Netboot have to be configured in uboot and relies on a remote TFTP/NFS server. The TFTP/NFS-Server provides the root filesystem with Kernel and DeviceTree and have to be configured accordingly.
On some DHCP servers (eg. common used Fritz-Box models) the serverip environment variable will be overwritten on dhcp command. To do a netboot on those networks, set "serverip" after the dhcp command again or use static IP address on module.
Example of manual netboot:
=> setenv nfsroot <YOUR_ROOTFS_ON_NETBOOT_SERVER> => run findfdt => setenv ip_dyn no => setenv autoload no => dhcp => setenv serverip <YOUR_NETBOOT_SERVER_IP> => run netboot
If netboot should be default boot, stop before “run netboot” command and do:
=> setenv bootcmd run netboot => savee => reset
Remark:
This will also save IP-Address and the used device tree to environment