如果使用NFS，內核需要重新配置。同時，server上的目錄中也必須要有必要的文件和目錄(NFS RAMDISK)。

Kernel configuration when using NFS ramdisk:
Below the details of the parameters when typing: make xconfig:
General setup:
-> Default kernel string : Erase its contents

Block Devices:
-> Network block device support : y
-> Ramdisk support: n 

File System:


-> Quota support: n
-> Kernel automounter support: y
-> DOS FAT fs support: y
-> VFAT (Windows 95) fs support: y
-> Journalling flash file system v2 (JFFS2) support: 0
-> /proc file system support: y
-> /dev file system support (EXP): y
-> Automatically mount a boot: y
-> Second extended fs support: y 

File System -> Network File systems:
-> NFS file system support : y
-> provide NFSv3 client support: y
-> root file system on NFS: y
-> NFS server support: n


redhat 9.0下面可以用redhat-config-nfs工具來配置。

Configure NFS client
This can be usefull to extend ramdisk capabilities and test new user applications. Applications can be cross-compiled on a distant linux box. The installation directory on the distant system can be seen by the AT91RM9200DK.
You need to rebuild the kernel and generate a new nfs dedicated uImage.
You need to mount the ramdisk , copy its contents under a dedicated directory where you can access them using nfs.

On the distant linux box modify the /etc/exports file to enable directory access: 

# Sample of /etc/exports file: 
# /usr/local/at91rm9200dk directory: it can be accessed by everybody with nobody's rights 
/usr/local/at91rm9200dk (ro, all_squash) 
Start the following demons: portmap, rpc.mountd and rpc.nfsd on the distant linux box. 
On the at91rm9200dk mount the distant file system: 

[root@AT91RM9200DK /root]$mkdir -p /mnt/linuxbox
[root@AT91RM9200DK /root]$mount -t nfs 10.159.245.144:/usr/local/at91rm9200dk /mnt/linuxbox


For NFS ramdisk
for a NFS mounting ramdisk you need to have a NFS server running from which the board's NFS client can fetch the ramdisk. First of all you have to make sure that there is a NFS server running on your PC (host) and second of all you have to edit a file called exports located in /etc and add the following entry : 
/usr/home/amine/RD/rd    root(rw,no_root_squash,insecure) 
Then you need to enter the following command :


[ root@host ] exportfs -r 
After all this you need to go back to your board and set some variables on U-Boot, it goes like this : 
 U-Boot > setenv bootargs root=/dev/nfs rw nfsroot=10.159.245.142:/usr/home/amine/RD/rd ip=10.159.245.180 console=ttyS4,115200 mem=32M 
 U-Boot > saveenv 
 U-Boot > tftp 21000000 AS/uImage 
 U-Boot > bootm 21000000 
In case you want to launch it automaticaly you can set a "bootcmd" variable, it goes like this :


 U-Boot > setenv bootcmd tftp 21000000 AS/uImage\; bootm 21000000 
 U-Boot > saveenv 
 U-Boot > run bootcmd