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[Q] What's the deal with kernels?

Since I was an android virgin until just before Christmas, I'm still trying to get to grips with all the cool stuff that can be done.
I've rooted the phone and unlocked the bootloader. Everything else is currently stock.
I don't want to go to Clockwork recovery, or Cyanogen/MoDaCo ROMs. Not yet. I'm still savouring the "Google Experience".
However, I have three questions (which may turn into many more ) about flashing new kernels, and I don't want to clog up any specific kernal thread with noob questions.
1) Does flashing a kernel wipe the whole phone the way unlocking the bootloader did?
2) If you're running stock ROM with new kernel, will you still pick up OTA updates as before?
3) How do you get the original kernal back if you don't like the new one (or if it just goes totally tits up)?
Thanks guys
EDIT: Yes, I realise there is a search and this may well have been asked before. But before someone points this out, I'd like to mention that if you do a search for "android kernel", you get approximately 1 bajillion hits...

Mr.Clark said:
Since I was an android virgin until just before Christmas, I'm still trying to get to grips with all the cool stuff that can be done.
I've rooted the phone and unlocked the bootloader. Everything else is currently stock.
I don't want to go to Clockwork recovery, or Cyanogen/MoDaCo ROMs. Not yet. I'm still savouring the "Google Experience".
However, I have three questions (which may turn into many more ) about flashing new kernels, and I don't want to clog up any specific kernal thread with noob questions.
1) Does flashing a kernel wipe the whole phone the way unlocking the bootloader did?
2) If you're running stock ROM with new kernel, will you still pick up OTA updates as before?
3) How do you get the original kernal back if you don't like the new one (or if it just goes totally tits up)?
Thanks guys
EDIT: Yes, I realise there is a search and this may well have been asked before. But before someone points this out, I'd like to mention that if you do a search for "android kernel", you get approximately 1 bajillion hits...
Click to expand...
Click to collapse
1) No, you should not wipe anything before flashing a kernel. You should however do a NANDroid backup.
2) You should be able to but it will wipe your kernel.
3) Restore your backup from #1

Mr.Clark said:
Since I was an android virgin until just before Christmas, I'm still trying to get to grips with all the cool stuff that can be done.
I've rooted the phone and unlocked the bootloader. Everything else is currently stock.
I don't want to go to Clockwork recovery, or Cyanogen/MoDaCo ROMs. Not yet. I'm still savouring the "Google Experience".
However, I have three questions (which may turn into many more ) about flashing new kernels, and I don't want to clog up any specific kernal thread with noob questions.
1) Does flashing a kernel wipe the whole phone the way unlocking the bootloader did?
2) If you're running stock ROM with new kernel, will you still pick up OTA updates as before?
3) How do you get the original kernal back if you don't like the new one (or if it just goes totally tits up)?
Thanks guys
EDIT: Yes, I realise there is a search and this may well have been asked before. But before someone points this out, I'd like to mention that if you do a search for "android kernel", you get approximately 1 bajillion hits...
Click to expand...
Click to collapse
flashing a kernel doesnt wipe your phone, it simply replaces whatever kernel is in your phone at the moment.

kenvan19 said:
1) No, you should not wipe anything before flashing a kernel. You should however do a NANDroid backup.
Click to expand...
Click to collapse
Right. Guess what my next question will be
kenvan19 said:
2) You should be able to but it will wipe your kernel.
3) Restore your backup from #1
Click to expand...
Click to collapse
2) Is fine, as once I've figured out how to NANDroid backup, re-flashing it should be easy enough. 3) Is fine, once I've taken the backup in the first place.
simms22 said:
flashing a kernel doesnt wipe your phone, it simply replaces whatever kernel is in your phone at the moment.
Click to expand...
Click to collapse
Excellent, thanks!
Ok. So all the NANDroid guides I've seen here start with ADB and Fastboot (which I remember doing when I rooted the phone), but then they say about flashing alternative recovery images... is that necessary? Or is that what the fastboot thing was?
I've just checked and ADB still works, so if fastboot is an alternative recovery image, am I good to take a NANDroid backup, and if so, how do I do that?
If Fastboot is not an appropriate recovery image, do I need Clockwork Recovery (is that different to the "CWM" I see mentioned around here?)?
The Nexus S guide I read said that there was a NANDroid option in the Clockwork Recovery. Now this isn't in my recovery options, obviously, but I assume with ADB, a command prompt and a few instructions, I can do it manually. Maybe.
Bear with me guys, I'll get there eventually...

