Init.d has a special place in Android. With it, users can install scripts and mods to run at boot, and thus modify almost any aspect of the phone that they want. There are battery tweaks, performance tweaks, GPS tweaks, signal tweaks, and the list goes on and on. However for these scripts to work, the phone must first have init.d support. Typically, Ramdisks provide init.d support, but sometimes it is possible to gain init.d support without flashing a new Ramdisk, or even without altering the Ramdisk at all.
This is something that XDA Recognized Developer smokin1337 has been working on for a number of devices. With a mod called EZ InitD, smokin1337 looks to help users add init.d support easily. Additionally, the developer gives a couple of options on how to use the mod. One version is for users to flash via custom recovery, while the other is for ROM developers to include in their ROMs. The best part is, it’s simple.
After the mod is applied, anything in your init.d folder will run on boot, as it normally would. In the ROM developer version, developers can actually change the directory to whatever they want. In other words, there could be ROMs made with init.d support but without an actual init.d folder. (Ed: I’m thinking /etc/NyanCat or /etc/bacolicious, myself.) The method has been tested on the HTC One S and the HTC One X, but it should actually work on any device. As many users will tell you, init.d support comes from the Ramdisk. This is not necessarily true. According to smokin1337:
This mod will add init.d support to any rom even stock roms without editing the ramdisk. Instead it uses the post_boot.sh file that is in most if not all roms. It should work on most devices, if it does not work on yours please look in /system/etc and post the name of the file that contains “post_boot.sh”.
So, given this method, it’s actually possible to gain init.d support without switching, editing or otherwise touching the Ramdisk or kernel. For additional information, check out the original thread._________