今晚遇到一个很奇怪的问题，TQ2440开发板的nfs系统突然启动不了了，前几天一直都是这么用，一直没有发生过今晚那么特殊的情况，下面是开发板的启动信息。
Root-NFS: Unable to get nfsd port number from server, using default
Looking up port of RPC 100005/1 on 192.168.0.105
rpcbind: server 192.168.0.105 not responding, timed out
Root-NFS: Unable to get mountd port number from server, using default
Root-NFS: Server returned error -5 while mounting /usr/src/root_2.6.30.4
VFS: Unable to mount root fs via NFS, trying floppy.
VFS: Cannot open root device "nfs" or unknown-block(2,0)
Please append a correct "root=" boot option; here are the available partitions:
1f00 261888 mtdblock0 (driver?)
1f01 3072 mtdblock1 (driver?)
1f02 257024 mtdblock2 (driver?)
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)
[<c002f3f4>] (unwind_backtrace+0x0/0xdc) from [<c0290ffc>] (panic+0x40/0x110)
[<c0290ffc>] (panic+0x40/0x110) from [<c0008fcc>] (mount_block_root+0x1d0/0x210)
[<c0008fcc>] (mount_block_root+0x1d0/0x210) from [<c0009264>] (prepare_namespace+0x164/0x1bc)
[<c0009264>] (prepare_namespace+0x164/0x1bc) from [<c0008598>] (kernel_init+0xb4/0xe0)
[<c0008598>] (kernel_init+0xb4/0xe0) from [<c0041cd8>] (do_exit+0x0/0x578)
[<c0041cd8>] (do_exit+0x0/0x578) from [<00000001>] (0x1)
很明显，它说我的nfs服务器不正常，但是事实我的nfs并没有不正常，一般遇到这种情况就是要么网络ping不通，要么是nfs没有正常启动。但是我正确设置了虚拟机的IP之后，且多次重启nfs /etc/init.d/nfs restart 。依旧不能解决这个问题，后来问了一个师兄，他说，用网线直接连接开发板与电脑，我按照他说的这么做，真的就可以了。而且连接上网络后，将网线重新各自接回路由，等待一段时间后，居然可以使用nfs了。
至今不明白为什么突然我的nfs突然就启动不成功了，u-boot的启动参数也没有改，也是跟前几天一样：
bootargs=console=ttySAC0 root=/dev/nfs nfsroot=192.168.0.105:/usr/src/root_2.6.30.4 ip=192.168.0.5:192.168.0.105:192.168.0.5:255.255.255.0:SKY2440.embedsky.net:eth0:off
如果有哪位朋友知道为什么，如何解决这个问题，麻烦请告诉我，感激不尽
。