Ok, scratch the NANDroid questions. NANDroid is a backup tool contained in the Clockwork Mod recovery image.
Using Fastboot, you can boot from the recovery image without flashing it (using this guide here), so I've still got whatever recovery image I got when I did Paul's rooting technique, but have booted into CWM once to do the NANDroid backup.
I may flash CWM later, that's a task for another day.
So. Now I've got the backup (and thus, booting from that image again later, the ability to restore from it), I can try flashing the kernel. Which I can do from the regular recovery image.

Mr.Clark said:
Ok, scratch the NANDroid questions. NANDroid is a backup tool contained in the Clockwork Mod recovery image.
Using Fastboot, you can boot from the recovery image without flashing it (using this guide here), so I've still got whatever recovery image I got when I did Paul's rooting technique, but have booted into CWM once to do the NANDroid backup.
I may flash CWM later, that's a task for another day.
So. Now I've got the backup (and thus, booting from that image again later, the ability to restore from it), I can try flashing the kernel. Which I can do from the regular recovery image.
Click to expand...
Click to collapse
To flash from the stock recovery you must rename files update.zip just FYI. I've said it before and I'll say it again; there are no possible negative repercussions from flashing a non-stock recovery image.

Apparently it was unsigned, so the stock recovery wouldn't do anything with it.
Back in CWM and it worked fine. I may have to flash that, it's damned useful...
So now I have a new kernel!
Thanks for all your help

Mr.Clark said:
Apparently it was unsigned, so the stock recovery wouldn't do anything with it.
Back in CWM and it worked fine. I may have to flash that, it's damned useful...
So now I have a new kernel!
Thanks for all your help
Click to expand...
Click to collapse
It is very useful indeed! Enjoy your kernel

Ah, am I right in thinking that if I flash CWM, I can't revert back to stock if I want to?
I'm hoping to do nothing permanent at this point...

Mr.Clark said:
Ah, am I right in thinking that if I flash CWM, I can't revert back to stock if I want to?
I'm hoping to do nothing permanent at this point...
Click to expand...
Click to collapse
Yes, you can flash back. Not only can you but depending on how you did flash the recovery the phone may revert it on your behalf. I know mine has several times, like any time I reboot. There's ways to stop it from doing that but I don't mind.
To get the stock recovery back if it isn't automatically restoring means flashing an NAND from the Dev section here.

I didn't want to open a new thread just to ask this so I hope it's OK to post it here.
I'm very interested in getting supercurio's voodoo sound and ext4 mod on my Nexus S but I don't need/want the overclocked frequencies and other stuff included on most of the kernels out there. You guys know any kernel that I could flash to get those and keep my stock fequencies?
Thanks
Sent from my Nexus S using XDA App

nicholasbgr said:
I didn't want to open a new thread just to ask this so I hope it's OK to post it here.
I'm very interested in getting supercurio's voodoo sound and ext4 mod on my Nexus S but I don't need/want the overclocked frequencies and other stuff included on most of the kernels out there. You guys know any kernel that I could flash to get those and keep my stock fequencies?
Thanks
Sent from my Nexus S using XDA App
Click to expand...
Click to collapse
I use overclocked with voodoo and setcpu...you can keep it set to 1000 and not over the stock limit.

