[HOWTO] Re-flash stock kernel, after your device is rooted

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Hello everyone,

I saw this question over and over around so I decided to post a quick guide here.

After I installed the insecure kernel on my SGS2, to allow me to root, I did a series of quadrant tests. And after comparing 10 runs with the 10 runs I did prior to root, I ended up with the impression that I lost about 200-400 points per run. The tests were not entirely conclusive, since the margin is not big (compared with the total). Regardless, I still wanted to try to squeeze out every bit of performance I can out of this beast. That's when I decided to re-flash the original stock kernel.

What you will need, is basically the same thing you did to gain root, but with another kernel.

Make sure you know what you are doing. I am not responsible if you do it wrong and brick your phone.

1. First download the stock kernel:
You can find the stock kernels here: http://nma.usk.bz/sgs2.php

DO NOT UNTAR THE FILE. Leave it as it is.

2. Now open Odin and put your phone in Download mode
3. IMPORTANT: Make sure that "Auto Reboot" and "F.Reset Time" are check. And that EVERYTHING else is UNchecked.
4. Load the .tar file on the PDA field. Just click on "PDA" and open the file.
5. Click "Start"

Done, you are back to your stock kernel and will keep root. This does not revert what you already installed (su, SuperUser, busybox, etc).

If you have any questions, post it here.

UPDATES:
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- Added XWKE7 stock kernel (05/21/2011)

Hi uskr, I think this may be the same file in this top post in this thread which is what I just flashed to but thanks for this anyway.


http://forum.xda-developers.com/show...056334&page=35

Originally Posted by uskr

Hello everyone,

I saw this question over and over around so I decided to post a quick guide here.

After I installed the insecure kernel on my SGS2, to allow me to root, I did a series of quadrant tests. And after comparing 10 runs with the 10 runs I did prior to root, I ended up with the impression that I lost about 200-400 points per run. The tests were not entirely conclusive, since the margin is not big (compared with the total). Regardless, I still wanted to try to squeeze out every bit of performance I can out of this beast. That's when I decided to re-flash the original stock kernel.

What you will need, is basically the same thing you did to gain root, but with another kernel.

Make sure you know what you are doing. I am not responsible if you do it wrong and brick your phone.

1. First download the stock kernel: http://nma.usk.bz/files/I9100XWKDD_StockKernel.tar

DO NOT UNTAR THE FILE. Leave it as it is.

2. Now open Odin
3. IMPORTANT: Make sure that "Auto Reboot" and "F.Reset Time" are check. And that EVERYTHING else is UNchecked.
4. Load the I9100XWKDD_StockKernel.tar file on the PDA field. Just click on "PDA" and open the file.
5. Click "Start"

Done, you are back to your stock kernel and will keep root. This does not revert what you already installed (su, SuperUser, busybox, etc).

If you have any questions, post it here.

Thank you for pointing it out. I had a hard time finding it when I needed. Hope this helps more people out there.

This one is from the original stock rom downloaded from kies. I just extracted the zImage.

I no this is not relevant To stock kernel but if i update my phone to newest firmware this will work the same way,?
also there is a overclock kernel out if i want overclock kernel after i update to new firmware i would need to flash the root kernel then flash the overclock kernel to beable to have my phone run newest firmware with overclock kernel that is rooted.?
Thanks
Sent from my GT-I9100 using XDA App

When we update to XWKE1, flash the unsecure KDD Kernel, root, how do we get back to KE1 Kernel?

Can you point on how to extract it?

Originally Posted by walda

When we update to XWKE1, flash the unsecure KDD Kernel, root, how do we get back to KE1 Kernel?

Can you point on how to extract it?

+1
How can we extract only the kernel from a stock firmware?

I googled a lot and figgured out that this way should be the right.

* Flash new Firmware via ODIN (.tar File)
* Root with old KDD Kernel
* Open the FW .tar File
* Delete all except "zImage"
* Flash new .tar file via Odin

That should it be. Am not sure but

Will try when i got 100% and backuped my sdcard

So we have to delete all the files in the tar, except "zImage". I found a guide to do it, but for the *.rar, I tried with the *.tar but it didn't work
http://xona.com/2006/07/05c.html

Thanks. The kernel I used to root I think introduced an intermittent mic issue during calls.. now I'm back to the standard kernel and no more issue.

Thanks dude