 exists) and now if
i call make as root i receive the following error:

pServer:~/ibcs# make
make -C /lib/modules/2.6.18-4-686/build M=/root/ibcs modules
make[1]: Entering directory `/lib/modules/2.6.18-4-686/build'
make[1]: *** No rule to make target `modules'. Stop.
make[1]: Leaving directory `/lib/modules/2.6.18-4-686/build'
make: *** [all] Error 2

someone can help me to understand this error?