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[[GUIDE]] Flashing Custom GSI ROM to LG G8 (LG820UMx)

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SirOlive

Member
Apr 13, 2021
5
1
LG G8
Moto G Stylus 5G
This might be completely unnecessary (mods feel free to remove if it is), but I see a LOT of misinformation regarding GSI ROMs and the G8. So. Here's a guide/FAQ for those wondering if/what is possible:

***I'M NOT RESPONSIBLE IF YOU BRICK YOUR PHONE, LOSE YOUR DATA, OR OTHERWISE DAMAGE YOUR DEVICE. IF YOU CHOOSE TO FOLLOW THIS GUIDE, THE FATE OF YOUR DEVICE IS IN YOUR HANDS, NOT MINE, NOT YOUR MOTHER'S, NOT ANYONE OTHER THAN YOUR OWN***

Prerequisites (yes, these are all NECESSARY. If you don't know how to unlock your bootloader or use fastboot, there are other guides here. Go find one.)
  • Unlocked bootloader (and the V50 engineering abl files as well as stock, plenty of guides here with download links)
  • QFIL/QPST
  • Basic Fastboot, ADB knowledge
  • BACKUP. I mean ALL YOUR DATA kinda backup. This WILL wipe your phone, do NOT come crying to me if you lose the last picture of your favorite sock. Not my fault.
  • GSI for Treble device (ab)
  • GApps (optional, but recommended)

Instructions to Flash via Fastboot
  • WIPE YOUR PHONE
    • Yeah, completely factory reset that sucker. Doesn't matter if it's through recovery, settings, or adb, just bite the bullet and restore factory settings. You can technicially flash without doing this first, but you'll still have to wipe it before any flashed ROM will run. Sorry.
  • Boot to EDL (NOT download, your screen should be black, dev manager should show QD Loader 9008 COMx)
  • Use QFIL to flash engineering abl file to both a and b slots - yes, all this work just for fastboot.
  • Reboot to fastboot!
    • I just unplug my phone, use power + vol- to shut phone off and then reconnect while holding vol-, but you do you.
    • In case you don't remember, your touch screen WILL NOT WORK during this time, even if you fully boot to system! Completely fine and normal, means you're on the right track!
    • Fastboot Devices should yield "LG850UM", also good!
  • Open cmd prompt from platform_tools, copy path to desired GSI while you're in there
  • Run these commands line-by-line:
    • fastboot format system
    • fastboot flash system *Path_To_GSI.img*
      • This is where I usually repeat the 2 commands and attempt reboot while I still have fastboot, whether or not it changes anything I have no idea, but it's never given me problems so why fix it if it ain't broke?
    • fastboot flash abl_a abl_STOCK.bin
    • fastboot flash abl_b abl_STOCK.bin
    • fastboot reboot
  • Ta-Da! Your shiny new ROM should be up and running. Use TWRP or any kernel manager (I like SmartPak) to flash TWRP, GApps, blah blah blah.

FAQ/Troubleshooting
  • Touchscreen still not working? Go back to EDL and load the stock abl bin files through QFIL, then reboot as normal.
  • You will likely be asked to input a password upon successful reboot, just enter your PIN/password, whatever you used to unlock your phone pre-flash
  • The cool things like QuadDAC and LG-specific tweaks will probably not work. Weigh your options before flashing.
  • Magisk comes pre-installed with most GSI's, just follow the prompts and you'll be just fine.
  • Don't want GApps? Just sideload desired apk's via ADB, or use the browser to search for them.
  • Can't I just use TWRP and make this whole process a lot simpler? Yep. But some of us don't have working TWRP or prefer using fastboot commands. This is for those people, don't hate.
  • Which ROMs work?? Not sure, haven't tried them all. Currently running HavocOS found in Treble GSI forum on here.
  • Help! I broke my phone! No, you probably didn't. It's advisable that you know how to emergency restore via LGUP prior to starting this process though. Please be specific as to what part of this "broke" your phone and why exactly your phone is "broken" if you're going to ask for help- "bricked device" has never helped anyone.
  • Rebooting is your best friend in this process, especially during the first boot. If anything starts to hang up or act funny, just give the phone a minute to catch its breath and, worst case, turn it off and back on again

As previously stated, this is probably pointless, but given all I see on the G8 forum is "no custom ROM" or "why bother trying to *insert idea here*", I figured it might help some folks out. I'm sure I left a few things out, feel free to correct or provide input as necessary.
 
