Develop Bugs

[Q] Semi-bricked Nexus and not sure what to do

So I made a mistake and I tried to flash the newest aokp build 3 without a backup. I got my new phone a while back and never made a backup.
I flashed build 3 and (accidentally) some old gapps and I kept getting stuck on the Google screen.
Next I tried pushing files through the Gnex tool kit and manually through fastboot. I keep getting errors that there is no insecure boot or that the device is not connected. attempts at a temporary insecure boot on the tool kit fail.
Next I tried a wipe and then just installing build 3 without google apps so I could add the correct one after boot, but it is again stuck.
So now I'm really not sure what to do. Any suggestions?

Rule number 1 : STOP using toolkits!!
now, can you get into cwm recovery?

Yes, I can gt into twrp everything I did except for trying to push the last files was through twrp
by the way, I have a Verizon Nexus
And as a side comment: The tool kit was used as a last ditch effort. The toolkit had nothing to do with bricking the device. The toolkit has been extremely useful for unlocking and rooting multiple devices quickly.

You could eithther try to flash back to stock or you could boot into TWRP & adb push a different ROM. (You did try Wipe Data / Factory Reset right?)

MK17 said:
Yes, I can gt into twrp everything I did except for trying to push the last files was through twrp
by the way, I have a Verizon Nexus
And as a side comment: The tool kit was used as a last ditch effort. The toolkit had nothing to do with bricking the device. The toolkit has been extremely useful for unlocking and rooting multiple devices quickly.
Click to expand...
Click to collapse
I think what thegtfusion was trying to say was: if you wouldn't have used a toolkit in the past, you would have known how to fix your bootloop.
Buy anyway:
1) Boot into recovery and plug into your PC
2) Open a command prompt (in the folder where you have adb.exe and fastboot.exe)
3) Push the ROM (and kernel if it doesn't come with it) you want to flash to your device: adb push /path/to/ROM.zip /sdcard/
4) Reboot into fastboot mode
5) Erase your old ROM: fastboot erase system
6) Erase your old kernel: fastboot erase boot
7) Reboot into recovery
8) Wipe /data and /cache
9) Flash your ROM & kernel in recovery
10) Reboot. Done.
EDIT: Ninja'd by 3rdstring!

Screwing up is part of the learning process. It's actually a great way to learn how your phone really works.

Thanks for the reply. For some reason I can't get my device to be recognized on my new computer. I downloaded drivers, adb and fastboot and rebooted everything but it didn't work. I'll have to retry again on my other computer tomorrow.

MK17 said:
Thanks for the reply. For some reason I can't get my device to be recognized on my new computer. I downloaded drivers, adb and fastboot and rebooted everything but it didn't work. I'll have to retry again on my other computer tomorrow.
Click to expand...
Click to collapse
Try uninstalling all drivers and reinstalling them.
Sent from my Galaxy Nexus using xda premium

Drivers

Thanks for the drivers. I uninstalled all of the drivers and used the universal one. Everything seems to work until I run 'adb devices' and my Galaxy Nexus is not listed.
I feel that my device is not getting seen because of something I have wrong, but after adb, fastboot, and the correct drivers I'm not sure.
PS - Even with the universal driver I still have to run adb and fastboot from the original directory that I installed them correct? I don't run them from the driver in anyway correct?

MK17 said:
Thanks for the drivers. I uninstalled all of the drivers and used the universal one. Everything seems to work until I run 'adb devices' and my Galaxy Nexus is not listed.
I feel that my device is not getting seen because of something I have wrong, but after adb, fastboot, and the correct drivers I'm not sure.
PS - Even with the universal driver I still have to run adb and fastboot from the original directory that I installed them correct? I don't run them from the driver in anyway correct?
Click to expand...
Click to collapse
did you install android-sdk (and added adb/fastboot to your $PATH) or are you using binary versions of adb and fastboot downloaded elsewhere?
if it's the latter, commands should be run from the directory where you extracted them.
about the drivers, i think you need to go to device manager and update drivers manually to the ones you installed (refered here in the post before mine), assuming you're on windows.
sent from my i9250

You're booted into TWRP when trying adb?

Fixed! I ended up booting into recovery and the device was recognized in adb there. I was able to push fresh copies of aokp build 3 and gapps (my original build 3 download started failing) and now I just got done initiating swagger!

MK17 said:
Fixed! I ended up booting into recovery and the device was recognized in adb there. I was able to push fresh copies of aokp build 3 and gapps (my original build 3 download started failing) and now I just got done initiating swagger!
Click to expand...
Click to collapse
he didnt have usb debugging on.
sent from my i9250

Just for understanding, USB debugging is only activated through recovery?