Bionix 1.3 is solid and no OC
Sent from my Nexus S using XDA App

nicholasbgr said:
I didn't want to open a new thread just to ask this so I hope it's OK to post it here.
I'm very interested in getting supercurio's voodoo sound and ext4 mod on my Nexus S but I don't need/want the overclocked frequencies and other stuff included on most of the kernels out there. You guys know any kernel that I could flash to get those and keep my stock fequencies?
Thanks
Sent from my Nexus S using XDA App
Click to expand...
Click to collapse
If you flash the Trinity max kernel and do not adjust the clock you will have everything your asking for. This kernel boots at stock and has Voodoo and ext4 built in.

icandy75 said:
If you flash the Trinity max kernel and do not adjust the clock you will have everything your asking for. This kernel boots at stock and has Voodoo and ext4 built in.
Click to expand...
Click to collapse
So your saying the trinity max kernel has voodoo built in?
Sent from my bionix nexus s

mrnexus said:
So your saying the trinity max kernel has voodoo built in?
Sent from my bionix nexus s
Click to expand...
Click to collapse
That is exactly what he is saying, yes =)

Thanks guys, I'm gonna take a look at your recommendations as soon as I get some spare time.

Do all the trinitys have voodoo
Sent from my bionix nexus s

mrnexus said:
Do all the trinitys have voodoo
Sent from my bionix nexus s
Click to expand...
Click to collapse
No, only the most recent ones.

kenvan19 said:
No, only the most recent ones.
Click to expand...
Click to collapse
Such as:
Sent from my bionix nexus s

[Q] Overclocking ROM-free

I want to overclock the NS without having to replace the rom. Would this be possible? Are there additional risk associated with overclocking without replacing the ROM?
Thanks in advance!

Yes you can. All you need is root and clockwork recovery. Then download Netarchy's kernel. I know for sure that his kernel works on stock rom since he said so himself. I don't know about Trinity kernel though.

I run stock and I've tried both the trinity stock kernel and netarchy cfs kernel OC @ 1.2ghz. Personally I've had better results on the netarchy kernel.
Sent from my Nexus S

Can I put the stock kernel if I don't like the netarchy kernel? Because I use Bluetooth and wifi always and i just wanted to get a little bit more of my NS!

Make a nandroid backup of the stock rom then flash the kernel. I use netarchy every day and am usually on wifi with my bt earpiece in.
Sent from my Darkginger CM7 Google Nexus S!

I'm having a hard time finding how to flash the kernel (found a lot about how to flash the ROM though).
Would someone link me a FAQ or list some quick instructions on how to go about it?
I have ROM manager installed already (woot!)
Thanks again!

catchsomezz said:
I'm having a hard time finding how to flash the kernel (found a lot about how to flash the ROM though).
Would someone link me a FAQ or list some quick instructions on how to go about it?
I have ROM manager installed already (woot!)
Thanks again!
Click to expand...
Click to collapse
same thing as flashing a ROM.
just make sure if you're flashing a kernel over stock.. make sure its the kernel built for the "stock" rom and not a kernel for CM7 or Bionix etc

catchsomezz said:
I'm having a hard time finding how to flash the kernel (found a lot about how to flash the ROM though).
Would someone link me a FAQ or list some quick instructions on how to go about it?
I have ROM manager installed already (woot!)
Thanks again!
Click to expand...
Click to collapse
Assuming the kernel you want is clockwork compatible, put the zip file of it in your sdcard.
Boot to clockwork recovery either via ROM Mgr (if you're rooted) or via fastboot if you're not.
In Clockwork, find the menu option to install a update/file/zip from sdcard. Select that option, then navigate with the volume keys to the zip file for the kernel. Select it by pushing the power button. Select and answer yes for the are you sure warning. Wait for it to give you a update applied successfully message.
Navigate up to where you can select reboot, and reboot.
You should be on your new kernel.
I WOULD ALWAYS RUN A NAND BACKUP FROM CLOCKWORK BEFORE MESSING WITH THIS STUFF. And ideally, I would keep a copy of that backup on my laptop or dropbox account, not just my sdcard on the phone.

Thanks for all your (very quick) help!
I'm currently running Netarchy's 1.2.2 BFS @ 1.3 and it definitely feels a big snappier with loading some programs

I put today the netarchy kernel 1.2.2 and i have one question...
Where is the VooDoo Improvements? I didn't find the application!
For me the kernel is stable and wifi works even when bluetooth is disabled!

