How to flash android factory image without wiping your device - Unbrick your rooted android after a failed OTA update from 4.3 to 4.4 kitkat

I own a Nexus 7 WiFi (2012) on Android 4.3, unlocked and rooted, stock rom.
Long story short: I received the OTA update to android 4.4, I executed the update... and it bricked my Nexus 7.
I've been able to restore my tablet without wiping it by installing the 4.4 factory image.

Installing a factory image will wipe your device, but it's possible to modify the installation script so that it wont delete userdata, nor wipe the device.

About the rooting
When I received the OTA update for 4.4 id didn't unroot before installing it, after all I updated from 4.1 to 4.2 and from 4.2 t 4.3 without unrooting... but this time it didn't work out.
So, keep a note for myself: always unroot before applying system update.
(anyway, this kind of error happened even to person with stock unrooted tablet... so I will never know if the error I got during the update was due to my tablet being rooted)

Fixing the reboot loop
When I got the error my tablet then got stuck in a reboot cycle.
Tablet start up, and then after some time show a "no comand" error, and then reboot, and continue like this...
In this situation I wasn't unable to turn off the tablet, and I didn't want it to drain all the battery.
Looking for a fast and effective way to turn it of, I decided to open it up an detach it's battery: it's an extreme way to get the job done, and (obviously) it worked :-)
Then after some searching I found a better way that doesn't involve dismantling the tablet: simply  push Vol Down + Power at the same time, and if you push then just after the tablet started the boot sequence, this should take you to the Recovery Mode menu, from here you can turn off the tablet: push the VolDown button until you see the "Power Off device" command, and then press the power button.

Reinstalling the update
After some  searching I've decided to simply retry to update the tablet, by sideloading the update with adb.
I've followed this guide.
Here is what I did:

• I updated my android SDK by using  SDK Manager.exe
• this may update the driver of your device, so maybe the computer wont see the device when you connect it: in this case you need to go in the "device manager" and force it to update the driver  (you can find the driver in "sdk\extras\google\usb_driver") you need to install the "Android Composite ADB Interface" driver, more info here
• I downloaded the file update for my tablet (see the linked guide for this)
• I rebooted my pc
• I disabled firewall
• I disabled antivirus
• I closed any running software (dropbox, skype, gTalk....)

Then I followed the guide: powered on the tablet, go to the recovery mode, open command  prompt on my PC, sideload the update with adb sideload command and... I got another error.
So I wiped the cache from the recovery menu, and tried one more time, just to get the same error again, something like:

Error!

bla...
bla...
bla...

Symlinks and permissions...
set_metadata_recursive: some changes failed
E:Error in /tmp/update.zip
(Status 7)
Installation aborted.

here is a screenshot of the full error message:

Reinstalling the update didn't work out, so I started looking for alternative solutions.
The only solution seemed to be to reinstall a factory image.
The issue with the factory image is that they will wipe your device, and I dont want to wipe my device because reinstalling and reconfiguring all the app take a tons of time (I have about 300 app on my tablet, with file manager, dropbox, synology cloudstation file sync, multiple account, multiple calendars, email, messaging...)

So I decided to try everything I can before doing a factory reset.

After much reading, I understood that it should be possible to install factory image without wiping the device. But to do this, you need to modify the installation script.
The procedure I'm going to describe here is a mix of the information I found on various website on the net.

Keep in mind that this procedure may not work, and it may brick your tablet/phone.
I'm not responsible of any damage/malfunction to your device.
Follow the described steps only if know what you are doing.

Steps to install a factory image without wiping your device
Download the factory image for your device from this page
Decompress it in a folder, and you'll have something like that:

Then you need to edit the "flash-all.bat"
The original "flash-all.bat" looks like this:

@ECHO OFF
:: Copyright 2012 The Android Open Source Project
::
:: Licensed under the Apache License, Version 2.0 (the "License");
:: you may not use this file except in compliance with the License.
:: You may obtain a copy of the License at
::
::      http://www.apache.org/licenses/LICENSE-2.0
::
:: Unless required by applicable law or agreed to in writing, software
:: distributed under the License is distributed on an "AS IS" BASIS,
:: WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
:: See the License for the specific language governing permissions and
:: limitations under the License.

PATH=%PATH%;"%SYSTEMROOT%\System32"
fastboot oem unlock
fastboot erase boot
fastboot erase cache
fastboot erase recovery
fastboot erase system
fastboot erase userdata
fastboot flash bootloader bootloader-grouper-4.23.img
fastboot reboot-bootloader
ping -n 10 127.0.0.1 >nul
fastboot -w update image-nakasi-krt16s.zip

echo Press any key to exit...
pause >nul
exit

This installation script will totally wipe your device.
I've highlighted in orange the culprit of the wiping.

