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[Tutorial] How to backup mmcblk0 from a Qualcomm Android device - Printable Version

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How to backup mmcblk0 from a Qualcomm Android device - hovatek - 07-20-2018

This step-by-step guide will explain how to backup / extract mmcblk0 from a Qualcomm Android device using ADB.

Why would I need mmcblk0 for my Qualcomm device

In a situation where your Qualcomm device goes dead (not a battery or power issue) but still gets detected as QHSUSB_BULK or Qualcomm HS-USB QDLoader 9008 (depending on whether or not you have Qualcomm USB drivers installed) then the device is hard bricked. This is why it can only boot straight to Emergency Download (EDL) mode. In such a situation, an mmcblk0.img from a working phone of the same model would come in handy.


Steps to backup mmcblk0

Follow the steps below to extract mmcblk0 from a working Qualcomm device

See the video tutorial below or @ https://youtu.be/GZKzRyP2Vlk

  1. Launch ADB and run the following commands
    adb devicesadb shellsu
  2. On running the su command, you might get a prompt on the phone asking you to grant ADB Super User privileges, tap Grant
  3. Run this command in adb once $ changes to # in adb
    dd if=/dev/block/mmcblk0 of=/sdcard/mmcblk0.img
  4. Wait while the file is dumped to the phone storage
  5. Once backup is successful, you should get a message like
    7634944+0 records in7634944+0 records out3909091328 bytes (3.9 GB) copied, 3367.93 s, 1.2 MB/s

[Image: How-to-backup-mmcblk0-from-a-Qualcomm-An...device.png]

Important Notice
Some devices run into a loop when mmcblk0 is pulled to SD card so pull to your PC using
adb pull /dev/block/mmcblk0 mmcblk0.img
adb pull /dev/block/sda sda.img

Video Transcript
Quote:In this video tutorial, I'll be explaining how to extract or backup mmcblk0 from a Qualcomm Android device using ADB. You're going to need this file when your Qualcomm phone is hard bricked. Now, what do I mean by hard bricked? If your Qualcomm phone cannot boot up, yet when you connect it to a PC via a USB cord,  under Device Manager, You're going to have an entry like this;  QHSUSB_BULK (that's if you don't have Qualcomm drivers installed on your PC) or Qualcomm HS-USB QDLoader if you have Qualcomm drivers installed. Then, your device is hard bricked.

Now, the reason why device manager is detecting your device as this entry; yet, the phone cannot boot up is because your phone is booting straight to EDL Mode. EDL is Emergency Download mode so that means the phone is hard bricked and you need to flash the mmcblk0 to revive the phone. Now, to obtain the mmcblk0, you need to get access to a working phone of the same model.

You need to have rooted the phone. We have a guide on how to root. Then you need to have set up ADB. We also have a guide on how to set up ADB. Don't forget that you need to have enabled USB debugging on the phone for you to be able to use ADB on the working phone. Now, once you have all these in place, the next thing you want to do is to launch your ADB. Ideally, you launch ADB by holding Shift then clicking any blank space on the screen then selecting "Open Command Prompt here" but mine shows Power Shell so I have to go through a different approach to launch my ADB so I search for Command Prompt (CMD) and then I'm going to copy the address of my ADB folder and then I'm going to CD paste.

Alright, I've launched my ADB. I have my ADB all set up. Now, the next thing you want to do is to connect the Qualcomm device to the PC via a USB cord and then you're going to test the ADB connection. I'm going to type adb devices. Just to be sure ADB can detect. I have a detection. I'm going to now type adb shell don't forget, the phone should be rooted. Now, at this point, you should be taking a close look at your phone. Make sure you unlock it and you're looking at the screen.

Now, I'm going to request for Super User permission in ADB so I'm going to type su and then tap enter. Now, if its the first time you're running this su command, you're going to get a prompt on your device asking you to grant ADB Super User permission so what you want to do is to grant. I already did that so I'm not getting prompted again. Now, once you grant ADB Super User permission, $ should change to # this alright? The dollar sign should change  to the hash sign.

Now what you're going to do is to run this command. This is how the command goes dd if=/dev/block/mmcblk0 of=/sdcard/mmcblk0.img "mmcblk0" is the partition we want to backup. "of" specifies where we want to save to [inputting command] Now, what this command is basically doing is that its backing up this partition to the phone's storage and naming it as this mmcblk0.img so make sure you have enough storage on the phone which you want to backup mmcblk0 to.

I usually advise maybe 16GB+ depending on the kind of Qualcomm device you're dealing with. Although it shouldn't be that large, just make sure you have enough space on the phone storage. Now, once you have this command typed out, what you want to do is to tap Enter then wait while the mmcblk0 is being backed up to the device.

Now, you might have something like...mine is being backed..OK it's not being detected here. I have to actually connect to the phone. I have to actually check from the phone directly but on the phone here, I can see that mmcblk0 is now being backed up to the root of the phone storage.

Alright, so its actually quite a large file so you'll want to be patient. Do not interrupt this process okay? Once the backup is done, you're going to get a prompt telling you that the backup was successful. Once that is finished. You might want to disconnect and then copy the mmcblk0 to your desktop PC where you can restore it to the hard bricked Qualcomm device.

That's how to extract or backup mmcblk0  from a Qualcomm Android device using ADB