ramdisk 製作：

1： 核心支援：
其中主要修改3項，如下：
①、修改Bootoptions
Default kernel command string  這一項我設為空，讓bootloader(u-boot,vivi)傳入。

②、選上 Float point emulation ->
[ * ] NWFE math emnulaiton

③、修改Driver device  ->
  Block device ->
(4096)Default RAM disk size (kbytes)
改4096為8192

2：以下是摘自網上的，

製作空的ramdisk：
# dd if=/dev/zero of=ramdisk bs=1k count=8000
   在本地目錄下出現一個rmdisk的塊檔案
# losetup /dev/loop2 ramdisk
# mkfs.ext2 /dev/loop2
掛載ramdisk至/mnt下
# mount -t ext2 /dev/loop2 /mnt
㈢．準備lib庫檔案
# cd /mnt
# mkdir lib
# cd  /usr/local/arm/3.4.1/arm-linux/lib
# for file in libc libcrypt libdl libm libpthread libresolv libutil
> do
> cp $file-*.so /mnt/lib
> cp -d $file.so.[*0-9] /mnt/lib
> done
# cp -d ld*.so* /mnt/lib

㈣．複製busybox檔案至ramdisk中：
# cp –rf  /busybox-1.2.2.1 <script src="http://pagead2.googlesyndication.com/pagead/show_ads.js" type="text/javascript"></script> /_install/* /mnt/
這樣在ramdisk中就有：sbin linuxrc bin
㈤.
# umount /dev/loop2
# losetup -d /dev/loop2
# gzip -9  ramdisk

這樣ramdisk.gz就製作好了。
# cp ramdisk.gz /tftpboot

基本上我也是如法炮製， 不過我是直接拿上次nfs啟動的檔案系統的內容全部拷貝到這裡，
注意拷貝連結檔案時要加上引數-d， 同時參閱了hh bbs上的說要
在ramdisk中建立console和null即可
cd /dev
mknod -m 660 console c 5 1
mknod -m 660 null c 1 3

同時我的檔名字叫做today.ramfs.gz

試驗： 在uboot中設定
setenv bootargs "console=ttySAC0 initrd=0x30800000,0x440000 root=/dev/ram init=/linuxrc"
或
setenv bootargs "console=ttySAC0 initrd=0x30800000,0x440000 root=/dev/rd/0 init=/linuxrc"
按Document/initrd.txt中說如果採用devfs，則應使用root=/dev/rd/0， 如不採用，則用/dev/ram  ，結果反覆試驗了一下， 兩個效果是一樣的。
uboot==>tftp 30008000 zImage;tftp 30800000 today.ramfs.gz;go 30008000

發現：Uncompressing Linux......................................................................
就不動了， 查看了一下,核心沒什麼問題， 由昨天做nfs檔案系統記起來了linuxrc檔案， 一看是一個shell指令碼，
就把busybox生成的linuxrc拷貝過來，覆蓋掉。

                                                                                       
U-Boot 1.1.4 (Jan 13 2007 - 18:54:16)
                                                                                       
U-Boot code: 33F80000 -> 33F9DA78  BSS: -> 33FA20E8
RAM Configuration:
Bank #0: 30000000 64 MB
Nor Flash: 512 kB
Nand Flash:    64 MB
                                                                                       
