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[GUIDE-IMPORTANT!] "rescue-backdoor" - regarding bootloop, do it before change in sys

OP condi

21st February 2012, 03:24 PM   |  #1  
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UPDATE: THIS IS OBSOLETE.
USE S.onyTablet.S [ALLinONE] tool
Below guide/tool use as 'description'

-------------------------------------------------------------------------

Hi guys,



We've got now ROOT. We can do a lot of things, which we couldn't do before.
But before you begin to make changes in system files, first you need to know few things.

Few users experienced "bootloop". Its brick state. There is no access to shell, no adb.
Damaged device.

How to avoid that?

Yes, there is a solution. We need to get proper update zip for our device.
We also need to fool device, that it is a newer file, than the firmware in device.

How to, step by step:
  1. Of course, ROOT is required.
  2. To get proper ota-update-zip for your device you have to edit /build.prop:
    - easiest way is via "Root Explorer", or directly via "build.prop Editor" (in market, free),
    - do not use "File Manager HD" or other filemanager, which doesn't support root operations (thx kryddan),
    - always make backup of files, which you are modifying,
    - change value of "ro.sony.build.incremental" to lower one to fake firmware version,
    - for example on my device newest firmware has: "ro.sony.build.incremental=111201022" - decrease that value,
    in my case to 111201021.
  3. Reboot device.
  4. OTA update notification will appear - click on "Download" button.
  5. Wait until download finishes, but don't click "Update"!!!
    I repeat - DON'T CLICK UPDATE! It will reflash firmware,
    and you will have to make everything from the beginning (inc. root).
  6. Update zip is located in /cache/ota/signed-nbx03_.......zip - make a copy to safe place - external sd and/or in pc.
  7. Leave build.prop modified. IMPORTANT. Don't revert back changes.

To enter RECOVERY-MODE - power off device,
hold vol-down + power button.

When you want to flash your device, Sony Tablet is checking few things:
  • is update zip proper one - signed one,
  • is the update zip - for your region - SKU value,
  • is the update zip is newer one than firmware in device - equal and higher will not update,
    only lower - thats what we're faking.

If you will revert back build.prop = update will fail,
if you will try to update with other region update zip = update fail.

So if we stay with modified build.prop = we can just enter recovery,
and update from external sd card, to our downloaded update zip

Remember, that after reflash in recovery, your build.prop will be updated back
to higher value, then to be safe you need to reapply modification!


I have tested that "rescue-backdoor" on my own device,
deleted some system framework file - of course bootloop, without adb access.
Flashed through recovery - voila, device fixed

Of course, everything what you do with your device, you are doing at your own
risk. I'm sure that in 99% cases with "rescue-backdoor" you will fix your device,
always could be that other 0,01% case.

One condition for sure = build.prop file has to be correct.


[OPTIONAL]
You can disable ota update notification - which appears on every reboot.
To do this use "Titanium Backup" app, look for "System Update" app on list,
and use "Freeze" option



Any questions, suggestions - just ask

PS. I'm thining about writing auto-script for that...


br
condi
Last edited by condi; 25th February 2012 at 04:08 PM.
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21st February 2012, 06:23 PM   |  #2  
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great guide, thank you

I think an automated-script would be much appreciated
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21st February 2012, 06:42 PM   |  #3  
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Quote:
Originally Posted by condi

Hi guys,



We've got now ROOT. We can do a lot of things, which we couldn't do before.
But before you begin to make changes in system files, first you need to know few things.

Few users experienced "bootloop". Its brick state. There is no access to shell, no adb.
Damaged device.

How to avoid that?

Yes, there is a solution. We need to get proper update zip for our device.
We also need to fool device, that it is a newer file, than the firmware in device.

