用busybox创建基于Linux2.6.24内核的nfs根文件系统

  一、主机环境
  Linux version 2.4.20-8, RedHat9, VMWare5.5.3;
  gcc version 3.4.4, Thread model: posix;
  GNU Make 3.81;
  arm-linux-gcc 4.2.1 （此创建过程见另贴 用crosstool脚本编译针对Linux2.6内核的交叉编译工具链 ）
  所需源文件：
  busybox-1.11.1.tar.bz2;

二、用Busybox创建nfs文件系统

1、解压busybox-1.11.1.tar.bz2，路径为
[root@Sure busybox-1.11.1]# pwd

/home/jacky/busybox-1.11.1

修改Makefilez中的ARCH和CROSS_COMPILE与本机的路径一致：

CROSS_COMPILE?= /opt/crosstool/bin/arm-s3c2410-linux-gnu- ... ARCH ?= arm

2、编译busybox。先make menuconfig，修改以下：

Busybox Settings--->     Build Options --->         [*] Build BusyBox as astatic binary (no shared libs)         //直接编译成静态库，省事点         (/opt/crosstool/bin/arm-s3c2410-linux-gnu-) Cross Compiler prefix         //这里和Makefile里保持一致，应该写一处就行了     Installation Options --->         [*] Don't use/usr         //不用本机的目录 Shells --->     Choose your default shell (ash) --->     //这里选择shell为ash，应该是默认选中的         --- ash         //把ash这档的选项全部选上

保存退出，直接make，make install。

3、用shell脚本创建根文件系统的目录结构，并在想要建立根文件系统的地方运行此脚本。我是用root用户登陆的，直接创建了设备节点。
[root@Sure root-s3c2410]# vim makedir.sh

#!/bin/sh   echo "makeing rootdir"   mkdir rootfs   cd rootfs   echo "makeing dir: bin dev etc lib proc sbin sys usr"   mkdir bin dev etc lib proc sbin sys usr #8 dirs   mkdir usr/bin usr/lib usr/sbin lib/modules #Don't use mknod, unless you runthis Script as   mknod -m 600 dev/console c 5 1   mknod -m 666 dev/null c 1 3   echo "making dir: mnt tmp var"   mkdir mnt tmp var   chmod 1777 tmp   mkdir mnt/etc mnt/jiffs2 mnt/yaffs mnt/data mnt/temp   mkdir var/lib var/lock var/log var/run var/tmp   chmod 1777 var/tmp   echo "making dir: home root boot"   mkdir home root boot   echo "done"

执行这个sh：
[root@Sure root-s3c2410]# sh makedir.sh
创建出一个主文件夹rootfs，里面有一批文件：
[root@Sure rootfs]# ls
bin  boot  dev  etc  home  lib  mnt  proc  root  sbin  sys  tmp  usr  var

4、把busybox源码目录下的etc的内容拷贝到这里的etc下
[root@Sure rootfs]# cd etc/
[root@Sure etc]# cp -a /home/jacky/busybox-1.11.1/examples/bootfloppy/etc/* ./

5、修改拷贝过来的profile文件
[root@Sure etc]# vim profile

#/etc/profile:system-wide.profile filefor the Bourne shells echo "Processing /etc/profile" # no-op # Set search library path echo " Set search library path" export LD_LIBRARY_PATH=/lib:/usr/lib # Set user path echo " Set user path" PATH=/bin:/sbin:/usr/bin:/usr/sbin export PATH # Set PS1 echo " Set PS1" HOSTNAME=`/bin/hostname` # 此处让shell提示符显示host名称的。是`，不是’，要注意 # 会在进入根系统后显示Jacky export PS1="\\e[32m[$USER@$HOSTNAME \\w\\a]\\$\\e[00;37m " # 此处\\e[32m是让后面的“[$USER@$HOSTNAME \\w\\a]”显示为绿色 # \\e[00是关闭效果 # \\e[05是闪烁 # 37m是让后面的显示为白色 # 多个命令可以；号隔开 echo "All done!" echo

6、修改初始化文件inittab和fstab
[root@Sure etc]# vim inittab

::sysinit:/etc/init.d/rcS ::respawn:-/bin/sh ::restart:/sbin/init tty2::askfirst:-/bin/sh ::ctrlaltdel:/bin/umount-a -r ::shutdown:/bin/umount-a -r ::shutdown:/sbin/swapoff –a

