thank you my friend, but i tried before your answer to check the answer from this command under telnet;
cat /proc/mtd
and i obtain this answer from my vu+duo;
root@bm750:~# cat /proc/mtd
dev: size erasesize name
mtd0: 07600000 00020000 "rootfs"
mtd1: 00400000 00020000 "kernel"
mtd2: 00200000 00020000 "boot"
mtd3: 00100000 00020000 "cfe"
mtd4: 00080000 00020000 "mac"
mtd5: 00080000 00020000 "env"
mtd6: 00100000 00020000 "nvm"
root@bm750:~#
i already try various source for the bootloader(duo_cfe_3_0_usb).
and i got always the same answer, i thought that i should see for
mtd2: 00400000 00020000 "boot"
so i don't know what to do
thank you