It's also under settings >> developer options so you can use adb while the android is running.

3rdstring said:
It's also under settings >> developer options so you can use adb while the android is running.
Click to expand...
Click to collapse
Of course,but that is hard to get to when your phone doesn't boot

MK17 said:
Of course,but that is hard to get to when your phone doesn't boot
Click to expand...
Click to collapse
USB Debugging needs to be enabled in Android for ADB to work in Android.
CWM and TWRP have USB Debugging enabled by default, so ADB will work fine in recovery with no other action from the user.

>>URGENT<<.Nexus 7 Google Screen..Cant access Recovery. AND not recognizing Nexus 7

>>URGENT<<.Nexus 7 Google Screen..Cant access Recovery. AND not recognizing Nexus 7
>>URGENT<<.Nexus 7 Google Screen stuck.Cant access Recovery. AND Windows 7 wont recognize my Nexus 7 2013
Nexus 7 2013 is stuck on Google screen. i just had and when i first booted it fooling around with a custom rom(cyanogenmod) that for some reason did not have android market/google play store. I then decided i wanted to return it to stock and at first for some reason I have a MAJOR hassle with downloading the drivers. Reguardless of the drivers the nexus 7 either becomes unknown device, other, or Android Phone. I have downloaded them from source, mirrors, Wugs,Nexus toolkit. Whenever i even attempt anything with Wugs Kit, it just says some error about ADB and if not that Fast boot. I tried installing fastboot and ABD and also tried this application called Minimal ADB and Fastboot but got similar results. I attempted it to restore to stock rom with MANY different types of tutorials including copying and pasting then to cmd and use the "flash-all.bat" command. All it would ever do is crash whenever it got to fastboot.exe. Also there is another issue with Android SDK when i attempted to use it to resolve this. It was just very confusing on how it operated because i did not understand the directions as well as the driver issue. I also attempted Unified Android Toolkit but it could not recognize my Nexus 7 as a device (driver problem again).This is very VERY frustrating because it will not work for me. i just want to get my nexus back to stock then root again without a custom rom. For some reason my computer recognizes it as an android phone and will not let it register as anything else even with correct build file. i can no longer access usb debugging because in one of the many tutorials it said to: clear cache. divalk cache, wipe data, format data, format system, etc. you get the point. I have NO IDEA how to fix this i have been at this for at least 6 hours straight. Please can somebody help me resolve this i do not know what to do anymore and it is VERY important that i get this fixed. It is really stressing me out.
Thank you..

Here are sources I know will work.
Driver: http://developer.android.com/sdk/win-usb.html
Fastboot and ADB: http://forum.xda-developers.com/showthread.php?t=2225405
https://developers.google.com/android/nexus/images#razor
That third one has "flash-all.bat" to flash the stock recovery and ROM. The bootloader must be unlocked first, which I presume is the case since you've flashed CM. (BTW, CM requires flashing a separate gapps file, which is why you didn't have Play Store installed.) With what you've been flashing, I suggest a full wipe before flashing:
fastboot erase boot
fastboot erase cache
fastboot erase recovery
fastboot erase system
fastboot erase userdata
One thing to make sure of: open the command prompt as an administrator, otherwise cmd.exe won't have enough rights.

To get back to stock download the stock images from:
https://developers.google.com/android/nexus/images
The Nexus 7 2013 is aka razor
once you download them put the device in fastboot mode Vol down + Power
then run flash-all.bat
For it not recognizing things, uninstall all Nexus device driver's.
Then install ones you KNOW work wug toolkit I guess a lot of peeps talk about and it seems to work well.
I would prefer the factory driver's if you are having issues to eliminate with 3rd party software etc..
Hopefully that helps.

[Solved] Soft Bricked Nexus 7 (2013)

Hey there,
i have a Nexus 7 (2013) with android 4.4.2 (KOT49H). I unlocked the bootloader with wugfresh´s toolkit - so far no problems. Then i tried to root... The toolkit installed TWRP and launched into recovery to install the needed root files, but the device remained there...and nothing happened. On the PC the process froze showing the message "waiting for device". I rebooted the device manually from recovery. After the reboot i had no root access.
Because of these problems i decided to use the "Flash Stock + Unroot" option in the toolkit. First i completely reinstalled all related drivers with the full driver intallation guide and i got the "Success" message after testing. I enabled usb-debugging and went through the restore process. Then i got the message "FAILED (data transfer failure (Too many links))". My device remained in bootloader mode. At least it is possible to boot into bootloader mode every time. But when i try to start the device normal it freezes on the google logo, because the rom is partially wiped.
What can i do to get my device to stock firmware without to exacerbate the situation? Should i enable "Force Flash Mode"?
Please help me, thank you very much!
I attached the log below...

