Ever since my college days, I always loved to have my own
compiled
kernel. It gave me that special feeling of “my machine is better
than
yours”. I am sure each time my new kernel boots up the feeling I
have
is is the same as what Super Man has when he bashs up the bad
people.
A custom kernel boots up the system faster, it takes up lesser
memory space and one can install drivers for hardware not
supported by a default kernel. Besides these benefits, a custom
kernel
serves as an interesting conversation topic with geeks. Just ask
them
“What is your kernel size ?”. This would keep the Geek busy for
sometime where he would explain all the great things he did to
the
kernel options to optimize his box.
If you happen to be a geek yourself, this is a great question to
put forward to those lowly Nubies. They’ll never trouble you
with stories of their nephew or kid sister after this 
Before we get down to compiling our own kernel, it is a
wonderful idea
to backup the present kernel.
# cd /boot
# cp -pvr kernel kernel.orig
The original generic kernel is now stored as kernel.orig. In
case the
kernel does not boot (which has happened with me many times)
boot up
with the generic kernel and try again. Booting any other kernel
is
simple. At the boot time goto to the boot prompt and simple say
“boot
kernel.orig” and the default kernel would boot up.
The kernel sources are located in the /usr/src/sys directory. If
not
installed, the kernel sources can be installed with the
following
commands. First insert the FreeBSD install CD in your CD drive.
# mount /cdrom# mkdir -p /usr/src/sys# ln -s /usr/src/sys /sys# cat /cdrom/src/ssys.[a-d]* | tar -xzvf -
Then go to the director where the configuration files are
located.
#cd /sys/i386/conf
In this directory the GENERIC kernel configuration file is
located.
Copy this file and it as your custom name.
#cp -pvr GENERIC BABYBSD
# vi BABYBSD
First change the ident value from GENERIC to BABYBSD (or
whatever name
you prefer). I have given my sample configuration file at the
end of
this article. The options are quite easy to understand and a
good
starting point would be the FreeBSD
Handbook which has documented most of the kernel options.
You can also go to a shell and run the command #make LINT
in
this directory which would create a file called LINT which has
all the
options supported by the kernel listed.
After this stage just run the following commands
#/usr/sbin/config BABYBSD
#cd ../compile/BABYBSD
#make depend
#make
#make install
Please note that you must be root to run the make install.
Reboot and
the kernel should boot with your shining new kernel. 
# My Sample Kernel Configuration File for FreeBSD/i386
machine i386
cpu
I586_CPU
cpu
I686_CPU
ident
BABYBSD
options SCHED_4BSD
# 4BSD scheduler
options INET
# InterNETworking
options INET6
# IPv6 communications protocols
options FFS
# Berkeley Fast Filesystem
options SOFTUPDATES
# Enable FFS soft updates support
options UFS_ACL
# Support for access control lists
options UFS_DIRHASH
# Improve performance on big directories
options MD_ROOT
# MD is a potential root device
options NFSCLIENT
# Network Filesystem Client
options NFSSERVER
# Network Filesystem Server
options NFS_ROOT
# NFS usable as /, requires NFSCLIENT
options MSDOSFS
# MSDOS Filesystem
options NTFS
options CD9660
# ISO 9660 Filesystem
options PROCFS
# Process filesystem (requires PSEUDOFS)
options PSEUDOFS
# Pseudo-filesystem framework
options GEOM_GPT
# GUID Partition Tables.
options COMPAT_43
# Compatible with BSD 4.3 [KEEP THIS!]
options COMPAT_FREEBSD4
# Compatible with FreeBSD4
options SCSI_DELAY=15000 #
Delay
(in ms) before probing SCSI
options KTRACE
# ktrace(1) support
options SYSVSHM
# SYSV-style shared memory
options SYSVMSG
# SYSV-style message queues
options SYSVSEM
# SYSV-style semaphores
options _KPOSIX_PRIORITY_SCHEDULING # POSIX
P1003_1B
real-time extensions
options KBD_INSTALL_CDEV #
install
a CDEV entry in /dev
options
AHC_REG_PRETTY_PRINT #
Print register bitfields in debug
# output. Adds ~128k
to
driver.