The first orange line "fastboot oem unlock" will unlock your device.
I removed this line because I know that my tablet is already unlocked.
I know that unlocking a locked tabled will wipe all user data.

The second orange line "fastboot erase userdata" will erase all user data, to my undestanding this mean deleting your data/image/music/apps. So I removed this line because I want to keep all my user data.

On the last line I've removed the "-w" from the update command, the -w parameter tell the update command to wipe your device. And I don't want to wipe my device.


Here is my modified "flash-all.bat" script

@ECHO OFF
:: Copyright 2012 The Android Open Source Project
::
:: Licensed under the Apache License, Version 2.0 (the "License");
:: you may not use this file except in compliance with the License.
:: You may obtain a copy of the License at
::
::      http://www.apache.org/licenses/LICENSE-2.0
::
:: Unless required by applicable law or agreed to in writing, software
:: distributed under the License is distributed on an "AS IS" BASIS,
:: WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
:: See the License for the specific language governing permissions and
:: limitations under the License.

PATH=%PATH%;"%SYSTEMROOT%\System32"
fastboot erase boot
fastboot erase cache
fastboot erase recovery
fastboot erase system
fastboot flash bootloader bootloader-grouper-4.23.img
fastboot reboot-bootloader
ping -n 10 127.0.0.1 >nul
fastboot update image-nakasi-krt16s.zip

echo Press any key to exit...
pause >nul
exit

You CAN'T copy/paste this script, because it include path/filename/command specific for my device factory image (Nexus 7 WiFi v2012 Android 4.4): You should instead edit the script included in the factory image file for you device!

 

KEEP IN MIND THAT I'M NOT AN ANDROID EXPERT.

THIS SCRIPT MAY BRICK YOUR DEVICE

To my understanding maybe this script will work for you if:

• you are doing a "small" upgrade, like from android 4.3 to android 4.4
• you device is already unlocked
• you know the meaning of the following words: adb, sdk, command prompt, bootloader, recovery, locked/unlocked device, flash, partition, cache, firmware, root, mod, rom, hack

 This script probably will not work if:

• you are doing a big upgrade, like from Android 4.3 to Android 5.0
• your device is locked

This script is modified to try to not wipe your data, so it's totally possible that it will leave some unneeded file somewhere on your tablet.
I dont know if future OTA update will work. Update: my tablet just received the OTA update to Android 4.4.2, and it worked! :-)

As of today, this modified script saved me a tons of work: now my Nexus 7 is once again up and running, on Android 4.4.
Now it's unrooted, maybe I will try to reroot it in future.

In case you need it, here is a link to the linux version of this script modified in the same way by James Finstrom: it seem he is the only one that did something similar.

Feel free to ask any question in the comments.

How to protect your Galaxy S4: UAG Case, Iloome Flex screen protector, ShockSock neoprene pouch, and some cardboard

Some month ago I bought my new smartphone: a Samsung Galaxy S4 (GT-I9505).
There are people that change their smartphone each year: there is nothing wrong with that, but I'm not one of those :-)
My previous phone was an HTC S620 (also know as HTC Excalibur) with Windows Mobile 5, then upgraded to WM 6.5.
I bought it in 2006, and kept it for 7 years.

I waited this much mainly because of my check list for my new smartphone:

• Quad core CPU
• 2GB of Ram
• 32GB of internal storage
• MicroSD
• Replaceable battery
• 5" FullHD screen
• AMOLED screen
• Decent camera
• Good community/hacking support

The Galaxy S4 checked all the points on my list, and when I found an online shop selling the 32Gb version at a reasonable price (580€), I bought it :-)

When I pay 580€ for a comput... ehm... a smartphone, I would like it to last some years, so I need to protect it.
A 5" full HD screen will shatter easily if dropped... and phone drops. My HTC s620 got dropped at least one time at year.

So, how do you protect a Samsung Galaxy S4?
After much researching, forum reading, reviews reading... I made the shopping list for protecting my S4:

• Case: UAG Navigator (Urban Armor Gear)
• Screen protector: Iloome Flex (flexible glass)
• Pouch: ShockSock neoprene pouch (size LG Optimus G Pro)
• and a piece of rigid cardboard

The case
Let's be honest: aesthetically speaking the Galaxy S4 isn't exactly the most beautiful smartphone.
But to me a smartphone is a tool to use, not something that need to be nice :-)
And I know that my phone will spend it's entire life inside it's case, so it doesn't matter if it's nice or not, I'll only see a touchscreen in a case.
As a case, I went for the Urban Armor Gear Navigator: It's fantastic!
It's very nice, it looks very cool, and have a very good finish.
 
