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[LG Velvet 4G | LMG910EMW] A noobs guide for installing Magisk (rooting), SafetyNet, Gcam buffer fix and fingerprint fix

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GerRudi

Senior Member
Mar 1, 2015
56
11
Disclaimer: None of this is my work! I only used guides from other people and decided to create single a step-by-step guide for the LG Velvet (4G version). I tried crediting all people at the end of the post.
I am not responsible if you brick your device - use this guide at your own risk and know what you are doing.
After unlocking, your fingerprint reader will no longer work, this can be fixed and the instructions can be found below.

All these tools are commandline tools (cmd) - you should know how to use them.
You should also be familiar with "adb" and "fastboot".
This is not a guide for noobs, only a guide made by a noob.
Unless mentioned otherwise, all these steps are to be done on your computer.
I used Windows 10, it should work on other platforms just fine with a few modifications.

Bootloader Unlock
(European Version - I have no idea about the possibilities of unlocking provider-locked phones or other regions!!!)

Create an account and follow the instructions here:
https://developer.lge.com/resource/mobile/RetrieveBootloader.dev

The steps are explained quite well, therefore I will not write them down here unless people actually have problems with the steps.
(Preparation on the phone: Enable developer options, allow USB debugging and allow OEM Unlock.)
As always, unlocking the bootloader will WIPE your phone.

Installing Magisk / Systemless root
(After you successfully unlocked the bootloader, remember to re-enable developer options on the phone and allow USB Debugging)


Download the latest firmware here.
Use the IMEI search if you don't know which one you need!

Using this page, you will eventually receive a link ending in .kdz.
I don't recommend using the Download tool provided by lg-roms, but instead this script:
https://forum.xda-developers.com/t/...nd-lgup_ui-fixer.3916444/page-2#post-84148225

Paste the .kdz URL in the tool and wait for the Download to complete.


Next, you will need a copy of kdztools. Download a copy of this repository.
Important: Do not download from "Releases" - they are outdated! Instead, download a copy of the current master branch!

To be able to use this tool, you need to have python3 installed.
I will not further describe this step as there are enough tutorials out there and it is usually self explanatory.
You will have to install the module "zstandard" for the script to work:
pip3 install zstandard


Use KDZ Tools together with the downloaded firmware.
First, exctrat the KDZ file:
python unkdz.py -f G910EMW10i_00_0520.kdz -x

You should now have a large .dz file in the subfolder "kdzextracted". We can use this file to extract the boot image:
python undz.py -f c:G91010i_00_user-signed-ARB0_COM1_EU_OP_0520.dz -s 41
After this step, you should have a file "boot_a.image" in the subfolder "dzextracted".
(If you received a different file, use "python undz.py -f c:G91010i_00_user-signed-ARB0_COM1_EU_OP_0520.dz --list" and search for the partition named boot, edit the number "41" in the previous command accordingly)

Rename the boot_a.image to "boot.img" and copy it to your phone.
Download and install the latest Magisk release on your LG device.

In Magisk, select Install and patch the boot.img file.

After patching, copy the patched Magisk image back to your computer, rename it for easier use.


Using adb/fastboot on your pc:

adb reboot bootloader
fastboot flash boot_a magisk.img
fastboot flash boot_b magisk.img

Finally

Wait for the phone to boot and check Magisk installation status.

Congratulations!

Disable automatic firmware updates on your phone if you want to avoid having to re-install a patched Magisk image after every update!


Passing SafetyNet (Google Pay and more)
(You might not need all steps - after every step, you can check SafetyNet status via Magisk and if it is still broken, continue with the next step.)

Reboot after every step!
  1. In the Magisk App, open Settings (top right) and enable the option "MagiskHide"
  2. Download Universal safetynet fix and manually add as a module in the Magisk app
  3. Download Magisk Hide Props Conf (manual DL not needed, can be found as a module directly in the app)
  4. Unless there was an update to SafetyNet, you should now be able to set up and use SafetyNet services like Google Pay
Fixing your fingerprint reader
After the bootloader unlock, you will no longer be able to register fingerprints. This can be fixed using the following steps:
  1. Launch the hidden service menu by dialing #*462633*#910# (might require an inserted SIM card)
  2. SVC Menu -> Handprint -> HandID Logging "ON"
  3. Go to the start of the menu and then navigate to "Device Test" -> SAAT -> Manual Test -> Optical FingerPrint Test
  4. Press SEVERAL times firmly on the green button until it says FAILED, confirm and exit the menu
  5. Go to settings and set up your fingerprints!
  6. AFAIK, you can now disable "HandID Logging" again


Gcam Buffer Fix (Viewfinder Lag)
Using Gcam on the LG Velvet 4G, you will notice that most of the ports will not work properly.
Only a few versions based on Gcam 6.x with the option "buffer fix" will somewhat work, but not very well.