How to, step by step:

  1. Of course, ROOT is required.
  2. To get proper ota-update-zip for your device you have to edit /build.prop:
    - easiest way is via "Root Explorer", or directly via "build.prop Editor" (in market, free),
    - always make backup of files, which you are modifying,
    - change value of "ro.sony.build.incremental" to lower one to fake firmware version,
    - for example on my device newest firmware has: "ro.sony.build.incremental=111201022" - decrease that value,
    in my case to 111201021.
  3. Reboot device.
  4. OTA update notification will appear - click on "Download" button.
  5. Wait until download finishes, but don't click "Update"!!!
    I repeat - DON'T CLICK UPDATE! It will reflash firmware,
    and you will have to make everything from the beginning (inc. root).
  6. Update zip is located in /cache/ota/signed-nbx03_.......zip - make a copy to safe place - external sd and/or in pc.
  7. Leave build.prop modified. IMPORTANT. Don't revert back changes.

When you want to flash your device, Sony Tablet is checking few things:
  • is update zip proper one - signed one,
  • is the update zip - for your region - SKU value,
  • is the update zip is newer one than firmware in device - equal and higher will not update,
    only lower - thats what we're faking.

If you will revert back build.prop = update will fail,
if you will try to update with other region update zip = update fail.

So if we stay with modified build.prop = we can just enter recovery,
and update from external sd card, to our downloaded update zip

I have tested that "rescue-backdoor" on my own device,
deleted some system framework file - of course bootloop, without adb access.
Flashed through recovery - voila, device fixed

Of course, everything what you do with your device, you are doing at your own
risk. I'm sure that in 99% cases with "rescue-backdoor" you will fix your device,
always could be that other 0,01% case.

One condition for sure = build.prop file has to be correct.


[OPTIONAL]
You can disable ota update notification - which appears on every reboot.
To do this use "Titanium Backup" app, look for "System Update" app on list,
and use "Freeze" option



Any questions, suggestions - just ask

PS. I'm thining about writing auto-script for that...


br
condi

Thanks Condi! Download worked great but under my cache there is nothing. Could the file be located elsewhere?
21st February 2012, 06:59 PM   |  #4  
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It should be under '/cache/ota' ... nowhere else ..
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21st February 2012, 07:06 PM   |  #5  
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Quote:
Originally Posted by Judah001

Thanks Condi! Download worked great but under my cache there is nothing. Could the file be located elsewhere?

Be sure that ota has been download, check again /cache/ota.
If still no zip, then run 'adb shell' then:
Code:
su
find -name *signed*
or
Code:
find -name *.zip
If your ota update will be in different location, then please post it.

br
condi
21st February 2012, 07:15 PM   |  #6  
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Quote:
Originally Posted by condi

Be sure that ota has been download, check again /cache/ota.
If still no zip, then run 'adb shell' then:

Code:
su
find -name *signed*
or
Code:
find -name *.zip
If your ota update will be in different location, then please post it.

br
condi

ok I will try once I am home through adb. So far there is nothing under my cache folder. I am using file manager HD but it should pick up a zip file.
21st February 2012, 07:21 PM   |  #7  
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Thank you condi... The instructions worked perfectly!!
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21st February 2012, 07:21 PM   |  #8  
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Quote:
Originally Posted by Judah001

ok I will try once I am home through adb. So far there is nothing under my cache folder. I am using file manager HD but it should pick up a zip file.

Just a little tip. I'd suggest you use Root Explorer instead of File Manager HD.
You see, File Manager HD does not show the files in /cache. (mine didn't)

I tried File Manager HD on my tablet and found nothing inside /cache
But with Root Explorer I found three different directories. There among OTA.
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21st February 2012, 07:36 PM   |  #9  
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Quote:
Originally Posted by kryddan

Just a little tip. I'd suggest you use Root Explorer instead of File Manager HD.
You see, File Manager HD does not show the files in /cache. (mine didn't)

I tried File Manager HD on my tablet and found nothing inside /cache
But with Root Explorer I found three different directories. There among OTA.

That did the trick. I used the root browser in rom tool box and copied the zip to my sd card. Thank you for the help guys.
21st February 2012, 07:41 PM   |  #10  
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Good advice kyddan ... same on my tab with file manager HD.
I work normally with Root Explorer or File Expert.
Both show the folders and files in /cache .. File Manager HD do not.

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