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AsItLies

Senior Member
Nov 4, 2009
1,358
528
tucson
Google Pixel 3
Great info, thnx for the write up. But what about the totc.cfg file? My understanding is no G8 is going to boot if there's a mis-match between that file and the hardware indication of what variant the phone is?

Sorry if my understanding is misguided, new to the G8 (and all it's idiosyncrasies).
 

SirOlive

Member
Apr 13, 2021
5
1
LG G8
Moto G Stylus 5G
Great info, thnx for the write up. But what about the totc.cfg file? My understanding is no G8 is going to boot if there's a mis-match between that file and the hardware indication of what variant the phone is?

Sorry if my understanding is misguided, new to the G8 (and all it's idiosyncrasies).
In this case there is no tot file, no recovery, laf, or the like. GSI's are generic system images that are capable of being flashed to most Treble-Enabled Androids from Oreo on up. You do lose some of the device specific things (hence, generic), but they're a great alternative if you're like us and stuck with next to no custom anything built for your device. There's a whole forum for them on here, I highly suggest checking it out- it's a pretty awesome option to have.
 

AsItLies

Senior Member
Nov 4, 2009
1,358
528
tucson
Google Pixel 3
In this case there is no tot file, no recovery, laf, or the like. GSI's are generic system images that are capable of being flashed to most Treble-Enabled Androids from Oreo on up. You do lose some of the device specific things (hence, generic), but they're a great alternative if you're like us and stuck with next to no custom anything built for your device. There's a whole forum for them on here, I highly suggest checking it out- it's a pretty awesome option to have.

Great, thnx, sorry for being a jerk but, this does work on a G8? Tested and proven? I ask because it's my understanding that without a match between the hardware encoded variant of the device and what's in the totc file, it won't boot.

you say there is no totc? then how does the hardware encoding get verified? See, that's why there are no custom roms. LG did this to keep people from crossflashing and it killed rom development.

Hey, if I'm wrong, feel free to point that out. But as far as I've discovered so far, a GSI doesn't get a free pass to bypass this mess LG has created with this mis-match hw / totc file.

cheers
 

SirOlive

Member
Apr 13, 2021
5
1
LG G8
Moto G Stylus 5G
Great, thnx, sorry for being a jerk but, this does work on a G8? Tested and proven? I ask because it's my understanding that without a match between the hardware encoded variant of the device and what's in the totc file, it won't boot.

you say there is no totc? then how does the hardware encoding get verified? See, that's why there are no custom roms. LG did this to keep people from crossflashing and it killed rom development.

Hey, if I'm wrong, feel free to point that out. But as far as I've discovered so far, a GSI doesn't get a free pass to bypass this mess LG has created with this mis-match hw / totc file.

cheers
Sorry for being short, but a simple Google search would back up everything I've written. I wouldn't have written this up if it didn't work, or if it was just a theory... I wouldn't have said that my Verizon G8 is running Havoc if it didn't work. I was able to flash with zero problems. With the Treble Project, Google has mandated that Android devices boxed with 11+ (possibly 10?) be capable of not only recognizing, but running GSIs as to assist developers in testing apps and builds in varying versions of Android as quickly, easily, and simply as possible. This means that not only can one download and flash Android releases downloaded directly from Google, but devs can use the source code to create versions of their ROMs that will apply to a wide array of models that would never have seen development otherwise. Because these are "generic" images and are based upon system architecture type alone- not a particular make/model- there are sometimes things overlooked. For instance, in our case, the audio processing and LG's camera software are not present. These are decently made up for by the presence of flashable mods, though, and the phone remains fully functional, Google Play Certified (if desired), and as reliable as the ROM you choose to flash.

Basically, Google>LG. LG wants to use the Android platform, they must abide by Google's rules. They need not go into great detail, nor allow their devices to be changed to something fundamentally non-LG, nor divulge any potentially propitiatory subject matter (once again, "generic"), but they must allow the device to be open to a certain level of customization as designated by Google.