Ditch the toolkit. Download the Google revert to stock package, unzip it, connect your device in fastboot and run the flash all batch file
Sent from my Nexus 7 using Tapatalk
---------- Post added at 03:36 PM ---------- Previous post was at 03:32 PM ----------
Refer to this guide http://www.androidpolice.com/2013/0...stock-using-a-full-factory-image-and-root-it/
Sent from my Nexus 7 using Tapatalk

SwoRNLeaDejZ said:
Ditch the toolkit. Download the Google revert to stock package, unzip it, connect your device in fastboot and run the flash all batch file
Sent from my Nexus 7 using Tapatalk
---------- Post added at 03:36 PM ---------- Previous post was at 03:32 PM ----------
Refer to this guide http://www.androidpolice.com/2013/0...stock-using-a-full-factory-image-and-root-it/
Sent from my Nexus 7 using Tapatalk
Click to expand...
Click to collapse
Thanks! I will try this method. Is it necessary to install some further specific fastboot drivers or are the ones installed by the toolkit sufficient? USB-Debugging was checked before in developer options but the android os is partially wiped. So will this be a problem? Is there a possibility to control if the device is recocnized correctly before i run the batch file. I think i don´t have to remove the "-w" from the fastboot update command because everything has to be wiped.

Just follow the tutorial, you should be good to go. And the adb and fastboot drivers are the same.
Sent from my LG-MS770 using Tapatalk

SwoRNLeaDejZ said:
Just follow the tutorial, you should be good to go. And the adb and fastboot drivers are the same.
Sent from my LG-MS770 using Tapatalk
Click to expand...
Click to collapse
Ok i started the batchfile but it said that the fastboot command couldn´t be found. Then i copied the 5 files of the unpacked factory image into the sdk -> platform tools directory. Am i right? Now when i run the flash-all file it says "waiting for device" I do this for the first time so i´m a little bit uncertain. Is all i have to do now to connect my nexus in fastboot mode? Thank you very much again!
Here are some screenshots...

Have you looked in Device Manager from Windows if the hardwaredriver of device is correctly installed. While in recovery and usb-connected type 'adb devices' in Command Window to see if there is connnection before flashing.
I had the same problem in Windows 8 first time flashing. Only way to get driver and device in recovery mode working in my case: In Device manager I clicked 'update driver' of 'unknown device', browsed to unpacked driver Folder and let Windows install correctly.
Verstuurd vanaf mijn Nexus 7 met Tapatalk

juliatan said:
Have you looked in Device Manager from Windows if the hardwaredriver of device is correctly installed. While in recovery and usb-connected type 'adb devices' in Command Window to see if there is connnection before flashing.
I had the same problem in Windows 8 first time flashing. Only way to get driver and device in recovery mode working in my case: In Device manager I clicked 'update driver' of 'unknown device', browsed to unpacked driver Folder and let Windows install correctly.
Verstuurd vanaf mijn Nexus 7 met Tapatalk
Click to expand...
Click to collapse
In the driver manager there is an android device connected "Google Nexus BootLoader Interface" but when i run the command "adb devices" i don´t get an device listed although i am connected in bootloader mode. Recovery isn´t working anymore (shows android with triangle), because of the bad factory reset with the toolkit. So what can i do to get my device recognized? Actually the needed drivers should be okay, because the universal drivers were installed via the toolkit and i was able to unlock the bootloader etc. What i´m doing wrong?
Thank you for help.