options
AHD_REG_PRETTY_PRINT #
Print register bitfields in debug
# output. Adds ~215k
to
driver.
options ADAPTIVE_GIANT
# Giant mutex is adaptive.
device
apic
# I/O APIC
# Bus support. Do not remove isa, even if you have no isa
slots
device isa
device eisa
device pci
# Floppy drives
device fdc
# ATA and ATAPI devices
device ata
device
atadisk
# ATA disk drives
device
atapicd
# ATAPI CDROM drives
options ATA_STATIC_ID #
Static
device numbering
# SCSI peripherals
device
scbus
# SCSI bus (required for SCSI)
device ch
# SCSI media changers
device da
# Direct Access (disks)
device cd
# CD
device
pass
# Passthrough device (direct SCSI access)
device
ses
# SCSI Environmental Services (and
SAF-TE)
# atkbdc0 controls both the keyboard and the PS/2 mouse
device
atkbdc
# AT keyboard controller
device
atkbd
# AT keyboard
device
psm
# PS/2 mouse
device
vga
# VGA video card driver
device
splash
# Splash screen and screen saver support
# syscons is the default console driver, resembling an SCO
console
device sc
# Enable this for the pcvt (VT220 compatible) console driver
#device vt
#options XSERVER
# support for X server on a vt console
#options FAT_CURSOR # start
with
block cursor
device
agp
# support several AGP chipsets
# Floating point support - do not disable.
device npx
# Power management support (see NOTES for more options)
#device apm
# Add suspend/resume support for the i8254.
device pmtimer
# PCI Ethernet NICs that use the common MII bus controller
code.
# NOTE: Be sure to keep the ‘device miibus’ line in order to use
these
NICs!
device
miibus
# MII bus support
device rl
# RealTek 8129/8139
# Wireless NIC cards
device
wlan
# 802.11 support
# Pseudo devices.
device
loop
# Network loopback
device
mem
# Memory and kernel memory devices
device io
# I/O device
device
random
# Entropy device
device
ether
# Ethernet support
device sl
# Kernel SLIP
device
ppp
# Kernel PPP
device
tun
# Packet tunnel.
device
pty
# Pseudo-ttys (telnet etc)
device md
# Memory “disks”
device
gif
# IPv6 and IPv4 tunneling
device
faith
# IPv6-to-IPv4 relaying (translation)
# The `bpf’ device enables the Berkeley Packet Filter.
# Be aware of the administrative consequences of enabling
this!
# Note that ‘bpf’ is required for DHCP.
device
bpf
# Berkeley packet filter
# USB support
device
uhci
# UHCI PCI->USB interface
device
ohci
# OHCI PCI->USB interface
device
ehci
# EHCI PCI->USB interface (USB 2.0)
device
usb
# USB Bus (required)
#device
udbp
# USB Double Bulk Pipe devices
device
ugen
# Generic
device
uhid
# “Human Interface Devices”
device
ukbd
# Keyboard
device
umass
# Disks/Mass storage - Requires scbus and
da
device
ums
# Mouse
# Specific to my Machine
device
atapicam
# for CD Writer to be detected by K3B and other CD writing
software
device
sound
# To Enable Sound
device
“snd_ad1816″
device
“snd_als4000″
device
snd_cmi
device
“snd_cs4281″
device
snd_csa
device
“snd_ds1″
device
“snd_emu10k1″
device
“snd_es137x”
device
snd_ess
device
“snd_fm801″
device
snd_gusc
device
snd_ich
device
snd_maestro
device
“snd_maestro3″
device
snd_mss
device
snd_neomagic
device
“snd_sb16″
device
snd_sbc
device
snd_solo
device
“snd_t4dwave”
device
“snd_via8233″
device
“snd_via82c686″
device
snd_vibes
device
snd_uaudio
device pcii
device
acpi
device
acpi_asus
device
acpi_video
device
cbb
# cardbus (yenta) bridge
device
pccard #
PC Card
(16-bit) bus
device
cardbus #
CardBus
(32-bit) bus
options DEVICE_POLLING
options HZ=1000
options PERFMON
device
apm_saver # Requires APM
options
AUTO_EOI_1
options AUTO_EOI_2
options VESA