[root@Sure etc]# vim fstab

proc /proc proc defaults 0 0 none /tmp ramfs defaults 0 0 mdev /dev ramfs defaults 0 0 sysfs /sys sysfs defaults 0 0

7、修改初始化的脚本文件init.d/rcS
[root@Sure etc]# vim init.d/rcS

#!/bin/sh echo "Processing etc/init.d/rc.S" #hostname ${HOSTNAME} echo " Mount all" /bin/mount -a echo " Start mdev...." /bin/echo /sbin/mdev > proc/sys/kernel/hotplug mdev -s echo "****************************************************" echo " RootFS by NFS, s3c2410" echo " Created by Jacky Xu @ 2008.7.13" echo " Enjoy it!!!" echo "****************************************************" echo

8、创建一个空的mdev.conf文件，在挂载根文件系统时会用到的
[root@Sure etc]# touch mdev.conf

9、从本机拷贝passwd、shadow、group文件。
[root@Sure etc]# cp /etc/passwd .
[root@Sure etc]# cp /etc/shadow .
[root@Sure etc]# cp /etc/group .
修改passwd文件，把第一行和最后一行的bash修改成ash。

10、把busybox默认安装目录中的文件全部复制到这里的rootfs中。会发现多了linuxrc -> bin/busybox文件，这是挂载文件系统需要执行的。
[root@Sure etc]# cd ..
[root@Sure rootfs]# cp -Rfv /home/jacky/busybox-1.11.1/_install/ ./

OK，以上用busybox创建了一个基本的文件系统。
PS:
    如果编译busybox时选择动态库方式编译，则需要查看生成的busybox使用哪些动态库，然后把它们拷贝到rootfs/lib目录下。
[root@Sure lib]# arm-s3c2410-linux-gnu-readelf -d ../bin/busybox

Dynamic section at offset 0xc1014 contains 21 entries:   Tag Type Name/Value  0x00000001 (NEEDED) Shared library:[libm.so.6]  0x00000001 (NEEDED) Shared library:[libc.so.6]  0x0000000c (INIT) 0xc2ec  0x0000000d (FINI) 0xa96b8  0x00000004 (HASH) 0x80e8  0x00000005 (STRTAB) 0xa4c4  0x00000006 (SYMTAB) 0x8b64  0x0000000a (STRSZ) 3505(bytes)  0x0000000b (SYMENT) 16(bytes)  0x00000015 (DEBUG) 0x0  0x00000003 (PLTGOT) 0xd10e4  0x00000002 (PLTRELSZ) 3112(bytes)  0x00000014 (PLTREL) REL  0x00000017 (JMPREL) 0xb6c4  0x00000011 (REL) 0xb674  0x00000012 (RELSZ) 80(bytes)  0x00000013 (RELENT) 8(bytes)  0x6ffffffe (VERNEED) 0xb5a4  0x6fffffff (VERNEEDNUM) 2  0x6ffffff0 (VERSYM) 0xb276  0x00000000 (NULL) 0x0

可以看出，使用了libm.so.6和libc.so.6两个库。发现只拷贝这两个库还不够，还需要ld-linux.so.2和libgcc_s.so.1，也就是我编译出来的这个busybox需要4个动态库文件。
# cp /opt/crosstool/arm-s3c2410-linux-gnu/sys-root/lib/libm.so.6 .
# cp /opt/crosstool/arm-s3c2410-linux-gnu/sys-root/lib/libc.so.6 .
# cp /opt/crosstool/arm-s3c2410-linux-gnu/sys-root/lib/ld-linux.so.2 .
# cp /opt/crosstool/arm-s3c2410-linux-gnu/lib/libgcc_s.so.1 .
这样，使用动态库可以节省一半左右的空间，不过效率有所降低。

三、测试
1、在本机修改/etc/export文件，重启NFS服务：
[root@Sure rootfs]# vim /etc/exports
/home/jacky/root-s3c2410/rootfs 192.168.1.*(rw,sync,no_root_squash)
[root@Sure rootfs]# service nfs restart

