我按照视频的步骤去做，弄完uboot就弄kernel，但是一直有问题，跟视频里面不同, 请问这是什么原因，SecureCRT显示如下
IP-Config: Complete:
device=eth0, addr=192.168.1.226, mask=255.255.255.0, gw=192.168.1.72,
host=smdk2440a, domain=, nis-domain=embedclub.com,
bootserver=192.168.1.72, rootserver=192.168.1.72, rootpath=
Looking up port of RPC 100003/2 on 192.168.1.72
eth0: link up, 100Mbps, full-duplex, lpa 0x4DE1
rpcbind: server 192.168.1.72 not responding, timed out
Root-NFS: Unable to get nfsd port number from server, using default
Looking up port of RPC 100005/1 on 192.168.1.72
rpcbind: server 192.168.1.72 not responding, timed out
Root-NFS: Unable to get mountd port number from server, using default
Root-NFS: Server returned error -5 while mounting /opt/rootfs
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 256 mtdblock0 (driver?)
1f01 128 mtdblock1 (driver?)
1f02 5120 mtdblock2 (driver?)
1f03 256640 mtdblock3 (driver?)
1f04 262144 mtdblock4 (driver?)
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)
Backtrace:
[<c00341cc>] (dump_backtrace+0x0/0x10c) from [<c03317d0>] (dump_stack+0x18/0x1c)
r7:c03e3ac8 r6:00008000 r5:c3923000 r4:c048a330
[<c03317b8>] (dump_stack+0x0/0x1c) from [<c0331820>] (panic+0x4c/0x114)
[<c03317d4>] (panic+0x0/0x114) from [<c0008dbc>] (mount_block_root+0x174/0x228)
r3:c38500ec r2:00000000 r1:c3823f60 r0:c03e3a60
[<c0008c48>] (mount_block_root+0x0/0x228) from [<c0008f34>] (mount_root+0xc4/0xfc)
[<c0008e70>] (mount_root+0x0/0xfc) from [<c0009094>] (prepare_namespace+0x128/0x180)
r5:c002081d r4:c0489d00
[<c0008f6c>] (prepare_namespace+0x0/0x180) from [<c00084b0>] (kernel_init+0xe0/0x114)
r5:c001f484 r4:c0489ac0
[<c00083d0>] (kernel_init+0x0/0x114) from [<c004bbbc>] (do_exit+0x0/0x620)
r5:00000000 r4:00000000
