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Help Rooted and flashed LG G8 how do I backup the current firmware, flash a stock one and relock the bootloader

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vector3156

Newbie
I want to flash stock LG firmware on LG G8 (LM-G820UM). I would first like to backup what is currently on the phone, just in case I want to play around with it in the future. I also want to lock the bootloader again. Could someone please point me in the right direction? How do I backup the firmware the phone currently has? When I search for firmware how do I find out what firmware do I need, which one should I choose and from where should I get it from? How do I flash firmware on LG phones? How do I make sure I have done everything correctly so the phone doesn't become a brick and how do I lock the bootloader again? Do I also need to flash any rom/s? I don't have much experienced flashing phones. Any help is appreciated :).
 
ocnbrze said:
use adb commands to lock the bootloader:

Lock and unlock the bootloader | Android Open Source Project

source.android.com source.android.com

just curious as to why you want to unroot?

as far as backing up, doesn't lg have their own utility program that you can use to backup your phone? i have never owned a lg phone.
Click to expand...
The phone was behaving strange (battery dropped by like 6-8%, and I couldn't swipe down for the drop down menu and only the back button worked), now it seems fine but I'm worried something might be up, as someone before me has rooted it and I don't know what they might have done to it. I can't know if something malicious has been installed.
 
ok i see. yeah if you bought the phone used and it is rooted, i would be worried about security issues.....so i understand that.
however you can always just flash a different custom rom, if you wanted to stay rooted. it wipes everything clean. there is an app called titanium backup that allows you to backup your apps and data. but it only works on rooted phones.

if you want to do that then we can help you with that. if you are uncomfortable with having a rooted phone we can also help you unroot it. the problem is that i never had a lg phone. and there is not really an official source to get firmware(stock rom) for lg phones that i know of. there are plenty of sites offering them if you google it, but i do not know how legit it is,

i did find this on xda which is your best source for all things root related:
xdaforums.com

LG G8 LMG820UM AT&T STOCK FIRMWARE/KERNEL

Hello, could someone PLEASE provide me with a stock or source for stock firmware for the AT&T LG G8 Thinq (LMG820UM). I've looked everywhere and can only find the U.S. Cellular, Verizon, Sprint, and T-mobile versions (everything except what I...
xdaforums.com xdaforums.com

and i found this from a quick google search:
lg-firmwares.com

LG G820UM(LMG820UM) aka LG G8 ThinQ - LG-Firmwares.com

LMG820UM download the firmware for free! Detailed installation instruction. Video review of the model and its features. User feedback and latest news.
lg-firmwares.com lg-firmwares.com
 
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ocnbrze said:
ok i see. yeah if you bought the phone used and it is rooted, i would be worried about security issues.....so i understand that.
however you can always just flash a different custom rom, if you wanted to stay rooted. it wipes everything clean. there is an app called titanium backup that allows you to backup your apps and data. but it only works on rooted phones.

if you want to do that then we can help you with that. if you are uncomfortable with having a rooted phone we can also help you unroot it. the problem is that i never had a lg phone. and there is not really an official source to get firmware(stock rom) for lg phones that i know of. there are plenty of sites offering them if you google it, but i do not know how legit it is,

i did find this on xda which is your best source for all things root related:
xdaforums.com

LG G8 LMG820UM AT&T STOCK FIRMWARE/KERNEL

Hello, could someone PLEASE provide me with a stock or source for stock firmware for the AT&T LG G8 Thinq (LMG820UM). I've looked everywhere and can only find the U.S. Cellular, Verizon, Sprint, and T-mobile versions (everything except what I...
xdaforums.com xdaforums.com

and i found this from a quick google search:
lg-firmwares.com

LG G820UM(LMG820UM) aka LG G8 ThinQ - LG-Firmwares.com

LMG820UM download the firmware for free! Detailed installation instruction. Video review of the model and its features. User feedback and latest news.
lg-firmwares.com lg-firmwares.com
Click to expand...
To lock the bootloader I first have to flash the original firmware the phone had, correct? I asked on XDA for information on firmware and locked/unlocked bootloader and this is what I was told. Since I plan on using the phone as my daily driver I don't think it's a good idea for it to stay rooted. But I don't know, what do you think should I leave it rooted? I don't go around clicking every dodgy download button I see. As for the links you provided I did see them but I'm not sure how legit that website for the firmware is, I also want to gather as much information as I can, before I attempt to do this, as I very much like this phone and want to use it. I don't want to mess it up and turn it into a brick. At the moment it works but im worried that there might be something malicious and I can't check or know for sure.
 
OK so this app called magisk manager wanted to update and I decided to download and install the update, it then wanted to restart but before the restart it said something about how it shouldn't be running as an app, that its not supported and should be running as a user app, the phone restarted and proceeded to bootloop. I was able to factory reset the phone in the recovery. I don't think this phone should have such recovery menu but it does. After that I tried to remove the magisk manager and it gives me two options: restore images and complete uninstall. Pressing on "restore images" gives a message "stock backup does not exist!" and pressing "complete uninstall" doesn't do anything. Also the battery went from 39 or so percent to 13 after one of the reboots I did. Something is wrong here. Maybe this firmware is not worth backing up.
 

