1、配置网络部分，主要是使能CONFIG_IP_PNP以在2中能够看到Root file system on NFS选项
Networking support 
	Networking options 
		TCP/IP networking
				IP: kernel level autoconfiguration
					[*] IP: DHCP support
					[*] IP: BOOTP support
					
2、配置开启nfs服务
File systems  --->	
	Network File Systems  --->
		<*> NFS client support 
		[*] NFS client support for NFS version 3                                  [*] NFS client support for the NFSv3 ACL protocol extension 
		[*] NFS client support for NFS version 4 (EXPERIMENTAL) 
		[*] NFS client support for NFSv4.1 (DEVELOPER ONLY) 
		[*] Root file system on NFS  
					
3、在uboot中设置如下启动参数（IP根据实际使用更改）
setenv bootargs root=/dev/nfs nfsroot=192.168.1.141:/root/porting_x210/rootfs ip=192.168.1.10:192.168.1.141:192.168.1.1:255.255.255.0::eth0:off  init=/linuxrc console=ttySAC2,115200