WI FI

I just got my new phone and have rooted it (i did have CM7 on it but im on stock atm again.)
What my problem is whenever i load any custom kernel, wi fi just breaks.
Ill go to wireless settings, click the check box, then it just says 'error'
anyone heard of this?

bringonblink said:
I just got my new phone and have rooted it (i did have CM7 on it but im on stock atm again.)
What my problem is whenever i load any custom kernel, wi fi just breaks.
Ill go to wireless settings, click the check box, then it just says 'error'
anyone heard of this?
Click to expand...
Click to collapse
When you load the kernel are you flashing the zimage manually or using a packaged update.zip that includes the wifi module for that kernel?

all im doing is using flashboot to flash the .img.
no idea how to flash it properly, could use your help

bringonblink said:
all im doing is using flashboot to flash the .img.
no idea how to flash it properly, could use your help
Click to expand...
Click to collapse
Are you building the kernel and boot image yourself or pulling them from somewhere?

I just downloaded netarchys 1.2.4 cfs, and extracted the .img and fastbooted it onto the phone.
What i think you're saying is that this is not the correct method to flash the kernel because the other folders are not being put on to the phone (hence broken wi fi)
If thats the case just need help to flash the kernel properly

bringonblink said:
I just downloaded netarchys 1.2.4 cfs, and extracted the .img and fastbooted it onto the phone.
What i think you're saying is that this is not the correct method to flash the kernel because the other folders are not being put on to the phone (hence broken wi fi)
If thats the case just need help to flash the kernel properly
Click to expand...
Click to collapse
Ah, indeed
So, that zip is meant to be applied via a custom recovery (CWM). It will flash not only the boot image, but also copy the newly build kernel modules, create a custom /etc/init.d and install busybox.
By flashing just the boot image you are missing the rebuilt modules and the custom init.d (which mounts /data with noauto_da_alloc, etc and sets windowsmgr.max_events_per_sec=72 for better scolling performance. As a result of not having the rebuilt kernel modules when the network module tries to load (bcm4329.ko) the version number won't match the kernel and it will fail to load. If you check dmesg you'll see it complaining
Flash this via a custom recovery and you should be fine (just place the entire zip on your device and then chose it from CWM).

right, thanks that clears that up.
however, i have another problem now!
Basically i flashed the netarchy kernel, realized i had no wifi, did a factory reset thinking ill get back to stock, however im stuck with this netarchy kernel AND ive lost CWM.
3G is being a pain and not downloading properly etc.
Is there any way for me to reset and just flash CM7 and Netarchy 1.2.4
im outta ideas :/ thanks for the help!

bringonblink said:
right, thanks that clears that up.
however, i have another problem now!
Basically i flashed the netarchy kernel, realized i had no wifi, did a factory reset thinking ill get back to stock, however im stuck with this netarchy kernel AND ive lost CWM.
3G is being a pain and not downloading properly etc.
Is there any way for me to reset and just flash CM7 and Netarchy 1.2.4
im outta ideas :/ thanks for the help!
Click to expand...
Click to collapse
When you reboot on a stock rom there is a script that checks recovery and if it is not stock it will reflash the stock recovery. This is an easy fix though. If you want to stay on stock you can flash CWM through fastboot, flash the SU binary and then rename/delete the script (/etc/install-recovery.sh or something like that).
If you want to just flash CM7 then just download the full zip and place it on the phone. Flash CWM through fastboot, boot into recovery and flash CM7 as desired (RC or nightlies). Then go ahead and apply the appropriate netarchy kernel - there's a separate version for CM IIRC. Make sure you do a full wipe before you flash CM7.

Ok so im downloading rom manager onto my phone, downloading CM7 on pc, then will transfer to phone (whole zip right?) then i just reboot in recovery, wipe and flash CM7, and THEN start on the kernel lol
Ok thanks ill keep ya updated really appreciate it
edit
Thanks a lot booted and rooted running CM7 and Netarchy

Restoring to stock OS

If I restore to the stock OS, will it replace the Imoseyon 4.0 kernel or will I have to do that manually? I know im going to have to turn off voodoo before doing so, but otherwise im not sure.

didureboot said:
If I restore to the stock OS, will it replace the Imoseyon 4.0 kernel or will I have to do that manually? I know im going to have to turn off voodoo before doing so, but otherwise im not sure.
Click to expand...
Click to collapse
If you flash a full stock Odin, it will replace everything, kernel included. If you follow the instructions in the Fix Your Phone thread, it will even repartition everything clean as well, though that's probably not necessary unless you're having boot issues.