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ok so what is odd is that the previous owner rooted the phone but never installed a custom recovery. that image is of the stock recovery, what you did is called a hard reset vs a factory reset. you should just uninstall magisk app from the phone. were you able to find a stock rom for your phone?
 
ocnbrze said:
ok so what is odd is that the previous owner rooted the phone but never installed a custom recovery. that image is of the stock recovery, what you did is called a hard reset vs a factory reset. you should just uninstall magisk app from the phone. were you able to find a stock rom for your phone?
Click to expand...
I will download one from this website: LG G820UM(LMG820UM) aka LG G8 ThinQ - LG-Firmwares.com (looks to be the most legit one), but I'm not sure which one. I can't uninstall the magisk manager app it only has disable option and the app itself is complaining it is being ran as a system app. Can't confirm 100% what carrier the phone was also on. On gsm arena it appears to be Sprint.
 
vector3156 said:
I will download one from this website: LG G820UM(LMG820UM) aka LG G8 ThinQ - LG-Firmwares.com (looks to be the most legit one), but I'm not sure which one. I can't uninstall the magisk manager app it only has disable option and the app itself is complaining it is being ran as a system app. Can't confirm 100% what carrier the phone was also on. On gsm arena it appears to be Sprint.
Click to expand...
Is that your provider? Sprint?
 
ocnbrze said:
Is that your provider? Sprint?
Click to expand...
No, I live in Europe. I wanted to find out because I was told the firmware has to be original to relock the bootloader and since I'm not sure if I can use for example Korean stock firmware for a G8 to lock it again I wanted to find out what carrier the phone is from and try to track down that exact firmware.
 
vector3156 said:
No, I live in Europe. I wanted to find out because I was told the firmware has to be original to relock the bootloader and since I'm not sure if I can use for example Korean stock firmware for a G8 to lock it again I wanted to find out what carrier the phone is from and try to track down that exact firmware.
Click to expand...
no.....firmwares are very device specific. go into your phone settings>about phone>and look for your model number. do a search for firmware for the model number.
 
ocnbrze said:
no.....firmwares are very device specific. go into your phone settings>about phone>and look for your model number. do a search for firmware for the model number.
Click to expand...
Its LM-G820UM in the settings and on the box. In gsm arena they have all versions listed, with the closest matching being LM-G820UM0 and it being Sprint. But I have just seen an AT&T G8 with LM-G820UM written the label on the back, so it could be any other USA carrier. That has me thinking if its possible to fake phone model and IMEI in the settings? The label on the box has the letters "SPR", wonder if that means Sprint?
 
ocnbrze said:
maybe try this one:
lgstockrom.com

LG G8 ThinQ LMG820UM Stock ROM Firmware (Flash File)

Download the official LG G8 ThinQ LMG820UM Stock ROM Firmware (Flash File) for your device. We also provide Stock ROM for other LG devices.
lgstockrom.com lgstockrom.com
Click to expand...
None of the downloads work on that website. I cant figure out how to flash it. I cant get the phone in download mode as most guides instruct me to do. All I can get to is recovery mode and even then LGUP doesn't recognize the phone, it detects that a phone is connected but it can't recognize it. LGUP with cmd doesn't open at all on my pc. LG flash tool I can't figure out how to work with. I don't know if I can try to flash with an SD card no matter how much I search I cant find how to prepare the SD card or if its even possible to do it. ADB sideload I also cant figure out. Basically wasted a lot of time for nothing. Any suggestions?
 
vector3156 said:
None of the downloads work on that website. I cant figure out how to flash it. I cant get the phone in download mode as most guides instruct me to do. All I can get to is recovery mode and even then LGUP doesn't recognize the phone, it detects that a phone is connected but it can't recognize it. LGUP with cmd doesn't open at all on my pc. LG flash tool I can't figure out how to work with. I don't know if I can try to flash with an SD card no matter how much I search I cant find how to prepare the SD card or if its even possible to do it. ADB sideload I also cant figure out. Basically wasted a lot of time for nothing. Any suggestions?
Click to expand...
ttry using the mirror 2 on the first one. it takes you to a different file sharing site. you should be able to download the file.
 
vector3156 said:
Its LM-G820UM in the settings and on the box. In gsm arena they have all versions listed, with the closest matching being LM-G820UM0 and it being Sprint. But I have just seen an AT&T G8 with LM-G820UM written the label on the back, so it could be any other USA carrier. That has me thinking if its possible to fake phone model and IMEI in the settings? The label on the box has the letters "SPR", wonder if that means Sprint?
Click to expand...
i would take down the picture........you never want to show your imei. that is very specific to your phone. bad people can use imei and spoof phones with it.....i'll alert the mods if you can't delete the photo.
 
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