How to make world (for FreeBSD)

1. rm -r /usr/obj              <-- optional
2. make -j4 KERNCONF=MY_KERNEL buildworld <-- MY_KERNEL is Kernel Configlation File        
3. make -j4 KERNCONF=MY_KERNEL buildkernel
4. shutdown now                <-- down to single user mode
5. make KERNCONF=MY_KERNEL installworld 
6. make KERNCONF=MY_KERNEL installkernel 
7. mergemaster
8. cd /dev/ && sh ./MAKEDEV all
9. cd /usr/src/release/sysinstall && make all install
10. fastboot
11. enjoy!

mergemaster tips 
% mergemaster -siva (copy the file(s) not in current env.) 
  && mergemaster -sivr (apply changed file(s))