Is it ideal? Not if you're lucky enough to have ROMs tailored for your specific phone. But for those left behind- like the G8- it's a fantastic workaround that does, in fact, work. As I'm sure you're still skeptical, I will add screenshots tomorrow to prove the validity of this seemingly ludicrous claim. In the meantime, please do some research on the topic- or better yet, give it a shot- there's gotta be a guide around here somewhere.
 

hooutoo

Senior Member
Apr 17, 2009
400
44
Ft. Lauderdale
Of [email protected]*$king course it works. I’ve flashed it to my sprint v50 (v450pm). Had the same QuadDac problem though. Couldn’t get a sound out of it. I mean no sound of any kind. Also couldn’t get it to activate on Google Fi. Will be watching to see if someone solves the Sound problem. We could just skip on past A11.
 

Kevin Guz

Member
Oct 22, 2021
5
0
LG G8
Of [email protected]*$king course it works. I’ve flashed it to my sprint v50 (v450pm). Had the same QuadDac problem though. Couldn’t get a sound out of it. I mean no sound of any kind. Also couldn’t get it to activate on Google Fi. Will be watching to see if someone solves the Sound problem. We could just skip on past A11.
Where did you get V50 engineering abl files as well as stock?, I just want to make sure to get the correct files
 

hooutoo

Senior Member
Apr 17, 2009
400
44
Ft. Lauderdale

There's no such thing, afak, of a v50 Eng abl. Read the header on the thread! If you don't have one of those phone models, don't! All of this seems to be predicated on the g8x eng abl which is the DL on that thread. READ that thread closely. I did, BL unlock and then flash A12 GSI.
 

Kevin Guz

Member
Oct 22, 2021
5
0
LG G8

There's no such thing, afak, of a v50 Eng abl. Read the header on the thread! If you don't have one of those phone models, don't! All of this seems to be predicated on the g8x eng abl which is the DL on that thread. READ that thread closely. I did, BL unlock and then flash A12 GSI.
Ok,ok
 

Kevin Guz

Member
Oct 22, 2021
5
0
LG G8
Hello, I followed your instructions as written but when I reboot my phone I am stuck at a boot logo cycle, but my comment doesnt have to do with that, I want to ask if maybe you know what could've gone wrong.

I also own a g8 from verizon, I do have bootloader unlock, and tried to install Havoc OS, I wanted to mention this in case it is useful
 
Last edited:

hooutoo

Senior Member
Apr 17, 2009
400
44
Ft. Lauderdale
Dude, I have no knowledge of G8, per se. My main goal was to get away from Sprint software on my v450pm. These phones are a little touchy. I do know that if you have a proven RESTORE method then you can mess around.. If you're Qfil_ing your phone you MUST have a backup of EVERY damn partition. I trashed my ftm partition and it was bad. Use telegram group for very good info. I have yet to be able to logon to Google Fi, an mnvo of Tmob. I've crossflashed to Eu A11, no go. I'm about to try some other roms, but again a backup will be needed.

Remember, you gotta have a way out or you're gonna pay $14 bucks to a Russian.
 

Kevin Guz

Member
Oct 22, 2021
5
0
LG G8
Dude, I have no knowledge of G8, per se. My main goal was to get away from Sprint software on my v450pm. These phones are a little touchy. I do know that if you have a proven RESTORE method then you can mess around.. If you're Qfil_ing your phone you MUST have a backup of EVERY damn partition. I trashed my ftm partition and it was bad. Use telegram group for very good info. I have yet to be able to logon to Google Fi, an mnvo of Tmob. I've crossflashed to Eu A11, no go. I'm about to try some other roms, but again a backup will be needed.