2、在Bootloader中传递以下参数给Kernel：
root=/dev/nfs rw nfsroot=192.168.1.249:/home/jacky/root-s3c2410/rootfs ip=192.168.1.199:192.168.1.249:192.168.1.1:255.255.255.0:Jacky:eth0:off console=ttySAC0,115200 init=/linuxrc noinitrd

3、启动目标板，串口输出显示根文件系统已经加载成功：

Boot Parameters: root=/dev/nfs rw nfsroot=192.168.1.249:/home/jacky/root-s3c2410/rootfs ip=192.168.1.199:192.168.1.249:192.168.1.1:255.255.255.0:Jacky:eth0:off console=ttySAC0,115200 init=/linuxrc noinitrd Now, booting Linux... Uncompressing Linux........................................................................................................... done, booting the kernel. Linux version 2.6.24.7(root@Sure)(gcc version 4.2.1)#5 Sat Jul 12 17:26:16 CST 2008 CPU: ARM920T [41129200] revision 0(ARMv4T), cr=c0007177 Machine: SMDK2410 ATAG_INITRD is deprecated; please update your bootloader. Memory policy: ECC disabled, Data cache writeback CPU S3C2410A (id 0x32410002) S3C2410: core 200.000 MHz, memory 100.000 MHz, peripheral 50.000 MHz S3C24XX Clocks, (c) 2004 Simtec Electronics CLOCK: Slow mode(1.500 MHz), fast, MPLL on, UPLL on CPU0: D VIVT write-back cache CPU0: I cache: 16384 bytes, associativity 64, 32 byte lines, 8 sets CPU0: D cache: 16384 bytes, associativity 64, 32 byte lines, 8 sets Built 1 zonelists in Zone order, mobility grouping on. Total pages: 16256 Kernel command line: root=/dev/nfs rw nfsroot=192.168.1.249:/home/jacky/root-s3c2410/rootfs ip=192.168.1.199:192.168.1.249:192.168.1.1:255.255.255.0:Jacky:eth0:off console=ttySAC0,115200 init=/linuxrc noinitrd irq: clearing subpending status 00000003 PID hash table entries: 256 (order: 8, 1024 bytes) timer tcon=00000000, tcnt a2c1, tcfg 00000200,00000000, usec 00001eb8 Console: colour dummy device 80x30 console [ttySAC0] enabled Dentry cache hash table entries: 8192 (order: 3, 32768 bytes) Inode-cache hash table entries: 4096(order: 2, 16384 bytes) Memory: 64MB = 64MB total Memory: 61440KB available (3048K code, 314K data, 128K init) Mount-cache hash table entries: 512 CPU: Testing write buffer coherency: ok net_namespace: 64 bytes NET: Registered protocol family 16 S3C2410 Power Management, (c) 2004 Simtec Electronics S3C2410: Initialising architecture S3C24XX DMA Driver, (c) 2003-2004,2006 Simtec Electronics DMA channel 0 at c4800000, irq 33 DMA channel 1 at c4800040, irq 34 DMA channel 2 at c4800080, irq 35 DMA channel 3 at c48000c0, irq 36 usbcore: registered new interface driver usbfs usbcore: registered new interface driver hub usbcore: registered new device driver usb Bluetooth: Core ver 2.11 NET: Registered protocol family 31 Bluetooth: HCI device and connection manager initialized Bluetooth: HCI socket layer initialized NET: Registered protocol family 2 IP route cache hash table entries: 1024 (order: 0, 4096 bytes) TCP established hash table entries: 2048 (order: 2, 16384 bytes) TCP bind hash table entries: 2048(order: 1, 8192 bytes) TCP: Hash tables configured (established 2048 bind 2048) TCP reno registered NetWinder Floating Point Emulator V0.97 (double precision) JFFS2 version 2.2.