I appologize, but this is out of ny league. I would first try that toolkit-thread. I am sure there will be a repair thread too. Good luck.
Verstuurd vanaf mijn Nexus 7 met Tapatalk

Blizzard300 said:
In the driver manager there is an android device connected "Google Nexus BootLoader Interface" but when i run the command "adb devices" i don´t get an device listed although i am connected in bootloader mode. Recovery isn´t working anymore (shows android with triangle), because of the bad factory reset with the toolkit. So what can i do to get my device recognized? Actually the needed drivers should be okay, because the universal drivers were installed via the toolkit and i was able to unlock the bootloader etc. What i´m doing wrong?
Thank you for help.
Click to expand...
Click to collapse
When you are connected to the computer in the bootloader (on the N7), what does it say when you type "fastboot devices"? (without the quotation marks)

juliatan said:
I appologize, but this is out of ny league. I would first try that toolkit-thread. I am sure there will be a repair thread too. Good luck.
Verstuurd vanaf mijn Nexus 7 met Tapatalk
Click to expand...
Click to collapse
Thanks, i will do that. After reading some indications in the toolkit thread i found out that i am able to access stock recovery

charesa39 said:
When you are connected to the computer in the bootloader (on the N7), what does it say when you type "fastboot devices"? (without the quotation marks)
Click to expand...
Click to collapse
Thanks, i think you found the solution When i use the command "fastboot devices" i get this: 08f34cbd
Does it mean everything is correctly installed and i´m ready to flash the factory image? I am also asking me if it was right to extract all the files of the razor-kot49h factory image into the platform tools directory of sdk, but otherwise when i just executed the flash-all file somewhere on the computer there were failure messages, so i assume it should be right this way. Thank you!

Blizzard300 said:
Thanks, i think you found the solution When i use the command "fastboot devices" i get this: 08f34cbd
Does it mean everything is correctly installed and i´m ready to flash the factory image? I am also asking me if it was right to extract all the files of the razor-kot49h factory image into the platform tools directory of sdk, but otherwise when i just executed the flash-all file somewhere on the computer there were failure messages, so i assume it should be right this way. Thank you!
Click to expand...
Click to collapse
Yes it does! Nothing was coming up when you typed "adb devices" because that's only when you're in the OS after it completely boots into it's ROM. Fastboot is for when it's in the bootloader menu. And yes, you are correct regarding the factory image zip. Extract everything out of the zip (I can't remember if there's a zip inside that zip, but I think there is). Make sure you unzip that as well if there is. Then, place all the image files into that platform-tools folder. So you should have image files for Bootloader, System, Userdata, Boot, Recovery and Cache. I don't think the cache is necessary, but I suppose it wouldn't hurt to flash it as well.
I followed these steps when restoring the factory image on my N7: http://forum.xda-developers.com/showthread.php?t=2513701
I used Method 2 from the OP. Obviously, those instructions are for the Nexus 5, but it'll work. Just skip over the part where it says "flashboot flash radio". So fastboot flash the bootloader, reboot bootloader, fastboot system, fastboot userdata, fastboot boot, fastboot recovery, fastboot erase cache (or fastboot cache if you want to flash the cache image from the factory image zip). Then, manually select "Recovery Mode" on the phone using the volume buttons on the N7. It'll show that Android on it's back with the red exclamation mark. Hit Power + Vol Up at the same time and it'll show the stock recovery menu. Select "Wipe data/Factory data reset" and reboot. You should be good to go.

Unzip the tar.gz and then double click flash all, no need to unzip anything inside the tar.gz. and yes, adb commands only work from inside the os, you need to use fastboot commands when in the bootloader. I would suggest reading up on it, very useful information.
Sent from my LG-MS770 using Tapatalk

Yeah, all went perfectly well! After the factory image was restored i flashed twrp with fastboot, installed super su over sideload and then busy box from the playstore. I immediately did a full backup in the recovery At this point i want to say thank you to all who helped me! You are awesome!
First i was afraid that my nexus couldn´t be repairable anymore. So i´m really happy now that everything worked.

Blizzard300 said:
Yeah, all went perfectly well! After the factory image was restored i flashed twrp with fastboot, installed super su over sideload and then busy box from the playstore. I immediately did a full backup in the recovery At this point i want to say thank you to all who helped me! You are awesome!
First i was afraid that my nexus couldn´t be repairable anymore. So i´m really happy now that everything worked.
Click to expand...
Click to collapse
Glad it all worked out for you. :thumbup:
Sent from my Nexus 5 using xda app-developers app