Remember, you gotta have a way out or you're gonna pay $14 bucks to a Russian.
Yeah, I know, like I said in my previous comment my phone got stuck in a boot loop, I fix it just by loading system_a partition in qfil, so I am gonna give it another shot and see if it works, already backed up every partition just in case anything goes wrong
 

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    This might be completely unnecessary (mods feel free to remove if it is), but I see a LOT of misinformation regarding GSI ROMs and the G8. So. Here's a guide/FAQ for those wondering if/what is possible:

    ***I'M NOT RESPONSIBLE IF YOU BRICK YOUR PHONE, LOSE YOUR DATA, OR OTHERWISE DAMAGE YOUR DEVICE. IF YOU CHOOSE TO FOLLOW THIS GUIDE, THE FATE OF YOUR DEVICE IS IN YOUR HANDS, NOT MINE, NOT YOUR MOTHER'S, NOT ANYONE OTHER THAN YOUR OWN***

    Prerequisites (yes, these are all NECESSARY. If you don't know how to unlock your bootloader or use fastboot, there are other guides here. Go find one.)
    • Unlocked bootloader (and the V50 engineering abl files as well as stock, plenty of guides here with download links)
    • QFIL/QPST
    • Basic Fastboot, ADB knowledge
    • BACKUP. I mean ALL YOUR DATA kinda backup. This WILL wipe your phone, do NOT come crying to me if you lose the last picture of your favorite sock. Not my fault.
    • GSI for Treble device (ab)
    • GApps (optional, but recommended)

    Instructions to Flash via Fastboot
    • WIPE YOUR PHONE
      • Yeah, completely factory reset that sucker. Doesn't matter if it's through recovery, settings, or adb, just bite the bullet and restore factory settings. You can technicially flash without doing this first, but you'll still have to wipe it before any flashed ROM will run. Sorry.
    • Boot to EDL (NOT download, your screen should be black, dev manager should show QD Loader 9008 COMx)
    • Use QFIL to flash engineering abl file to both a and b slots - yes, all this work just for fastboot.
    • Reboot to fastboot!
      • I just unplug my phone, use power + vol- to shut phone off and then reconnect while holding vol-, but you do you.
      • In case you don't remember, your touch screen WILL NOT WORK during this time, even if you fully boot to system! Completely fine and normal, means you're on the right track!
      • Fastboot Devices should yield "LG850UM", also good!
    • Open cmd prompt from platform_tools, copy path to desired GSI while you're in there
    • Run these commands line-by-line:
      • fastboot format system
      • fastboot flash system *Path_To_GSI.img*
        • This is where I usually repeat the 2 commands and attempt reboot while I still have fastboot, whether or not it changes anything I have no idea, but it's never given me problems so why fix it if it ain't broke?
      • fastboot flash abl_a abl_STOCK.bin
      • fastboot flash abl_b abl_STOCK.bin
      • fastboot reboot
    • Ta-Da! Your shiny new ROM should be up and running. Use TWRP or any kernel manager (I like SmartPak) to flash TWRP, GApps, blah blah blah.

    FAQ/Troubleshooting
    • Touchscreen still not working? Go back to EDL and load the stock abl bin files through QFIL, then reboot as normal.
    • You will likely be asked to input a password upon successful reboot, just enter your PIN/password, whatever you used to unlock your phone pre-flash
    • The cool things like QuadDAC and LG-specific tweaks will probably not work. Weigh your options before flashing.
    • Magisk comes pre-installed with most GSI's, just follow the prompts and you'll be just fine.
    • Don't want GApps? Just sideload desired apk's via ADB, or use the browser to search for them.
    • Can't I just use TWRP and make this whole process a lot simpler? Yep. But some of us don't have working TWRP or prefer using fastboot commands. This is for those people, don't hate.
    • Which ROMs work?? Not sure, haven't tried them all. Currently running HavocOS found in Treble GSI forum on here.
    • Help! I broke my phone! No, you probably didn't. It's advisable that you know how to emergency restore via LGUP prior to starting this process though. Please be specific as to what part of this "broke" your phone and why exactly your phone is "broken" if you're going to ask for help- "bricked device" has never helped anyone.
    • Rebooting is your best friend in this process, especially during the first boot. If anything starts to hang up or act funny, just give the phone a minute to catch its breath and, worst case, turn it off and back on again

    As previously stated, this is probably pointless, but given all I see on the G8 forum is "no custom ROM" or "why bother trying to *insert idea here*", I figured it might help some folks out. I'm sure I left a few things out, feel free to correct or provide input as necessary.