/system and /data file system of Android

When I build the Android sources, I end up with 3 images. They are ramdisk.img, system.img and userdata.img. I'm trying to understand what these are made of and how they are used by Android. I came across articles which say "/system" is a yaffs2 file system. 1) If I want to make use of this开发者_如何学运维 on a real board, should the file system be yaffs2 or can it be any? 2) If I want to get the 3 images for another file system(say ext2), how do I do that?

You can modify the kernel to accept basically any filesystem you want (ext2 and ext4 are two examples), if you can make it compile. Then, it's just a matter of mounting and formatting the volume with the corresponding filesystem.

There are patches for different kernels in github and xda-developers. You will need to browse around to find the patch for your particular device. Unfortunately this is not something you can sole for all devices with a single hack.