转自：http://www.linuxidc.com/Linux/2012-09/70510p2.htm
三、根文件系统的制作
我们利用busybox来制作根文件系统
1．在下列网站下载busybox-1.15.0.tar.bz2
http://www.linuxidc.com/linux/2011-08/40704.htm
在当前目录下解压busybox
tar -jxvf busybox-1.15.0.tar.bz2
2．配置编译busybox
使用menuconfig来配置busybox：
make menuconfig
修改下列内容：
Busybox Settings --->
Build Options --->
[*] Build BusyBox as a staticbinary (no shared libs) (编译成静态库)
Busybox Library Tuning --->
[*] Tabcompletion (tab缩进功能)
[*] Usernamecompletion
[*] Fancy shellprompts (这两项在创建/etc/profile文件时要用，这样可以命令行有提示符显示)
只需修改上述几个选项，其他配置可以不去改动。
修改Makefile
emacsMakefile
在第164行，改为：
CROSS_COMPILE?=arm-linux-
在第190行，改为：
ARCH ?=arm
执行make命令编译busybox
3．利用下面命令安装busybox：
Make CONFIG_PREFIX=/home/zhaocj/rootfs install
其中/home/zhaocj/rootfs为指定的安装目录，如果还没有该目录，则需先要用mkdir命令创建该目录。之所以要指定目录，就是为了改变系统默认生成的_stall目录。
安装完毕后，会在/home/zhaocj/rootfs目录下生成bin、linuxrc、sbin、usr这四个目录和文件。
4．进入rootfs目录，自行添加其他目录和文件
首先要创建etc目录，以及在该目录下生成四个文件：etc/inittab、etc/fstab、etc/profile、etc/init.d/rcS
mkdir etc
cd etc
emacs inittab
内容为：
::sysinit:/etc/init.d/rcS
::askfirst:-/bin/sh
::restart:/sbin/init
::ctrlaltdel:/sbin/reboot
::shutdown:umount-a -r
emacs fstab
内容为：
#device mount-point type options dump fsck order
proc /proc proc defaults 0 0
sysfs /sys sysfs defaults 0 0
tmpfs /temp tmpfs defaults 0 0
tmpfs /dev tmpfs defaults 0 0
emacs profile
内容为：
#!/bin/sh
exportHOSTNAME=zhaocj
exportUSER=root
exportHOME=root
exportPS1="[$USER@$HOSTNAME \W]\#"
PATH=/bin:/sbin:/usr/bin:/usr/sbin
LD_LIBRARY_PATH=/lib:/usr/lib:$LD_LIBRARY_PATH
exportPATH LD_LIBRARY_PAT
mkdir init.d
emacs init.d/rcS
内容为：
mount -a
mkdir/dev/pts
mount -tdevpts devpts /dev/pts
echo/sbin/mdev > /proc/sys/kernel/hotplug
mdev -s
在根用户下增加该文件的执行权限
chmod +xrcS
回到主目录下，创建其他目录：
mkdir dev home temp proc sys
进入dev目录，并用根用户创建两个基本的设备文件：
mknod console c 5 1
mknod null c 1 3
至此，根文件系统创建完毕。
5．生成cramfs根文件系统
在这里我们要使用cramfs根文件系统，并把它烧写到nandflash中，因此要有编译cramfs的制作工具。在下列网站下载cramfs-1.1.tar.gz。
http://sourceforge.net/projects/cramfs/
在当前目录下解压cramfs-1.1.tar.gz，并编译：
tar zxvfcramfs-1.1.tar.gz
make
编译完成后，会生成mkcramfs和cramfsck两个可执行文件，其中mkcramfs工具是用来创建cramfs文件系统的。
利用mkcramfs压缩根文件系统，生成cramfs：
mkcramfs rootfs root-cramfs
rootfs为刚刚制作的根文件系统的目录，root-cramfs为最终生成的cramfs根文件系统。
6．最后，我们把root-cramfs文件烧写到nandflash中的0x800000至0x1000000中。
当完成以上三个部分内容后，uboot就能够正确引导linux内核以及加载根文件系统了。下面列出了uboot启动后在串口显示的内容：
U-Boot2011.06 (Aug 31 2012 - 15:08:19)
DRAM: 64 MiB
Flash: ##Unknown flash on Bank 1 - Size = 0x00000000 = 0 MB
2 MiB
NAND: 256 MiB
***Warning - bad CRC, using default environment
In: serial
Out: serial
Err: serial
Net: dm9000
Hit anykey to stop autoboot: 0
NANDread: device 0 offset 0x200000, size 0x400000 4194304 bytes read: OK
##Booting kernel from Legacy Image at 31000000 ...
Image Name: linux
Created: 2012-09-01 14:46:43 UTC
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 2428888 Bytes = 2.3 MiB
Load Address: 31000000
Entry Point: 31000040
Verifying Checksum ... OK
XIP Kernel Image ... OK
OK
Startingkernel ...
UncompressingLinux... done, booting the kernel.
