Root [HOW TO] Build kernel (zImage) into boot.img

[Rxpert83]

Hey Everyone!

I've gotten a few PM's from members trying to follow this guide and are S-ON about how to fastboot flash a kernel when it isn't packaged into a boot.img for you.


A good example of this is the arc reactor kernel:
[Kernel][JB][SENSE] Arc-Reactor [3.4.40][S2W][linaro] [-O3][WIP] - xda-developers

When you download and extract the kernel you'll notice there is no boot.img! However, the kernel is located inside of /kernel. The zImage is the output of the compiler when you build a kernel from source.

In order to flash that zImage, you'll need to incorporate it into the boot.img along with the proper ramdisk.


Step One: Download your files
Get the Android Image Kitchen:
[DEV][TOOL] Android Image Kitchen - Unpack/Repack Kernel/Recovery + ramdisk [Win32] - xda-developers

Arc Reactor Kernel (MikMik):
[Kernel][JB][SENSE] Arc-Reactor [3.4.40][S2W][linaro] [-O3][WIP] - theMikMik
Dev-Host:
Dev-Host - The Ultimate Free File Hosting / File Sharing Service

Stock boot.img for your ROM


Step 2: Extract the 2 zip files
Its also a good idea to place them somewhere convenient (I just do the desktop)

Step 3: Move the stock boot.img into the folder for the Android Image Kitchen

Step 4: Drag the boot.img onto unpackimg.bat
This unpackages the boot.img into the split_img and ramdisk folders.

Step 5:Inside of the split_img folder, youll see boot.img-zImage...remove or delete it from the folder.

Step 6: Place your zImage containing the arc reactor kernel (or whatever kernel you're using) into the folder. You may need to rename it to boot.img-zImage

Step 7: Go back one level to the android kitchen image folder, and click on the repackimg.bat file. This will rebuild your boot.img while incorporating the new zImage. Your boot image will be named image-new.img

You can now fastboot flash this using the command

fastboot flash boot image-new.img

just like before!

 

[ocnbrze]

Thanx rxpert.

So this is for s-on folks?

 

[Rxpert83]

Thanx rxpert.

So this is for s-on folks?

That particular example is, as the updater script from the kernels zip file can't decompile and recompile the boot.IMG on an s-on device. If the user is s-off they can flash that kernel as is.

Other than that, can be applicable to anyone wanting to decompile/recompile a boot.IMG to change things in the ramdisk or as the last step to compiling a kernel from source (compiling a kernel from source gives you the zImage, not the boot.img)

 

[ocnbrze]

That particular example is, as the updater script from the kernels zip file can't decompile and recompile the boot.IMG on an s-on device. If the user is s-off they can flash that kernel as is.

Other than that, can be applicable to anyone wanting to decompile/recompile a boot.IMG to change things in the ramdisk or as the last step to compiling a kernel from source (compiling a kernel from source gives you the zImage, not the boot.img)

ahhhh got it.....pretty cool

 

[Rush]

Pretty cool, Rx.

Now ...can you tell me why my Evo 4g lte just won't get s-off?

Anyway, I hope this tutorial will suffice many concerned questions.

 

[Rxpert83]

Pretty cool, Rx.

Now ...can you tell me why my Evo 4g lte just won't get s-off?

Anyway, I hope this tutorial will suffice many concerned questions.

That I can't answer. I havent been on the LTEvo in nearly a year and aren't aware of the nuances of s-off.

I just made a thread about a brand new S-OFF method. Perhaps that will work

 

[Rush]

That I can't answer. I havent been on the LTEvo in nearly a year and aren't aware of the nuances of s-off.

I just made a thread about a brand new S-OFF method. Perhaps that will work

I'm 85% certain that the problem with this phone not being able to get s-off is software-related.

Yeah, as for that new method of getting s-off — I'll try it out on Monday evening.

Thanks again.