Originally Posted by kitbor
What is the use of thiis mate pls explain and my phone is already rooted
You will be able to run scripts on boot which are called init.d scripts..they reside in /system/etc/init.d folder. After flashing this boot.img u will have to manually create init.d folder at aforesaid location using root explorer if u r already rooted OR root the device using popular SuperOneClick or UnlockRoot n then create the folder....
After that u need to install busybox to /system/xbin to run the scripts...
Download Busybox Installer by Jrummy OR Busybox Free by Stericson from Google Play Store and install busybox to xbin.
Now put some kickass scripts in init.d folder n go zoooommmm...
Examples of popular init.d scripts:
zipalign (zipaligns apk on boot so they load faster)
S97ramscript (ram management script)
99Supercharger (make the device faster)
Sdtweak (which increases sd card read cache memory)