Use Uboot to boot the kernel and mount the NFS root file system

After configuring the kernel, copy the generated kernel file uimage to/tftpboot/, download the kernel to the board via the TFTP server, and use the command: TFTP 31000000 uimage. Configure the Bootargs environment variable after the download is complete: setenv Bootargs noinitrd console=ttysac0,115200 init=/init root=/dev/nfs rw nfsroot=192.168.1.118:/home/rootfs,proto=tcp, Nfsvers=3 Ip=192.168.1.119:192.168.1.118:192.168.1.1:255.255.255.0::eth0:off
Because the UDP protocol is used by default when mounting NFS file systems, dm9000 frequently drops packets (with a packet drop rate greater than 50%) and changes the network protocol to TCP to resolve the problem.

Run Bootm 31000000 to boot the kernel and mount the NFS system after configuring the startup parameters.
But burn the kernel file to NAND Flash and configure the Bootcmd command: setenv bootcmd NAND write 31000000 300000 300000\;bootm 31000000

Reboot the board to discover that the kernel started successfully but mounted the root file system failed:

The error message indicates that the network card could not be found, and the experiment found that if the TFTP command was run before the BOOTM command, the system could mount successfully and BOOTM would not succeed if the TFTP command was not running. Online search found that the Development Board running in the Uboot state only use network commands to enable the NIC, so the problem may be that the kernel corresponding to the network card driver does not enable the network card caused.

Use Uboot to boot the kernel and mount the NFS root file system