Compiling and Installing the Custom Kernel
After your config file is ready to go, building the kernel is a fairly simple process. In theory, it's at most three commands:
# cd /usr/src # make buildkernel KERNCONF=CUSTOM # make installkernel KERNCONF=CUSTOM
The KERNCONF argument specifies the kernel config file to use; if you omit it, the GENERIC config file will be assumed. The first step parses the config file, sets up the build directory, builds the dependencies, and then builds the kernel itself. The second line installs it into /boot, moving the current kernel to /boot/kernel.old. You must then reboot to use the new kernel.
If you're really sure of yourself, you can combine both the make lines into a single one:
# make kernel KERNCONF=CUSTOM ...