# cd /usr/src/sys/i386/conf
# cp GENERIC GENERIC.20060812
# ee GENERIC
如果要加入ipf防火墙的话则加入
options IPFIREWALL
options IPFIREWALL_DEFAULT_TO_ACCEPT
options IPFIREWALL_FORWARD
options IPDIVERT
# cd /usr/src/sys/i386/conf
运行config命令来产生内核源代码。
# /usr/sbin/config GENERIC
切换到建立内核的目录。
# cd ../compile/GENERIC
编译内核
# make cleandepend (最好先清除一下)
# make depend
# make
安装新内核。
# make install
OK,到这里，如果中间没有出现任何错误的话，那么我们的内核心就已经安装成功了，
reboot后就能够使用我们的新编译的内核了。如果出现了
错误，那么请检查你的步骤是否跟上面的步骤一致，同时要检查你的内核配置文件配置的是否正确，
一般编译不成功都是内核文件配置的问题
，请仔细检查。
四、新内核无法启动：
如果你编译的内核无法启动，那么可以使用以前的内核来启动。一般编译一次内核后，
都会把把旧内核备份，一般/boot/kernel.old就是旧内
核的备份，出现问题就能够使用久内核来启动。
具体实现方法是：
你可以在系统启动进行10计数的时候按Enter以外的任何键， 接着键入unload命令，
再键入boot kernel.old，或者任何能正常启动的内核名字
，然后就能够正常启动系统，进入系统后再重新进行内核的配置工作。
注意： 你不能仅依靠kernel.old，因为当你安装一个新内核时，
kernel.old会被上一次安装的内核所覆盖，所以你要么自己手动备份一个能
正常启动的内核，或者注意你的kernel.old是否能正常启动的内核。
结束
好，到这里，我们的编译内核的工作就完成了，来然我们来看看我们的内核是否已经减小了：
# ls -l /boot/kernel/kernel
-r-xr-xr-x 1 root wheel 3090929 Sep 1 21:30 /boot/kernel/kernel
呵呵，明显把原来的5940286变成了现在的3090929，虽然没有变小一倍，
但是也变小好多啦，以后系统又更快啦
修改时请参http://cnsnap.cn.freebsd.org/doc/zh_CN.GB2312/books/handbook/kernelconfig-config.html
#######################################################################
machine i386
cpu I486_CPU
cpu I586_CPU
cpu I686_CPU
ident GENERIC
# To statically compile in device wiring instead of /boot/device.hints
#hints "GENERIC.hints" # Default places to look for devices.
makeoptions DEBUG=-g # Build kernel with gdb(1) debug symbols
#options SCHED_ULE # ULE scheduler
options SCHED_4BSD # 4BSD scheduler
options PREEMPTION # Enable kernel thread preemption
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 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 COMPAT_FREEBSD5 # Compatible with FreeBSD5
#options SCSI_DELAY=5000 # 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.
options IPFIREWALL
options IPFIREWALL_DEFAULT_TO_ACCEPT
options IPFIREWALL_FORWARD
device apic # I/O APIC
# Bus support.
device eisa
device pci
# Floppy drives
device fdc
# ATA and ATAPI devices
device ata
device atadisk # ATA disk drives
device ataraid # ATA RAID drives
device atapicd # ATAPI CDROM drives
device atapifd # ATAPI floppy drives
device atapist # ATAPI tape drives
options ATA_STATIC_ID # Static device numbering
# SCSI Controllers
#device ahb # EISA AHA1742 family
#device ahc # AHA2940 and onboard AIC7xxx devices
#device ahd # AHA39320/29320 and onboard AIC79xx devices
#device amd # AMD 53C974 (Tekram DC-390(T))
#device isp # Qlogic family
#device ispfw # Firmware for QLogic HBAs- normally a module
#device mpt # LSI-Logic MPT-Fusion
#device ncr # NCR/Symbios Logic
#device sym # NCR/Symbios Logic (newer chipsets + those of `ncr’)
#device trm # Tekram DC395U/UW/F DC315U adapters
#device adv # Advansys SCSI adapters
#device adw # Advansys wide SCSI adapters
#device aha # Adaptec 154x SCSI adapters
#device aic # Adaptec 15[012]x SCSI adapters, AIC-6[23]60.
#device bt # Buslogic/Mylex MultiMaster SCSI adapters
#device ncv # NCR 53C500
#device nsp # Workbit Ninja SCSI-3
#device stg # TMC 18C30/18C50
# SCSI peripherals
#device scbus # SCSI bus (required for SCSI)
#device ch # SCSI media changers
#device da # Direct Access (disks)
#device sa # Sequential Access (tape etc)
#device cd # CD
#device pass # Passthrough device (direct SCSI access)
#device ses # SCSI Environmental Services (and SAF-TE)
# RAID controllers interfaced to the SCSI subsystem
#device amr # AMI MegaRAID
#device arcmsr # Areca SATA II RAID
#device asr # DPT SmartRAID V, VI and Adaptec SCSI RAID
#device ciss # Compaq Smart RAID 5*
#device dpt # DPT Smartcache III, IV – See NOTES for options
#device hptmv # Highpoint RocketRAID 182x
#device iir # Intel Integrated RAID
#device ips # IBM (Adaptec) ServeRAID
#device mly # Mylex AcceleRAID/eXtremeRAID
#device twa # 3ware 9000 series PATA/SATA RAID
# RAID controllers
#device aac # Adaptec FSA RAID
#device aacp # SCSI passthrough for aac (requires CAM)