(NAND) © 2001-2006 Red Hat, Inc. JFS: nTxBlock = 480, nTxLock= 3840 io scheduler noop registered io scheduler anticipatory registered (default) io scheduler deadline registered io scheduler cfq registered s3c2410-lcd s3c2410-lcd: no platform datafor lcd, cannot attach s3c2410-lcd: probe of s3c2410-lcd failed witherror -22 lp: driver loaded but no devices found ppdev: user-space parallel port driver Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing enabled s3c2410-uart.0: s3c2410_serial0 at MMIO 0x50000000(irq = 70) is a S3C2410 s3c2410-uart.1: s3c2410_serial1 at MMIO 0x50004000(irq = 73) is a S3C2410 s3c2410-uart.2: s3c2410_serial2 at MMIO 0x50008000(irq = 76) is a S3C2410 RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize loop: module loaded Cirrus Logic CS8900A driver for Linux (Modified for SMDK2410) eth0: CS8900A rev E at 0xe0000300 irq=53, addr: 00: 0:3E:26:0A: 0 Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2 ide: Assuming 50MHz system bus speed for PIO modes; override with idebus=xx S3C24XX NAND Driver, (c) 2004 Simtec Electronics s3c2410-nand s3c2410-nand: Tacls=3, 30ns Twrph0=7 70ns, Twrph1=3 30ns NAND device: Manufacturer ID: 0xec, Chip ID: 0x76(Samsung NAND 64MiB 3,3V 8-bit) Scanning device for bad blocks Creating 5 MTD partitions on "NAND 64MiB 3,3V 8-bit": 0x00000000-0x00100000 : "Bootloader" 0x00100000-0x00400000 : "Kernel" 0x00400000-0x03400000 : "Root" 0x03400000-0x03fe0000 : "ExtRoot" 0x03fe0000-0x04000000 : "Param" usbmon: debugfs is not available s3c2410-ohci s3c2410-ohci: S3C24XX OHCI s3c2410-ohci s3c2410-ohci:new USB bus registered, assigned bus number 1 s3c2410-ohci s3c2410-ohci: irq 42, io mem 0x49000000 usb usb1: configuration #1 chosen from 1 choice hub 1-0:1.0: USB hub found hub 1-0:1.0: 2 ports detected mice: PS/2 mouse device commonfor all mice S3C24XX RTC, (c) 2004,2006 Simtec Electronics s3c2410-i2c s3c2410-i2c: slave address 0x10 s3c2410-i2c s3c2410-i2c: bus frequencyset to 390 KHz s3c2410-i2c s3c2410-i2c: i2c-0: S3C I2C adapter S3C2410 Watchdog Timer, (c) 2004 Simtec Electronics s3c2410-wdt s3c2410-wdt: watchdog inactive,reset disabled, irq enabled TCP cubic registered NET: Registered protocol family 1 NET: Registered protocol family 17 RPC: Registered udp transport module. RPC: Registered tcp transport module. drivers/rtc/hctosys.c: unable toopen rtc device (rtc0) IP-Config: Complete:       device=eth0, addr=192.168.1.199, mask=255.255.255.0, gw=192.168.1.1,      host=Jacky, domain=, nis-domain=(none),      bootserver=192.168.1.249, rootserver=192.168.1.249, rootpath= Looking up port of RPC 100003/2 on 192.168.1.249 Looking up port of RPC 100005/1 on 192.168.1.249 VFS: Mounted root (nfs filesystem). Freeing init memory: 128K init started: BusyBox v1.11.1(2008-07-13 14:46:21 CST) starting pid 789, tty '': '/etc/init.d/rcS' Processing etc/init.d/rc.S   Mount all   Start mdev.... ****************************************************               RootFS by NFS, s3c2410          Created by Jacky Xu @ 2008.7.13                    Enjoy **************************************************** starting pid 793, tty '': '-/bin/sh' Processing /etc/profile   Set search library path   Set user path   Set PS1 All [root@Jacky /]# ls bin dev home linuxrc proc sbin tmp var boot etc lib mnt root sys usr [root@Jacky /]# 为了减少运行时库的大小，我们应该使用交叉编译版本即arm-linux-gcc 的strip工具来处理根文件系统的库文件，把二进制文件中的包含的符号表和调试信息删除掉。 例： #arm-linux-strip /home/su/rootfs/lib/*.so 交叉编译器4.3.2的lib哪里觅？？ 之前将usr/local/arm/4.3.2/arm-non-linux-gnueabi/libc/lib下的*.so文件一股脑儿copy到rootfs/lib/下，结果下载后返回“Kernel panic - not syncing: Attempted to kill init!”出错信息。后来终于想到可能是库链接出问题，重新复制usr/local/arm/4.3.2/arm-non-linux-gnueabi/libc/armv4t/lib下的文件，问题解决！

已经直接进入了nfs文件系统！