Partition table doesn't exist

Hey all,
So I seem to have soft bricked my tablet (Nexus 7 2013 LTE). I can get into fastboot mode (but not into the recovery menu) then I am stuck on the Google logo. Does this mean the device is repairable?
Device manager on Windows shows the tablet as
- an unknown device (no drivers installed / Samsung (Wugfresh) / Google drivers)
- Android bootloader interface (Snoop05's tool)
- Android ADB Interface (PDAnet (Wugfresh)).
On all of them the driver is not correctly installed and I have the exclamation mark showing on device manager. I am unable to access the tablet via fastboot or ADB at this time.
I have tried every permutation I can think of so am turning to the hive mind for advice.
To compound matters I am in Turkey and I don't speak Turkish. I've been in an internet cafe for about 5 hours now and it's 1am (Turkish keyboards have an ı where i should be and you can imagine how many times I have mistyped). I am on a year long cycle tour and the tablet has my music, books, guidebooks and dictionaries on it so I am pretty hacked off. Especially given that I've only just arrived...
I did manage to connect via ADB yesterday but ran out of time as I was borrowing someone's computer and can't replicate the steps. Gah!
I have backups of all my data so essentially I would just like to factory reset. Any help gratefully received!
Thanks,
Don

Well, I found the right combination of drivers (Snoop05's tool then PDANet on Wugfresh) and can now see the device via fastboot so I have unlocked it. However whenever I try and flash boot / system / recovery, etc via fastboot I'm receiving an error 'remote: partition table doesn't exist'. Any ideas, people?

Probably useful to add that the problem was initially caused when I removed the SIM card whilst the unit was switched on. I received a message asking me to reboot and it has been bricked since. Also, I was runing stock unrooted.
Thanks

I have now tried every toolkit I can find but still no joy. I seem to have corrupted my partition table which is preventing me writing anything to the device.
To confirm - I can boot into fastboot mode and can see the device via fastboot using command line and can unlock it using 'fastboot oem unlock'. I have the images to write using 'fastboot flash boot/recovery/system [image location] but nothing will let me write to the device without receiving the error 'FAILED - remote: partition table doesn't exist'.
I have searched everywhere and can't find very much. Is the device recoverable or have I fecked it...? I need to get out of internet cafes and onto my bike...
Cheers in advance

Gulp! 100+ views and no replies...does no-one want to break it to me that my lovely tablet is beyond help! Is the only solution some wizardry using GParted or something? I'm already in way over my head.
I'm only bugging you all as I am running out of time in town and need to head off into the wilds. I have tonight and that's it for at least a week. It would be nice to have some company ie books and music...oh and a Turkish dictionary and translator...poor attempt to drum up sympathy I know.

I'll be honest, I've never seen such an issue as yours but it's worth a try since you got fastboot to do fastboot format of all your partitions and see if it helps to flash factory image. Something like fastboot format system for example.
Sorry I can't be more help
Nexus 7 LTE
Carbon Rom
Faux Kernel

dondelion said:
I have now tried every toolkit I can find but still no joy. I seem to have corrupted my partition table which is preventing me writing anything to the device.
To confirm - I can boot into fastboot mode and can see the device via fastboot using command line and can unlock it using 'fastboot oem unlock'. I have the images to write using 'fastboot flash boot/recovery/system [image location] but nothing will let me write to the device without receiving the error 'FAILED - remote: partition table doesn't exist'.
I have searched everywhere and can't find very much. Is the device recoverable or have I fecked it...? I need to get out of internet cafes and onto my bike...
Cheers in advance
Click to expand...
Click to collapse
Remove Wug's drivers and what ever other old drivers you have and follow this tutorial http://forum.xda-developers.com/showthread.php?t=2381582 make sure your getting for the data and not WiFi only. Get them old drivers out of there first.
Sent from my Nexus 7 Flo running Odex SinLess ROM 4.4.2 with ElementalX kernel using XDA Premium 4 mobile app

Raverbunny said:
I'll be honest, I've never seen such an issue as yours but it's worth a try since you got fastboot to do fastboot format of all your partitions and see if it helps to flash factory image. Something like fastboot format system for example.
Sorry I can't be more help
Nexus 7 LTE
Carbon Rom
Faux Kernel
Click to expand...
Click to collapse
Fastboot format still appears to require an intact partition table as I still receive an error - 'FAILED (command write failed (invalid argument))' but thank for the response.
LinearEquation said:
Remove Wug's drivers and what ever other old drivers you have and follow this tutorial http://forum.xda-developers.com/showthread.php?t=2381582 make sure your getting for the data and not WiFi only. Get them old drivers out of there first.
Sent from my Nexus 7 Flo running Odex SinLess ROM 4.4.2 with ElementalX kernel using XDA Premium 4 mobile app
Click to expand...
Click to collapse
I tried this but same problem - no partition table so unable write anything to the device, thanks...

don, did you ever solve this?
I am having a similar problem but cannot unlock the device.

i have the same problem ....i just usedf flo-ebb clamours repartition and it wiped out all my partions i can only access fast boot but cant install anything as it says " no such partition "

Is your bootloader unlocked? If so, you should be able to flash the factory image in fastboot.
If not, you should be able to sideload the OTA in recovery.