In:    serial
Out:   serial
Err:   serial
hujun2410=> tftp 30008000 zImage;tftp 30800000 today.ramfs.gz;go 30008000
TFTP from server 59.69.74.87; our IP address is 59.69.75.186
Filename 'zImage'.
Load address: 0x30008000
Loading: #################################################################
        #################################################################
        #################################################################
        #################################################################
done
Bytes transferred = 1326596 (143e04 hex)
TFTP from server 59.69.74.87; our IP address is 59.69.75.186
Filename 'today.ramfs.gz'.
Load address: 0x30800000
Loading: #################################################################
        #################################################################
        #################################################################
        #################################################################
        #################################################################
        #################################################################
        #################################################################
        #################################################################
        ###################################
done
Bytes transferred = 2839962 (2b559a hex)
## Starting application at 0x30008000 ...
Uncompressing Linux......................................................................Linux version 2.6.14 ([email protected]) (gcc version 3.4.1) #12 Sun Jan 14 13:16:14 EST 27CPU: ARM920Tid(wb) [41129200] revision 0 (ARMv4T)
Machine: SMDK2410
ATAG_INITRD is deprecated; please update your bootloader.
Memory policy: ECC disabled, Data cache writeback
CPU S3C2410A (id 0x32410002)
S3C2410: core 202.800 MHz, memory 101.400 MHz, peripheral 50.700 MHz
S3C2410 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
Kernel command line: "console=ttySAC0 initrd=0x30800000,0x2b308e root=/dev/ram init=/lin"irq: clearing pending ext status 00000800
irq: clearing <script src="http://pagead2.googlesyndication.com/pagead/show_ads.js" type="text/javascript"></script> subpending status 00000002
PID hash table entries: 512 (order: 9, 8192 bytes)
timer tcon=00500000, tcnt a509, tcfg 00000200,00000000, usec 00001e4c
Console: colour dummy device 80x30
Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)
Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)
Memory: 64MB = 64MB total
Memory: 59292KB available (2090K code, 462K data, 112K init)
Mount-cache hash table entries: 512
CPU: Testing write buffer coherency: ok
checking if image is initramfs...it isn't (no cpio magic); looks like an initrd
softlockup thread 0 started up.
Freeing initrd memory: 2764K
NET: Registered protocol family 16
USB Control, (c) 2006 sbc2410
S3C2410: Initialising architecture
SCSI subsystem initialized
usbcore: registered new driver usbfs
usbcore: registered new driver hub
NetWinder Floating Point Emulator V0.97 (double precision)
devfs: 2004-01-31 Richard Gooch ([email protected])
devfs: devfs_debug: 0x0
devfs: boot_options: 0x1
Initializing Cryptographic API
s3c2410-lcd s3c2410-lcd: no platform data for lcd, cannot attach
s3c2410-lcd: probe of s3c2410-lcd failed with error -22
Console: switching to colour frame buffer device 80x25
fb0: Virtual frame buffer device, using 1024K of video memory
S3C2410 RTC, (c) 2004 Simtec Electronics
s3c2410_serial0 at MMIO 0x50000000 (irq = 70) is a S3C2410
s3c2410_serial1 at MMIO 0x50004000 (irq = 73) is a S3C2410
s3c2410_serial2 at MMIO 0x50008000 (irq = 76) is a S3C2410
io scheduler noop registered
io scheduler anticipatory registered
io scheduler deadline registered
io scheduler cfq registered
RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize
loop: loaded (max 8 devices)
nbd: registered device at major 43
usbcore: registered new driver ub
Cirrus Logic CS8900A driver for Linux (Modified for SMDK2410)
pSMDK2410_ETH_IO=0x11000000,vSMDK2410_ETH_IO=0xe0000000
eth0: CS8900A rev E at 0xe0000300 irq=52, no eeprom , addr: 08: 0:3E:26:0A:5B
NFTL driver: nftlcore.c $Revision: 1.97 $, nftlmount.c $Revision: 1.40 $
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: Product: S3C24XX OHCI
usb usb1: Manufacturer: Linux 2.6.14 ohci_hcd
usb usb1: SerialNumber: s3c24xx
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 2 ports detected
Initializing USB Mass Storage driver...
usbcore: registered new driver usb-storage
USB Mass Storage support registered.
mice: PS/2 mouse device common for all mice
NET: Registered protocol family 2
IP route cache hash table entries: 1024 (order: 0, 4096 bytes)
TCP established hash table entries: 4096 (order: 2, 16384 bytes)
TCP bind hash table entries: 4096 (order: 2, 16384 bytes)
TCP: Hash tables configured (established 4096 bind 4096)
TCP reno registered
TCP bic registered
NET: Registered protocol family 1
RAMDISK: Compressed image found at block 0
RAMDISK: incomplete write (-28 != 32768) 4194304
RAMDISK: ran out of compressed data
invalid compressed format (err=1)
Root-NFS: No NFS server available, giving up.
VFS: Unable to mount root fs via NFS, trying floppy.
VFS: Cannot open root device "" or unknown-block(2,0)
Please append a correct "root=" boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)

出現上面情況，查閱資料才知道是因為沒有修改
Driver device  ->
  Block device ->
(4096)Default RAM disk size (kbytes)
改4096為8192

NET: Registered protocol family 1
RAMDISK: Compressed image found at block 0
VFS: Mounted root (ext2 filesystem).
Mounted devfs on /dev
                                                                                                 
Please press Enter to activate this console.
                                                                                                 
                                                                                                 
BusyBox v1.2.1 (2007.01.13-23:04+0000) Built-in shell (ash)
Enter 'help' for a list of built-in commands.
                                                                                                 
