[Android Software/Hacking General [Developers Only]] fun_:
here is an example for rkafpack

$ rkunpack N3NET-2.3-20110722.img
[COLOR="Red"][B]FIRMWARE_VER:1.0.0[/B][/COLOR]
[COLOR="Red"][B]MACHINE_MODEL:rk2818sdk[/B][/COLOR]
MACHINE_ID:
[COLOR="Red"][B]MANUFACTURER:rock-chips[/B][/COLOR]

unpacking 12 files
-------------------------------------------------------------------------------
00000800-00000fff [COLOR="Red"][B]HWDEF:HWDEF[/B][/COLOR] 797 bytes
00001000-000017ff [COLOR="Red"][B]package-file:package-file[/B][/COLOR] 532 bytes
00001800-00021fff [COLOR="Red"][B]bootloader:RK28xxLoader(L).bin[/B][/COLOR] 131700 bytes
00022000-000227ff [COLOR="Red"][B]parameter:parameter:0x0@0x0[/B][/COLOR] 506 bytes
00022800-0002e7ff [COLOR="Red"][B]misc:Image/misc.img:0x0@0x2000[/B][/COLOR] 49152 bytes
0002e800-0066bfff [COLOR="Red"][B]kernel:Image/kernel.img:0x0@0x4000[/B][/COLOR] 6541946 bytes
0066c000-006947ff [COLOR="Red"][B]boot:Image/boot.img:0x0@0x8000[/B][/COLOR] 163844 bytes
00694800-008e8fff [COLOR="Red"][B]recovery:Image/recovery.img:0x0@0xa000[/B][/COLOR] 2441220 bytes
008e9000-085fc7ff [COLOR="Red"][B]system:Image/system.img:0x0@0xe000[/B][/COLOR] 131149828 bytes
----------------- [COLOR="Red"][B]backup:SELF:0x0@0x52000[/B][/COLOR] (N3NET-2.3-20110722.img) 140498948 bytes
085fc800-085fcfff [COLOR="Red"][COLOR="Red"][B]update-script:update-script[/B][/COLOR][/COLOR] 1294 bytes
085fd000-085fd7ff [COLOR="Red"][B]recover-script:recover-script[/B][/COLOR] 266 bytes
-------------------------------------------------------------------------------
unpacked
$ rkafpack \
[COLOR="Red"][B]FIRMWARE_VER:1.0.0[/B][/COLOR] \
[COLOR="Red"][B]MACHINE_MODEL:rk2818sdk[/B][/COLOR] \
[COLOR="Red"][B]MANUFACTURER:rock-chips[/B][/COLOR] \
[COLOR="Red"][B]HWDEF:HWDEF[/B][/COLOR] \
[COLOR="Red"][B]package-file:package-file[/B][/COLOR] \
'[COLOR="Red"][B]bootloader:RK28xxLoader(L).bin[/B][/COLOR]' \
[COLOR="Red"][B]parameter:parameter:0x0@0x0[/B][/COLOR] \
[COLOR="Red"][B]misc:Image/misc.img:0x0@0x2000[/B][/COLOR] \
[COLOR="Red"][B][B]kernel:Image/kernel.img:0x0@0x4000[/B][/B][/COLOR] \
[COLOR="Red"][B]boot:Image/boot.img:0x0@0x8000[/B][/COLOR] \
[COLOR="Red"][B]recovery:Image/recovery.img:0x0@0xa000[/B][/COLOR] \
[COLOR="Red"][B]system:Image/system.img:0x0@0xe000[/B][/COLOR] \
[COLOR="Red"][B]backup:SELF:0x0@0x52000[/B][/COLOR] \
[COLOR="Red"][B]update-script:update-script[/B][/COLOR] \
[COLOR="Red"][B]recover-script:recover-script[/B][/COLOR] \
> new.img
$ sha1sum N3NET-2.3-20110722.img new.img
e758a6c47dca7f09f0b8a82ad89b0cd7c7c8e826 N3NET-2.3-20110722.img
e758a6c47dca7f09f0b8a82ad89b0cd7c7c8e826 new.img

some values are empty in RK2818 ROM.

--

here is how to make RKFW image

$ rkunpack N50-2.3-20111103-ZZ-SDK2.0.img
VERSION:2.0.3

unpacking
00000000-00000065 N50-2.3-20111103-ZZ-SDK2.0.img-HEAD 102 bytes
00000066-00022623 N50-2.3-20111103-ZZ-SDK2.0.img-BOOT 140734 bytes
00022624-0c342627 update.img 204603396 bytes

unpacking update.img
================================================================================
FIRMWARE_VER:0.2.3
MACHINE_MODEL:rk29sdk
MACHINE_ID:007
MANUFACTURER:RK29SDK

unpacking 10 files
-------------------------------------------------------------------------------
00000800-00000fff package-file:package-file 540 bytes
00001000-000237ff bootloader:RK29xxLoader(L)_V2.08.bin 140734 bytes
00023800-00023fff parameter:parameter:0x2000@0x0 610 bytes
00024000-0002ffff misc:Image/misc.img:0x2000@0x2000 49152 bytes
00030000-006a3fff boot:Image/boot.img:0x8000@0x8000 6766592 bytes
006a4000-01167fff recovery:Image/recovery.img:0x8000@0x10000 11288576 bytes
01168000-0c31efff system:Image/system.img:0x80000@0x1cc000 186346496 bytes
----------------- backup:SELF:0x78000@0x18000 (update.img) 204603396 bytes
0c31f000-0c31f7ff update-script:update-script 933 bytes
0c31f800-0c31ffff recover-script:recover-script 266 bytes
-------------------------------------------------------------------------------
================================================================================

00022624-0c342627 N50-2.3-20111103-ZZ-SDK2.0.img-MD5 32 bytes
unpacked
$ cat N50-2.3-20111103-ZZ-SDK2.0.img-HEAD N50-2.3-20111103-ZZ-SDK2.0.img-BOOT update.img > new.img
$ md5sum new.img
[COLOR="Red"][B]5191abc65649eacf8d2476e37d84a046[/B][/COLOR] new.img
$ cat N50-2.3-20111103-ZZ-SDK2.0.img-MD5
5191abc65649eacf8d2476e37d84a046
$ echo -n [COLOR="Red"][B]5191abc65649eacf8d2476e37d84a046[/B][/COLOR] >> new.img
$ sha1sum N50-2.3-20111103-ZZ-SDK2.0.img new.img
3120b13df8886e0ddfae0e35379443c27c925572 N50-2.3-20111103-ZZ-SDK2.0.img
3120b13df8886e0ddfae0e35379443c27c925572 new.img