BootingLinux on physical CPU 0
Linuxversion 3.4.6 (zcj@qihao) (gcc version 4.2.2) #3Sat Sep 1 22:44:40 CST 2012
CPU:ARM920T [41129200] revision 0 (ARMv4T), cr=00007177
CPU: VIVTdata cache, VIVT instruction cache
Machine:SMDK2440
Memorypolicy: ECC disabled, Data cache writeback
CPU S3C2440A(id 0x32440001)
S3C24XX Clocks, Copyright 2004 SimtecElectronics
S3C244X: core 400.000 MHz, memory 100.000MHz, peripheral 50.000 MHz
CLOCK:Slow mode (1.500 MHz), fast, MPLL on, UPLL on
Built 1zonelists in Zone order, mobility grouping on. Total pages: 16256
Kernelcommand line: root=/dev/mtdblock3 ro noinitrd init=/linuxrcconsole=ttySAC,115200 rootfstype=cramfs mem=64M
PID hashtable entries: 256 (order: -2, 1024 bytes)
Dentrycache hash table entries: 8192 (order: 3, 32768 bytes)
Inode-cachehash table entries: 4096 (order: 2, 16384 bytes)
Memory:64MB = 64MB total
Memory:59980k/59980k available, 5556k reserved, 0K highmem
Virtualkernel memory layout:
vector : 0xffff0000 - 0xffff1000 ( 4 kB)
fixmap : 0xfff00000 - 0xfffe0000 ( 896kB)
vmalloc : 0xc4800000 - 0xff000000 ( 936 MB)
lowmem : 0xc0000000 - 0xc4000000 ( 64 MB)
modules : 0xbf000000 - 0xc0000000 ( 16MB)
.text : 0xc0108000 - 0xc0545868 (4343 kB)
.init : 0xc0546000 - 0xc0570000 ( 168 kB)
.data : 0xc0570000 - 0xc05a67a0 ( 218 kB)
.bss : 0xc05a67c4- 0xc05cf1dc ( 163 kB)
NR_IRQS:99
irq:clearing subpending status 00000002
sched_clock:32 bits at 200 Hz, resolution 5000000ns, wraps every 4294967291ms
Console:colour dummy device 80x30
Calibratingdelay loop... 49.56 BogoMIPS (lpj=123904)
pid_max:default: 32768 minimum: 301
Mount-cachehash table entries: 512
CPU:Testing write buffer coherency: ok
Settingup static identity map for 0x304355a0- 0x3043561c
gpiochip_add:registered GPIOs 0 to 23 on device: GPIOA
gpiochip_add:registered GPIOs 32 to 47 on device: GPIOB
gpiochip_add:registered GPIOs 64 to 79 on device: GPIOC
gpiochip_add:registered GPIOs 96 to 111 on device: GPIOD
gpiochip_add:registered GPIOs 128 to 143 on device: GPIOE
gpiochip_add:registered GPIOs 160 to 167 on device: GPIOF
gpiochip_add:registered GPIOs 192 to 207 on device: GPIOG
gpiochip_add:registered GPIOs 224 to 234 on device: GPIOH
gpiochip_add:registered GPIOs 256 to 271 on device: GPIOJ
NET:Registered protocol family 16
S3C Power Management, Copyright 2004Simtec Electronics
S3C2440: Initialising architecture
S3C2440: IRQ Support
S3C244X: Clock Support, DVS off
bio:create slab <bio-0> at 0
SCSIsubsystem initialized
usbcore:registered new interface driver usbfs
usbcore:registered new interface driver hub
usbcore:registered new device driver usb
s3c-i2cs3c2440-i2c: slave address 0x10
s3c-i2cs3c2440-i2c: bus frequency set to 97 KHz
s3c-i2cs3c2440-i2c: i2c-0:S3C I2C adapter
AdvancedLinux Sound Architecture Driver Version 1.0.25.
NET:Registered protocol family 2
IP routecache hash table entries: 1024 (order: 0, 4096 bytes)
TCPestablished hash table entries: 2048 (order: 2, 16384 bytes)
TCP bindhash table entries: 2048 (order: 1, 8192 bytes)
TCP: Hashtables configured (established 2048 bind 2048)
TCP: reno registered
UDP hashtable entries: 256 (order: 0, 4096 bytes)
UDP-Litehash table entries: 256 (order: 0, 4096 bytes)
NET:Registered protocol family 1
RPC:Registered named UNIX socket transport module.
RPC:Registered udp transport module.
RPC:Registered tcp transport module.
RPC:Registered tcp NFSv4.1 backchannel transport module.
NetWinderFloating Point Emulator V0.97 (extended precision)
jffs2:version 2.2. (NAND) (SUMMARY) ?2001-2006 Red Hat, Inc.