Kernel for JB

Hi,
I tried several kernels for JB. Air, Matrix. None of them worked for me. After flashing it, it won't boot the system and turn off the device. I currently use JellyBelly 1.5. Any idea? Is it ROM bug? Thanks!

devcager said:
Hi,
I tried several kernels for JB. Air, Matrix. None of them worked for me. After flashing it, it won't boot the system and turn off the device. I currently use JellyBelly 1.5. Any idea? Is it ROM bug? Thanks!
Click to expand...
Click to collapse
I can't use Adam's Jelly Belly rom, as I have a NS4g, but I do follow his work. I believe that his rom comes with Thalamus kernel, and if you want to flash a different kernel, there is a file which needs to be deleted before doing so. There was quite a discussion about all this in his thread in the development forum. That's where you can figure it out ... good luck!

same for me
Hey i also tried to flash thalamus kernel but my phone didnt start it was hanged up on the boot screen. I am using Nexus S i9023 SCLD version stock rom 4.1.1 build JRO03E and it is rooted.
Can anyone please help me and also which other kernels are supported on stock rom.

There's a script you must delete in the init.d to use another kernel in Jelly Belly 0.1.5
Otherwise, your phone will poweroff

panks_4ever said:
Hey i also tried to flash thalamus kernel but my phone didnt start it was hanged up on the boot screen. I am using Nexus S i9023 SCLD version stock rom 4.1.1 build JRO03E and it is rooted.
Can anyone please help me and also which other kernels are supported on stock rom.
Click to expand...
Click to collapse
i have also a i9023 and i have allredy flashed bedalus kernel, thalamus and air kernel also matrix and vta2 worked for me..
i use JRO03E DX stock ROM..never had a problem
S.R.

(I use stock JB with Air #153, and got i9023. No OC, no NSTools, yet. I have no problem.)
On stock:
Try to do a factory reset/wipe data, or reflash the OS from scratch using factory images. And right after flashing the rom, flash the kernel. Even before installing any apps.
On JBelly:
For this, I think the Thalamus kernel is the best, the rom is come with it, so they made for each other If this kernel works with it, i think it is unnecessary to switch to another kernel right now.
Because JB kernels are not final yet, are "immature", there can be compatibility issues, collisions between (certain functions of) roms and kernels.
After a 2 or 3 releases, both on rom and kernel side, there will be more complete and stable versions.

Have you tried to fix permissions ?

Go to /etc/init.d/ folder and delete a file called 'kernel'. You can read it first if you want.
This is basically a hack that AdamG added to avoid everyone changing kernels and reporting problems about the ROM. He only allows thalamus kernel.

Can please provide me detailed steps of how to flash a thalamus kernel on stock jb because i think the procedure is wrong. I did the following steps:
1. Reboot into recovery( I am using Clockwork Mod recovery touch 6.0.1.0)
2. Wipe Cache partition
3. Wipe Dalvik cache
4. Install the kernel zip file
And after i tried restarting my phone but it hanged up on the boot screen.
Please someone advise me the correct steps if this is wrong
. Thanks in advance
Sent from my Nexus S using xda app-developers app

panks_4ever said:
1. Reboot into recovery( I am using Clockwork Mod recovery touch 6.0.1.0)
2. Wipe Cache partition
3. Wipe Dalvik cache
4. Install the kernel zip file
Click to expand...
Click to collapse
I think the cache partition wipe is your problem. You shouldn't have to wipe anything if you're flashing _thalamus' kernel on stock JB. Just flash and reboot. I've done it plenty of times without problems.

devcager said:
Hi,
I tried several kernels for JB. Air, Matrix. None of them worked for me. After flashing it, it won't boot the system and turn off the device. I currently use JellyBelly 1.5. Any idea? Is it ROM bug? Thanks!
Click to expand...
Click to collapse
To not have to deal with third party kernel support there is /system/etc/init.d/00kernel that simply powers off your phone if you flash another kernel.
Flash the rom to boot it, delete the file, then flash any kernel you want as you usually would.