[[email protected] /]# ls
bin      etc      lib      mnt      sbin     usr
dev      hello    linuxrc  proc     tmp      var
[[email protected] /]# ./hello
hello,world
[[email protected] /]# ping www.baidu.com
ping: www.baidu.com: Unknown host
[[email protected] /]# ifconfig
[[email protected] /]# mount
devfs on /dev type devfs (rw)
/dev/root.old on / type ext2 (rw,nogrpid)
none on /dev type devfs (rw)
none on /proc type proc (rw,nodiratime)
devpts on /dev/pts type devpts (rw)
tmpfs on /dev/shm type tmpfs (rw)

這裡不知為何ping www.baidu.com 不通， 而
[[email protected] myuboot]# cd /public/today_ramfs/
[[email protected] today_ramfs]# ls
fs/  today.ramfs.gz
[[email protected] today_ramfs]# ls fs/
[[email protected] today_ramfs]# gunzip today.ramfs.gz
[[email protected] today_ramfs]# mount -o loop today.ramfs   fs/
[[email protected] today_ramfs]# cd fs
[[email protected] fs]# ls
bin/  dev/  etc/  hello*  lib/  [email protected]  mnt/  proc/  sbin/  tmp/  usr/  var/
[[email protected] fs]# ls lib
ld-2.3.2.so*        [email protected]                libpthread.so        [email protected]
[email protected]      [email protected]              [email protected]     [email protected]
libc-2.3.2.so*      libnss_dns-2.3.2.so*    libpthread.so_orig   libstdc++.so.6.0.1*
libcrypt-2.3.2.so*  [email protected]          libresolv-2.3.2.so*  libutil-2.3.2.so*
[email protected]        [email protected]        [email protected]        [email protected]
[email protected]      libnss_files-2.3.2.so*  [email protected]      [email protected]
libc.so             [email protected]        librt-2.3.2.so*      yaffs.o*
[email protected]          [email protected]      [email protected]
libm-2.3.2.so*      libpthread-0.10.so*     [email protected]
[[email protected] fs]# ls /public/myroot_nfs/lib/         這裡是NFS檔案系統的lib
ld-2.3.2.so*        [email protected]                libpthread.so        [email protected]
[email protected]      [email protected]              [email protected]     [email protected]
libc-2.3.2.so*      libnss_dns-2.3.2.so*    libpthread.so_orig   libstdc++.so.6.0.1*
libcrypt-2.3.2.so*  [email protected]          libresolv-2.3.2.so*  libutil-2.3.2.so*
[email protected]        [email protected]        [email protected]        [email protected]
[email protected]      libnss_files-2.3.2.so*  [email protected]      [email protected]
libc.so             [email protected]        librt-2.3.2.so*      yaffs.o*
[email protected]          libnss_files.so.[email protected]      [email protected]
libm-2.3.2.so*      libpthread-0.10.so*     [email protected]
[[email protected] fs]#

庫是一樣的，resolve.txt 中也指定了nameserver,為何不解析呢？

試了一下,telnet到板子也是可以的。ftp也可以。
[[email protected] /]# wget  ftp://59.69.74.87/hello.txt
Connecting to 59.69.74.87[59.69.74.87]:21
hello.txt            100% |*****************************|    21    --:--:-- ETA
[[email protected] /]#

我的問題是：
1： 用指令碼寫的linuxrc 也就是一句話 ,內容是
exec /sbin/init
和 用 busybox 生成的linuxrc 有何不同？

<script src="http://pagead2.googlesyndication.com/pagead/show_ads.js" type="text/javascript"></script>

2： 為何 ping www.baidu.com   不解析域名， 不要說我沒有加相應的庫哦？
剛剛試過NFSRoot時：
IP-Config: Complete:
     device=eth0, addr=59.69.74.199, mask=255.0.0.0, gw=59.69.74.1,
    host=matrix4, domain=, nis-domain=arm9.net,
    bootserver=59.69.74.87, rootserver=59.69.74.87, rootpath=
Looking up port of RPC 100003/2 on 59.69.74.87
Looking up port of RPC 100005/1 on 59.69.74.87
VFS: Mounted root (nfs filesystem).
Mounted devfs on /dev
Freeing init memory: 112K
                                                                                                 
Please press Enter to activate this console.
                                                                                                 
                                                                                                 
BusyBox v1.2.1 (2007.01.13-23:04+0000) Built-in shell (ash)
Enter 'help' for a list of built-in commands.
                                                                                                 
[[email protected] /]# ping www.baidu.com
PING www.a.shifen.com (211.94.144.100): 56 data bytes
                                                                                                 
--- www.a.shifen.com ping statistics ---
2 packets transmitted, 0 packets received, 100% packet loss