ROMFS MTD(C) 2007 Red Hat, Inc.
msgmnihas been set to 117
ioscheduler noop registered
ioscheduler deadline registered
ioscheduler cfq registered (default)
Console:switching to colour frame buffer device 30x40
fb0: s3c2410fb frame buffer device
Serial:8250/16550 driver, 4 ports, IRQ sharing enabled
s3c2440-uart.0: ttySAC0 at MMIO 0x50000000(irq = 70) is a S3C2440
console[ttySAC0] enabled
s3c2440-uart.1: ttySAC1 at MMIO 0x50004000(irq = 73) is a S3C2440
s3c2440-uart.2: ttySAC2 at MMIO 0x50008000(irq = 76) is a S3C2440
lp:driver loaded but no devices found
ppdev:user-space parallel port driver
brd:module loaded
loop:module loaded
UniformMulti-Platform E-IDE driver
ide-gddriver 1.18
ide-cddriver 5.00
S3C24XX NAND Driver, (c) 2004 SimtecElectronics
s3c24xx-nand s3c2440-nand: Tacls=2, 20ns Twrph0=6 60ns, Twrph1=220ns
s3c24xx-nand s3c2440-nand: NAND ECC disabled
NANDdevice: Manufacturer ID: 0xec, Chip ID: 0xda (Samsung NAND 256MiB 3,3V 8-bit)
NAND_ECC_NONEselected by board driver. This is not recommended!
Scanningdevice for bad blocks
Baderaseblock 615 at 0x000004ce0000
Baderaseblock 807 at 0x0000064e0000
Creating4 MTD partitions on "NAND":
0x000000000000-0x000000080000: "UBoot"
0x000000080000-0x000000100000: "Para"
0x000000200000-0x000000600000: "Kernel"
0x000000800000-0x000001000000: "rootfs"
dm9000Ethernet Driver, V1.31
ohci_hcd:USB 1.1 'Open' Host Controller (OHCI) Driver
s3c2410-ohci s3c2410-ohci: S3C24XXOHCI
s3c2410-ohci s3c2410-ohci: new USB bus registered, assigned busnumber 1
s3c2410-ohci s3c2410-ohci: irq 42, io mem 0x49000000
hub1-0:1.0: USB hub found
hub1-0:1.0: 2 ports detected
usbcore:registered new interface driver libusual
usbcore:registered new interface driver usbserial
usbcore:registered new interface driver usbserial_generic
USBSerial support registered for generic
usbserial:USB Serial Driver core
usbcore:registered new interface driver ftdi_sio
USB Serialsupport registered for FTDI USB Serial Device
ftdi_sio:v1.6.0:USB FTDI Serial Converters Driver
usbcore:registered new interface driver pl2303
USBSerial support registered for pl2303
mousedev:PS/2 mouse device common for all mice
s3c2410_wdt: S3C2410 Watchdog Timer, (c) 2004 Simtec Electronics
s3c2410-wdt s3c2410-wdt: watchdog inactive, reset disabled, irqdisabled
TCP:cubic registered
NET:Registered protocol family 17
drivers/rtc/hctosys.c:unable to open rtc device (rtc0)
ALSAdevice list:
No soundcards found.
VFS:Mounted root (cramfs filesystem) readonly on device 31:3.
Freeinginit memory: 168K
Pleasepress Enter to activate this console.
当我们按下回车键后，会看到linux的提示符：
[root@zhaocj /]#
在该提示符下就可以运行一些linux命令了，如：
[root@zhaocj /]#ls
bin etc lib proc sys usr
dev home linuxrc sbin temp
相关阅读：
U-Boot源代码下载地址 http://www.linuxidc.com/Linux/2011-07/38897.htm
U-Boot-2011.06启动流程分析 http://www.linuxidc.com/Linux/2011-07/39310.htm
u-boot-2011.06在基于s3c2440开发板的移植之编译配置 http://www.linuxidc.com/Linux/2011-10/45455.htm
u-boot-2011.06在基于s3c2440开发板的移植之NorFlash启动 http://www.linuxidc.com/Linux/2011-10/45456.htm
u-boot-2011.06在基于S3C2440开发板的移植之解决raise: Signal # 8 caught http://www.linuxidc.com/Linux/2011-10/454554.htm
u-boot-2011.06在基于s3c2440开发板的移植之支持NandFlash读写 http://www.linuxidc.com/Linux/2011-10/45457.htm
u-boot-2011.06在基于s3c2440开发板的移植之硬件ECC http://www.linuxidc.com/Linux/2011-10/454558.htm
u-boot-2011.06在基于s3c2440开发板的移植之DM9000 http://www.linuxidc.com/Linux/2012-09/70507.htm
u-boot-2011.06在基于s3c2440开发板的移植之nandflash启动 http://www.linuxidc.com/Linux/2012-09/70508.htm
u-boot-2011.06在基于s3c2440开发板的移植之支持YAFFS2 http://www.linuxidc.com/Linux/2012-09/70509.htm
u-boot-2011.06在基于s3c2440开发板的移植之引导内核与加载根文件系统 http://www.linuxidc.com/Linux/2012-09/70510.htm
u-boot-2011.06在基于s3c2440开发板的移植之结束篇 http://www.linuxidc.com/Linux/2012-09/70511.htm