charchuck said:
I think the cache partition wipe is your problem. You shouldn't have to wipe anything if you're flashing _thalamus' kernel on stock JB. Just flash and reboot. I've done it plenty of times without problems.
Click to expand...
Click to collapse
wipe is not needed...
but fix permissions should be done...but I´m not sure thats required for all kernel.
S.R.

so this are the final steps...
shivasrage said:
wipe is not needed...
but fix permissions should be done...but I´m not sure thats required for all kernel.
S.R.
Click to expand...
Click to collapse
Firstly, thanks for replying. I need to do the folloing steps (just to confirm because its better to do so and also i dont want to again restore a backup)
1. Reboot into recovery
2. Wipe Dalvik Cache
3. Install the kernel zip file
4. Fix Permissions
or 3. Fix Permissions, and then
4. Install kernel zip file
Please advise the correct steps and thanks in advance.
(I know i am getting a bit more concerned because i had it twice and i am not able to flash the same. So, I am trying to get a correct way and this the best place to ask. XDA rocksssssss<3<3<3)

panks_4ever said:
Firstly, thanks for replying. I need to do the folloing steps (just to confirm because its better to do so and also i dont want to again restore a backup)
1. Reboot into recovery
2. Wipe Dalvik Cache
3. Install the kernel zip file
4. Fix Permissions
or 3. Fix Permissions, and then
4. Install kernel zip file
Please advise the correct steps and thanks in advance.
(I know i am getting a bit more concerned because i had it twice and i am not able to flash the same. So, I am trying to get a correct way and this the best place to ask. XDA rocksssssss<3<3<3)
Click to expand...
Click to collapse
There's no need for all that... flash jellybelly latest version, boot with the original kernel and delete /system/etc/init.d/00kernel with Rom Toolbox or Root explorer. After that you can flash the kernel that you want. Mind that this will only work for version 0.1.5.1, versions after that one will probably have a framework check to prevent flashing 3rd party kernels because the dev of jellybelly doesn't want to be disturbed with bugs caused by other kernels then not the Thalamus one.
---------- Post added at 08:55 AM ---------- Previous post was at 08:34 AM ----------
Checked. Version 1.0.0 only allows Thalamus kernel to be flashed. A framework check doesn't allow 3rd party kernels to be fixed so either you stick to the stock kernel of jellybelly or get another ROM so you can use other Kernels.

Panks_4ever
What I always do.. (phone i9023 X-JB Stock).
1. flash kernel zip
2. wipe cache
3. wipe dalvik
4. fix permissions
i only know that thalamus kernel don´t need any wipe...also i don´t know if this procedure is right or not
and i don´t won´t discuss about i only can report what worked for me so try it or not its your decision....
S.R.

thank you
shivasrage said:
Panks_4ever
What I always do.. (phone i9023 X-JB Stock).
1. flash kernel zip
2. wipe cache
3. wipe dalvik
4. fix permissions
i only know that thalamus kernel don´t need any wipe...also i don´t know if this procedure is right or not
and i don´t won´t discuss about i only can report what worked for me so try it or not its your decision....
S.R.
Click to expand...
Click to collapse
DeuXGod said:
There's no need for all that... flash jellybelly latest version, boot with the original kernel and delete /system/etc/init.d/00kernel with Rom Toolbox or Root explorer. After that you can flash the kernel that you want. Mind that this will only work for version 0.1.5.1, versions after that one will probably have a framework check to prevent flashing 3rd party kernels because the dev of jellybelly doesn't want to be disturbed with bugs caused by other kernels then not the Thalamus one.
---------- Post added at 08:55 AM ---------- Previous post was at 08:34 AM ----------
Checked. Version 1.0.0 only allows Thalamus kernel to be flashed. A framework check doesn't allow 3rd party kernels to be fixed so either you stick to the stock kernel of jellybelly or get another ROM so you can use other Kernels.
Click to expand...
Click to collapse
Thank you shivasrage and DeuXGod. I am surely goona try out this, i am being eagerly waiting to flash a custom kernel because as compared to ICS i feel JB is eating up more battery. Thank you so much:good: