内核不能挂载文件系统

照linux移植手册做到step 1,1，构建文件系统，内核不能挂载文件系统，错误信息如下:
drivers/rtc/hctosys.c: unable to open rtc device (rtc0)
Root-NFS: No NFS server available, giving up.
VFS: Unable to mount root fs via NFS, trying floppy.
VFS: Cannot open root device "mtdblock2" or unknown-block(2,0)
Please append a correct "root=" boot option; here are the available partitions:
1f00          262144 mtdblock0 (driver?)
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)
Backtrace:
[<c002cfd4>] (dump_backtrace+0x0/0x10c) from [<c02b5e78>] (dump_stack+0x18/0x1c)
r7:c38090db r6:c03c0680 r5:c3809000 r4:c381df40
[<c02b5e60>] (dump_stack+0x0/0x1c) from [<c02b5ec8>] (panic+0x4c/0x124)
[<c02b5e7c>] (panic+0x0/0x124) from [<c0008e8c>] (mount_block_root+0x178/0x234)
r3:00000000 r2:c386092c r1:c381df40 r0:c03406b4
[<c0008d14>] (mount_block_root+0x0/0x234) from [<c0008ff8>] (mount_root+0xb0/0xf4)
[<c0008f48>] (mount_root+0x0/0xf4) from [<c0009140>] (prepare_namespace+0x104/0x198)
r7:00000000 r6:c002283c r5:c002283c r4:c03c0044
[<c000903c>] (prepare_namespace+0x0/0x198) from [<c0008478>] (kernel_init+0xc8/0xf4)
r6:c0021644 r5:c00212d4 r4:c0021644
[<c00083b0>] (kernel_init+0x0/0xf4) from [<c003e01c>] (do_exit+0x0/0x620)
r7:00000000 r6:00000000 r5:00000000 r4:00000000
在网上找了很多方法都没解决，请版主帮忙指导

请看
\TQ2440_CD\TQ2440开发板配套教材集、天嵌科技出品-Linux移植之Step By Step_V4.5_20100605.pdf手册第170页