Nexus 7 - 2nd gen: update failed to Lollipop 5.1

HI everyone,
I updated "successfully" from Kitkat to 5.0.2 on my rooted (stock ROM) Nexus 7 second gen.
Unfortunately, when I tried to upgrade to 5.1 everything seem to be normal until the device rebooted and it went through the "update process". 3/4 the way through, the green droid went on his back and the "ERROR" message appeared.
I wiped the cache partition but that doesn't help. I tried to download the update in safe mode, but no success. I also find it odd that each time I reboot my device, I get a message from Android that it is "updating my apps".
If I didn't have any apps and a lot of data on my Nexus, I would wipe the device clean but I'd rather avoid this, if at all possible.
Is there a way to upgrade to 5.1 or reinstall 5.0.2 without losing everything?
Thanks

Michael Carleone said:
Is there a way to upgrade to 5.1 or reinstall 5.0.2 without losing everything?
Click to expand...
Click to collapse
No problem. As you rooted it before then presumably it is unlocked and equipped with custom recovery, so all you have to do is:
boot TWRP
connect PC
transfer data and APKs to PC
flash OS
If you don't have TWRP installed, then boot it like this fastboot boot twrp-3.0.2-0-flo.img

k23m said:
No problem. As you rooted it before then presumably it is unlocked and equipped with custom recovery, so all you have to do is:
boot TWRP
connect PC
transfer data and APKs to PC
flash OS
If you don't have TWRP installed, then boot it like this fastboot boot twrp-3.0.2-0-flo.img
Click to expand...
Click to collapse
Hi,
Thanks for the reply. I rooted with Kingroot. I don't believe I have a custom recovery. The bootloader is locked as shown when I boot into recovery mode.
I want to avoid transferring my data and APK files to my PC.
Should I assume there is no way of reinstalling the OS without wiping out the device?Also, there is no link in the above quote: fastboot boot twrp-3.0.2-0-flo.img

Since I got no other replies, I went and restored to factory image. I do have another question. I hope I get a better response there: http://forum.xda-developers.com/nex...a/nexus-7-2013-wifi-root-marshmallow-t3515072

Thanks for the reply.
Can we compare using fastboot flashing TWRP vs Nexus Root Tool Kit: http://www.wugfresh.com/nrt/? I ended up using this utility instead because it was pretty much one click and it didn't require command lines and for whatever reason, I found instructions using fastboot a bit confusing. Which method is better or has more advantages? I left my bootloader unlocked.
Incidentally, I think there was something wrong with my Nexus image. As a result, I did use Google's instructions on how to flash etc. the OEM image. Instructions weren't ideal but I managed to figure things out: https://developers.google.com/android/images
The instructions are here which I assume would be similar if I wanted to fastboot TWRP?
To flash a system image:
Download the appropriate system image for your device below, then unzip it to a safe directory.
Connect your device to your computer over USB.
Start the device in fastboot mode with one of the following methods:
Using the adb tool: With the device powered on, execute:
adb reboot bootloader
Using a key combo: Turn the device off, then turn it on and immediately hold down the relevant key combination for your device. For example, to put a Nexus 5 ("hammerhead") into fastboot mode, press and hold Volume Up + Volume Down + Power as the device begins booting up.
If necessary, unlock the device's bootloader by running:
fastboot flashing unlock
or, for older devices, run:
fastboot oem unlock
The target device will show you a confirmation screen. (This erases all data on the target device.)
Open a terminal and navigate to the unzipped system image directory.
Execute the flash-all script. This script installs the necessary bootloader, baseband firmware(s), and operating system.
Once the script finishes, your device reboots. You should now lock the bootloader for security:
Start the device in fastboot mode again, as described above.
Execute:
fastboot flashing lock
or, for older devices, run:
fastboot oem lock
Locking bootloader will wipe the data on some devices. After locking the bootloader, if you want to flash the device again, you must run fastboot oem unlock again, which will wipe the data.
Click to expand...
Click to collapse
Also, I could've sworn that when I rooted KitKat on my Nexus, my data wasn't wiped out. I don't recall doing anything to the bootloader. I can't recall which method I used, but I know for certain I didn't use the Nexus Root Toolkit. I should've recorded my steps when I rooted.

i rooted my nexus 7 using towel root on kitkat .. i unrooted using supersu... and ota untill marhsmallow with out a problem never use kingroot as its so un stable.