#device ida # Compaq Smart RAID
#device mlx # Mylex DAC960 family
#device pst # Promise Supertrak SX6000
#device twe # 3ware ATA RAID
# 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
# Power management support (see NOTES for more options)
#device apm
# Add suspend/resume support for the i8254.
device pmtimer
# PCCARD (PCMCIA) support
# PCMCIA and cardbus bridge support
#device cbb # cardbus (yenta) bridge
#device pccard # PC Card (16-bit) bus
#device cardbus # CardBus (32-bit) bus
# Serial (COM) ports
#device sio # 8250, 16[45]50 based serial ports
# Parallel port
device ppc
device ppbus # Parallel port bus (required)
device lpt # Printer
device plip # TCP/IP over parallel
device ppi # Parallel port interface device
#device vpo # Requires scbus and da
# If you’ve got a "dumb" serial or parallel PCI card that is
# supported by the puc(4) glue driver, uncomment the following
# line to enable it (connects to the sio and/or ppc drivers):
#device puc
# PCI Ethernet NICs.
#device de # DEC/Intel DC21×4x (“Tulip”)
#device em # Intel PRO/1000 adapter Gigabit Ethernet Card
#device ixgb # Intel PRO/10GbE Ethernet Card
#device txp # 3Com 3cR990 (“Typhoon”)
#device vx # 3Com 3c590, 3c595 (“Vortex”)
# 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 bfe # Broadcom BCM440x 10/100 Ethernet
#device bge # Broadcom BCM570xx Gigabit Ethernet
#device dc # DEC/Intel 21143 and various workalikes
#device fxp # Intel EtherExpress PRO/100B (82557, 82558)
#device lge # Level 1 LXT1001 gigabit Ethernet
#device nge # NatSemi DP83820 gigabit Ethernet
#device nve # nVidia nForce MCP on-board Ethernet Networking
#device pcn # AMD Am79C97x PCI 10/100(precedence over ‘lnc’)
#device re # RealTek 8139C+/8169/8169S/8110S
device rl # RealTek 8129/8139
#device sf # Adaptec AIC-6915 (“Starfire”)
#device sis # Silicon Integrated Systems SiS 900/SiS 7016
#device sk # SysKonnect SK-984x & SK-982x gigabit Ethernet
#device ste # Sundance ST201 (D-Link DFE-550TX)
#device ti # Alteon Networks Tigon I/II gigabit Ethernet
#device tl # Texas Instruments ThunderLAN
#device tx # SMC EtherPower II (83c170 “EPIC”)
#device vge # VIA VT612x gigabit Ethernet
#device vr # VIA Rhine, Rhine II
#device wb # Winbond W89C840F
#device xl # 3Com 3c90x (“Boomerang”, “Cyclone”)
# ISA Ethernet NICs. pccard NICs included.
#device cs # Crystal Semiconductor CS89×0 NIC
# ‘device ed’ requires ‘device miibus’
#device ed # NE[12]000, SMC Ultra, 3c503, DS8390 cards
#device ex # Intel EtherExpress Pro/10 and Pro/10+
#device ep # Etherlink III based cards
#device fe # Fujitsu MB8696x based cards
#device ie # EtherExpress 8/16, 3C507, StarLAN 10 etc.
#device lnc # NE2100, NE32-VL Lance Ethernet cards
#device sn # SMC’s 9000 series of Ethernet chips
#device xe # Xircom pccard Ethernet
# ISA devices that use the old ISA shims
#device le
# Wireless NIC cards
#device wlan # 802.11 support
#device an # Aironet 4500/4800 802.11 wireless NICs.
#device awi # BayStack 660 and others
#device ral # Ralink Technology RT2500 wireless NICs.
#device wi # WaveLAN/Intersil/Symbol 802.11 wireless NICs.
#device wl # Older non 802.11 Wavelan wireless NIC.
# Pseudo devices.
device loop # Network loopback
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 ulpt # Printer
#device umass # Disks/Mass storage – Requires scbus and da
device ums # Mouse
#device ural # Ralink Technology RT2500USB wireless NICs
#device urio # Diamond Rio 500 MP3 player
#device uscanner # Scanners
## USB Ethernet, requires miibus
#device aue # ADMtek USB Ethernet
#device axe # ASIX Electronics USB Ethernet
#device cdce # Generic USB over Ethernet
#device cue # CATC USB Ethernet
#device kue # Kawasaki LSI USB Ethernet
#device rue # RealTek RTL8150 USB Ethernet
# FireWire support
#device firewire # FireWire bus code
#device sbp # SCSI over FireWire (Requires scbus and da)
#device fwe # Ethernet over FireWire (non-standard!)
#######################################################################