for lubuntu nand images, the boot parameters is stored at /dev/nandb.

root@cubieboard2:~# strings /dev/nandb
bootdelay=1
bootcmd=run setargs_nand boot_normal
console=ttyS0,115200
nand_root=/dev/system
mmc_root=/dev/mmcblk0p7
init=/init
loglevel=5
setargs_nand=setenv bootargs console=${console} init=${init} loglevel=${loglevel}
setargs_mmc=setenv bootargs console=${console} init=${init} loglevel=${loglevel}
boot_normal=boota 40007800
boot_recovery=sunxi_flash read 40007800 recovery;boota 40007800
boot_fastboot=fastboot
recovery_key_value_max=0x13
recovery_key_value_min=0x10
fastboot_key_value_max=0x8
fastboot_key_value_min=0x2

A way to change it is,

1. Dump the boot params to a file uEnv.txt
2. Change as you want
3. Convert uEnv.txt to a image with u_boot_env_gen tool (download)
4. dd back the image to /dev/nandb