Some manufacturers pack their ROMs into an nb0 file, which consists of a number of partitions in img format. In order to get to these img files, we first need to learn how to unpack an nb0 file, then, of course, how to repack the nb0. 

You will need:

The Java Runtime Environment (if you're developing, you should have this and JDK anyway)

A688 Tools - Download them here   

Method to Unpack nb0 files

1. Extract A688 tools to a memorable location

( NOTE - nb0-utils.jar will be referred to - you can find it in your A688_Tools folder, in the subdirectory /RomUnpackTools_Win)

2. Place the nb0 file in /A688_Tools/RomUnpackTools_win

3. Open a command prompt, and CD (change directory) to the A688_Tools/RomUnpackTools_win directory

4. Use the following command to unpack the NB0 file which you want to unpack:

java -jar nb0-utils.jar unpack file-to-unpack.nb0 folder-to-unpack-to

Of course, rename the file to unpack and folder to unpack to sections to suit. 

If you get following message, you need add "-Xmx512M" in your command:

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space

java -Xmx512M -jar nb0-utils.jar unpack file-to-unpack.nb0 folder-to-unpack-to

To edit the extracted contents, see our guide on loop mounting img files.

Method to Re-pack nb0 files

1. Open a command prompt, and CD to the A688_Tools/RomUnpackTools_win directory

2. Use the following command to repack target directory into a NB0 file.

java -jar nb0-utils.jar pack name-of-output-file.nb0 folder-to-pack-from

Of course, rename the name-of-output-file and folder-to-pack-from to suit.

That's it! All done!