1. If you don’t know why you should patch/recompile kernel – DO NOT DO THIS.
2. If your running kernel is smart and supports all necessary hardware, technologies and doesn’t contain critical vulnerabilities – DO NOT REBUILD IT.
3. If you don’t know what are kernel patches and why they are used – DO NOT REBUILD KERNEL.
4. If kernel with needed functionality is available as binary package for your distribution (especially in official repositories) – DO NOT BUILD KERNEL.
5. If you insist, certainly read Kernel HOWTO and notes about kernel recompilation in regards to your distribution.
6. Do change kernel config values only if you know what they mean.
7. Don’t forget to build initrd before rebooting your system.
8. Do not remove workable kernel and make it default in boot loader menu (like grub).
9. Don’t panic if something goes wrong – most probably the same situation happened to thousands people earlier. But sometimes shit happens.
10. Rebuilding procedure usually takes hours depending on hardware you use. BE PATIENT!
11 (thanks to Erek Dyskant). Use your distro’s package management system to build kernels whenever possible (like make-kpkg in Debian or rpmbuild in Fedora/RedHat/CentOS)

I really hope this helps and pretty sure you’ll build your “perfect” kernel once

Any further advices are WELCOME!

P.S. Thanks to Stas Kogut for encouraging me to write this post.

viper@viper-laptop:~$ modinfo ati_agp
filename:       /lib/modules/2.6.20-16-lowlatency/kernel/drivers/char/agp/ati-agp.ko
license:        GPL and additional rights
author:         Dave Jones 
srcversion:     6920C657E39118CCE9BAC63
alias:          pci:v00001002d*sv*sd*bc06sc00i00*
depends:        agpgart
vermagic:       2.6.20-16-lowlatency SMP preempt mod_unload 586

First (kldload) would be useful for loading files *.ko into FreeBSD kernel using kernel linker. Second (kldstat) displays status of files loaded into kernel. Third (kldunload) helps to unload files which were previously loaded into kernel with kldload.

This utilities are analogues of modprobe and lsmod utilities in Linux.

Example: in order to enable ipfw kernel module without FreeBSD restarting you can do:

cd /boot/kernel
kldload ipfw.ko

Another way to enable ipfw is to add line firewall_enable="YES" into /etc/rc.conf and restart FreeBSD. But kldload method is much more easier and fast as for me

“Do you pine for the nice days of minix-1.1, when men were men and wrote their own device drivers?” began the October 5th, 1991 announcement for Linux kernel version 0.02 on the comp.os.minix newsgroup. In the release notes, Linus Torvalds continued, “as I mentioned a month ago, I’m working on a free version of a minix-lookalike for AT-386 computers. It has finally reached the stage where it’s even usable (though may not be depending on what you want), and I am willing to put out the sources for wider distribution.” 19 days after the 0.01 kernel was released, the 0.02 kernel debuted with the new-found ability to run a handful of utilities including bash, gcc, gnu-make, gnu-sed and compress. There was no floppy driver yet, the hard disk driver was hard coded to AT-compatible drives, and due to various buffer-cache problems it was not possible to compile large programs like gcc from a running 0.02 kernel.

Read more here.

One of the greatest features of the Linux® operating system is its networking stack. It was initially a derivative of the BSD stack and is well organized with a clean set of interfaces. Its interfaces range from the protocol agnostics, such as the common sockets layer interface or the device layer, to the specific interfaces of the individual networking protocols. This article explores the structure of the Linux networking stack from the perspective of its layers and also examines some of its major structures.

Anatomy of the Linux networking stack by IBM.