If you have Magisk installed, you can install the
Buffer Fix that was originally designed for the LG V40 (Use the one for Android 10). Just flash the ZIP as a Magisk module.
Some Gcams will crash but MGC builds by BSG appear to work well!
(I don't know how this buffer fix works so I don't know if it is healthy to flash a module that was designed for a different phone but I tried several bufferfixes for different phones and this one appears to work flawless.)




Credits:
The very good rooting guide for the LG Velvet 5G by MikGX - THANK YOU
https://forum.xda-developers.com/t/root-lg-velvet-lm-g900em.4171117/

KDZ Download Tool by CXZa

SafetyNet Fix by kdrag0n

MagiskHide Props Conf by Didgeridoohan

Buffer fix for LG V40 by Wyroczen.

Fingerprint fix instructions provided by raj_ch2002 for the LG G8X

(Linked by foggydew88 here) - thanks!

paolotheking for providing the LG Velvet 5g service menu code, which is similar to this model

Finally, thanks to the devs of Magisk, kdztools and lg-roms
 
Last edited:
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orinoco.op.pl

New member
Aug 2, 2021
2
0

EmanuelCN

Senior Member
Mar 29, 2017
292
93
LG G7 ThinQ
Xiaomi Poco F3
Can someone from 20a backup me system and vendor partitions ? Not the ones from kdz, i need as they are in the phone with partition backup app that requires root either with qfil? i can give instructions just dm me on telegram @EmanuelCN0 . I specifically need from EMW model.
 

Chick0Nugget

New member
Aug 28, 2021
2
0
Got the German Version of the phone (DEA) ... Everytime i want to use undz.py it says Error: extraneous data found IN version. Also unkdz.py says something but extracts the .dz. Any idea what i could do ?
 

swaguduzo

Member
Sep 21, 2019
25
4
Hello. I've succesfully rooted my European Velvet LTE/4G variant.

Most of the kdz extractors are a total disaster and won't work with recent KDZs. You have to use this one:


This is the correct, working KDZ extractor. Save this raw Python script for example as a kdz_extractor.py.

Now, assuming you already have performed the previous necessary steps like installing zstandard with pip, all you have to do is:

python3 kdz_extractor.py -e <where to extract> <kdz to extract>


You'll have a file called 4.boot_a.img, around 96 MBs. Now you can keep following the OP guide.
I can provide the patched boot_a.img for LMG910EMW Android 11 20a version if someone needs it.
 

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    Disclaimer: None of this is my work! I only used guides from other people and decided to create single a step-by-step guide for the LG Velvet (4G version). I tried crediting all people at the end of the post.
    I am not responsible if you brick your device - use this guide at your own risk and know what you are doing.
    After unlocking, your fingerprint reader will no longer work, this can be fixed and the instructions can be found below.

    All these tools are commandline tools (cmd) - you should know how to use them.
    You should also be familiar with "adb" and "fastboot".
    This is not a guide for noobs, only a guide made by a noob.
    Unless mentioned otherwise, all these steps are to be done on your computer.
    I used Windows 10, it should work on other platforms just fine with a few modifications.

    Bootloader Unlock
    (European Version - I have no idea about the possibilities of unlocking provider-locked phones or other regions!!!)

    Create an account and follow the instructions here:
    https://developer.lge.com/resource/mobile/RetrieveBootloader.dev

    The steps are explained quite well, therefore I will not write them down here unless people actually have problems with the steps.
    (Preparation on the phone: Enable developer options, allow USB debugging and allow OEM Unlock.)
    As always, unlocking the bootloader will WIPE your phone.

    Installing Magisk / Systemless root
    (After you successfully unlocked the bootloader, remember to re-enable developer options on the phone and allow USB Debugging)


    Download the latest firmware here.
    Use the IMEI search if you don't know which one you need!

