cd /usr/src
make buildworld
make buildkernel KERNCONF=MyKernel_2
make installkernel KERNCONF=MyKernel_2
reboot

fsck -p
mount -u /
mount -a -t ufs
swapon -a
cd /usr/src
mergemaster -P
make installworld
make delete-old
mergemaster
reboot

make delete-old-libs