[guang6321]

Thanks for your suggestions.
Try to answer your questions:

ISO9660 support:
All source codes are on the online file server, You have to rebuild kernel to support ISO9660 filesystem.

Chinese hieroglyphs:
There is no Chinese mode in Onboard, it is IBUS input method, which is used to input Chinese style characters. To switch between Chinese and English mode press "CTRL+SPACE" keys. I think IBUS is not used to switch between some latin layouts, so you may need to try other ways.
The custom onboard source codes can be found on the online file server.(file:custom.tar.gz)


About Backups:
All Debian necessary files are in mmc partition 6, I'll give you an explanation of how to make a whole backup

16GB MMC partitions table:
** head: 30MiB(RAW)
** part1: 4096MiB /FAT32 (Books)
** part2: 1536MiB(Android Data)
** part3: 512MIB(Android System)
** part4: extension
**** part5: 64MiB/FAT32
**** part6: 8192MiB (Linux Rootfs)
**** part7: 512MiB (Linux swap)


** The first 30MiB head contains partiton table(first 1KB),uboot cmdline and something important, use "dd cmd" to make backups(skip first 1KB)
** part1 contains books, user fonts, dictionaries, backup these
** part2, part3 are for android, not used in Debian
** part4, extension
**** part5: kernel uImage files, boot config files, backup these
**** part6: Debian rootfs, backup these
**** part7: Linux swap partition

Part5 is fat32 format, and the sequence number(mmcblk1p5) is directly written in uboot, not configurable;
Part1 and Part7 are mounted in Debian;
Part6 sequence number(mmcblk1p6) is written in uboot cmdline area(extenal mmc:768KB ~ 768KB+128KB), so is configurable;