Here are some photos of the S4 inside the Navigator.

Click the images to see them bigger

Now, some detail of the case so you can see the finish of the product.

The volume rocker, very comfortable to use.

 A detail of the volume rocker.

Here is the power button: I must say that the power button on the case is very comfortable to use.

The power button of the Galaxy S4 is ridiculously thin, its about 1mm x 1cm, ad I find it hard to press. With the case, instead, the power button became confortable to use.

 A detail of the external corner of the case

Here is the lower part, with the micro-USB connection, and the mike.

 This is one of the fake screw that are on the back of the case, very well done.

 And this is the UAG logo, on the back of the case.

On the back of the case there are these 4 tiny feet, and they are very useful feature because they accomplish 2 things:
the phone wont slip, and the white part of the phone will never touch the surface where the phone is resting, so it wont scratch easily.

 

The Screen Protector
I wen for the Iloome Flex (flexible glass) screen protector.
It's very thin (about 0,12mm) and it's compatible with the UAG Case.
Now I don't know if this is really glass, and I don't know if a real glass thick 0,12mm can be made flexible... but surely it seem to be more rigid and protective that the typical plastic-film screen protector.

Now some image of the installed screen protector.

Here is the home button, you can clearly see the very thin screen protector

Here you can see (from center to left) the button, the gorilla glass, the shadow of the screen protector border, and the screen protector. (click the image to see it gibber)

Here is the top part of the phone, the sensor and the camera are all covered by the screen protector: they seem to work without any issue.

 

 

Here you can see the screen protector and the top part of the case.
In my opinion, the screen protector go a bit under the case, but this doesn't seem to cause any issue, the UAG case fit perfectly on the phone with and without the Iloome Flex screen protector.
You can also see the shade of the screen protector.
I would like to pint out that the screen protector is perfectly adhering to the GS4 screen, but in these macro shot you still see the shadow of the border of the screen protector due to the thickness of the gorilla glass of the GS4.

Some other photos, done with natural light.

 

The Pouch
I don't feel right with a smartphone hanging around in my shoulder bag with an exposed screen, so I decided to buy a ShockSock neoprene pouch to give the phone a better protection.
I bought the pouch for the size of the LG Optimus G Pro, that is bigger than the GS4, because my S4 is bigger due to the UAG case.

Here are some photos of the pouch.

 And here you can see the size of the pouch respect the size of the Galaxy S4

The Cardboard
Now, I admit being a bit protective with this phone... :-)
I added a rigid piece of cardboard inside the pouch (I did the same in past for my Nexus 7, ad it worked well) just to give extra protection in front of the screen.
When the phone is hanging around in a shoulder bag between coins, home keys, car key, usb-pen drive, wallet, pen, post-it... the protection is never enough :-)

Here is the cardboard, I cut it out from the box of one of the last Christmas presents:-)
It's shaped in this way so that the GS4 wont get stuck when getting it and out from the pouch.

The cardboard are 2 pieces of rigid cardboard folded, and kepth this way with some scotch.
The total thickness is about 2m.

The cardboard is pretty rigid,  it doesn't flex under the weight of the GS4 :-)

The final result

And here you can see the final result from the top: Galaxy S4 inside UAG Case, The pouch, and the cardboard

Alternative Smartphone Case I tried
I used a Cygnett FlipFiber case  it's a very well done case, very slim, very nice to the touch. But it was not enough protective.
I bought an Otterbox Commuter from eBay for what seemed an honest price: don't do it, I've been ripped off, I received a fake Otterbox. If you want a genuine case, buy it directly form the manufacturer.
Anyway, after trying the fake otterbox I found out that the case design is very slippery, so I finally went for the UAG Navigator.

Alternative Screen protector
I pondered long time over which screen protector buy for my S4.
Spigen have many nice tempered glass screen protector for the S4, but I've not been able to find conclusive information abut the compatibility of Spigen screen protector with UAG Case.
So I finally went for the Iloome Flex, because I also liked the idea of having something a bit more flexible than a thin sheet of tempered glass in front of my S4.


Update: The Drop Test!
I can't believe it... one day after I wrote this post, and I dropped my GS4...
I was speaking at the phone, waiting in a queue at the supermarket.
I removed my scarf... and my S4 flied higher than my head, and then felt on the floor face down.
And it's still perfect! It doesn't have a scratch!
I picked up my phone and continued talking, it didn't even drop the call! :-)

The UAG Case + Iloome screen protector worked flawlessly! :-)

Feel free to ask any question in the comments :-)