偶nfs挂载老不成功，下面是提示，请问是什么原因？在这里多谢了！
IP-Config: Complete:
device=eth0, addr=172.16.24.244, mask=255.255.255.0, gw=172.16.24.200,
host=www, domain=, nis-domain=yctek.com,
bootserver=172.16.24.228, rootserver=172.16.24.228, rootpath=
Looking up port of RPC 100003/2 on 172.16.24.228
portmap: server 172.16.24.228 not responding, timed out
Root-NFS: Unable to get nfsd port number from server, using default
Looking up port of RPC 100005/1 on 172.16.24.228
portmap: server 172.16.24.228 not responding, timed out
Root-NFS: Unable to get mountd port number from server, using default
Root-NFS: Server returned error -5 while mounting /utuLinux/s3c2440/s3c2440_recover
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
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)