    Using this page, you will eventually receive a link ending in .kdz.
    I don't recommend using the Download tool provided by lg-roms, but instead this script:
    https://forum.xda-developers.com/t/...nd-lgup_ui-fixer.3916444/page-2#post-84148225

    Paste the .kdz URL in the tool and wait for the Download to complete.


    Next, you will need a copy of kdztools. Download a copy of this repository.
    Important: Do not download from "Releases" - they are outdated! Instead, download a copy of the current master branch!

    To be able to use this tool, you need to have python3 installed.
    I will not further describe this step as there are enough tutorials out there and it is usually self explanatory.
    You will have to install the module "zstandard" for the script to work:
    pip3 install zstandard


    Use KDZ Tools together with the downloaded firmware.
    First, exctrat the KDZ file:
    python unkdz.py -f G910EMW10i_00_0520.kdz -x

    You should now have a large .dz file in the subfolder "kdzextracted". We can use this file to extract the boot image:
    python undz.py -f c:G91010i_00_user-signed-ARB0_COM1_EU_OP_0520.dz -s 41
    After this step, you should have a file "boot_a.image" in the subfolder "dzextracted".
    (If you received a different file, use "python undz.py -f c:G91010i_00_user-signed-ARB0_COM1_EU_OP_0520.dz --list" and search for the partition named boot, edit the number "41" in the previous command accordingly)

    Rename the boot_a.image to "boot.img" and copy it to your phone.
    Download and install the latest Magisk release on your LG device.

    In Magisk, select Install and patch the boot.img file.

    After patching, copy the patched Magisk image back to your computer, rename it for easier use.


    Using adb/fastboot on your pc:

    adb reboot bootloader
    fastboot flash boot_a magisk.img
    fastboot flash boot_b magisk.img

    Finally

    Wait for the phone to boot and check Magisk installation status.

    Congratulations!

    Disable automatic firmware updates on your phone if you want to avoid having to re-install a patched Magisk image after every update!


    Passing SafetyNet (Google Pay and more)
    (You might not need all steps - after every step, you can check SafetyNet status via Magisk and if it is still broken, continue with the next step.)

    Reboot after every step!
    1. In the Magisk App, open Settings (top right) and enable the option "MagiskHide"
    2. Download Universal safetynet fix and manually add as a module in the Magisk app
    3. Download Magisk Hide Props Conf (manual DL not needed, can be found as a module directly in the app)
    4. Unless there was an update to SafetyNet, you should now be able to set up and use SafetyNet services like Google Pay
    Fixing your fingerprint reader
    After the bootloader unlock, you will no longer be able to register fingerprints. This can be fixed using the following steps:
    1. Launch the hidden service menu by dialing #*462633*#910# (might require an inserted SIM card)
    2. SVC Menu -> Handprint -> HandID Logging "ON"
    3. Go to the start of the menu and then navigate to "Device Test" -> SAAT -> Manual Test -> Optical FingerPrint Test
    4. Press SEVERAL times firmly on the green button until it says FAILED, confirm and exit the menu
    5. Go to settings and set up your fingerprints!
    6. AFAIK, you can now disable "HandID Logging" again


    Gcam Buffer Fix (Viewfinder Lag)
    Using Gcam on the LG Velvet 4G, you will notice that most of the ports will not work properly.
    Only a few versions based on Gcam 6.x with the option "buffer fix" will somewhat work, but not very well.

    If you have Magisk installed, you can install the
    Buffer Fix that was originally designed for the LG V40 (Use the one for Android 10). Just flash the ZIP as a Magisk module.
    Some Gcams will crash but MGC builds by BSG appear to work well!
    (I don't know how this buffer fix works so I don't know if it is healthy to flash a module that was designed for a different phone but I tried several bufferfixes for different phones and this one appears to work flawless.)




    Credits:
    The very good rooting guide for the LG Velvet 5G by MikGX - THANK YOU
    https://forum.xda-developers.com/t/root-lg-velvet-lm-g900em.4171117/

    KDZ Download Tool by CXZa

    SafetyNet Fix by kdrag0n

    MagiskHide Props Conf by Didgeridoohan

    Buffer fix for LG V40 by Wyroczen.

    Fingerprint fix instructions provided by raj_ch2002 for the LG G8X

    (Linked by foggydew88 here) - thanks!

    paolotheking for providing the LG Velvet 5g service menu code, which is similar to this model

    Finally, thanks to the devs of Magisk, kdztools and lg-roms