Installing u-boot.imx-nand to imx6ull NAND boot partition failed to set up for ubootenv

[nobody93]

Hi,
I have u-boot and u-boot environment in MTD partitions in imx6ull NAND:
0: boot 0x00400000 0x00000000 0
1: ubootenv 0x00100000 0x00400000 0

I used the kob tool to install u-boot.imx-nand to iMX6ULL MTD partition 0 boot, but what is the mechanism to install bootargs and bootcmd which are defined in u-boot.imx-nand to ubootenv MTD partition?

I failed NAND boot because it missed the both bootcmd and bootargs in u-boot env:
=> print
baudrate=115200
board_name=ULZ-EVK
board_rev=14X14
bootdelay=3
bootsys=1
fdtcontroladdr=9ee17918
loadaddr=0x80800000
stderr=serial
stdin=serial
stdout=serial
tee=no
usb_net_cmd=usb start

Should I use fw_setenv to set bootcmd and bootargs to my ubootenv MTD partition after installing the u-boot.imx-nand to boot partition?

What I am missing here?

Many blogs advised not to use setenv or fw_setenv, but to get boot variables from the u-boot, but how?

Thank you.