Question Bootloader is unlocked but can't access fastboot mode

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GIutton

Senior Member
Dec 26, 2021
73
11
OnePlus 8T
Samsung Galaxy S21 FE
Been trying to find out if there is a way to reflash the bootloader/fastboot to the phone?

Or how about relocking the bootloader without fastboot mode? osm0sis posted some tools that could do it on some older phones but haven't seen anything like it for newer ones so maybe it's not possible anymore. I have the phone rooted but if I can get back to stock with a locked bootloader I'd at least be happy.
 

Quake94

Senior Member
Jan 24, 2009
83
18
You could run the getvar command and compare partitions
Maybe try flashing "vendor_boot" or "abl" from the fastbootd.
Fastboot is stored on "abl" partition, so a bit of precaution
I would recommend backing them up before flashing over
 

GIutton

Senior Member
Dec 26, 2021
73
11
OnePlus 8T
Samsung Galaxy S21 FE
You could run the getvar command and compare partitions
Maybe try flashing "vendor_boot" or "abl" from the fastbootd.
Fastboot is stored on "abl" partition, so a bit of precaution
I would recommend backing them up before flashing over
When I use the MSM tool it flashes the "vendor_boot"

Do you know where I can get a copy of the abl partition? I am guessing it is not the abl.elf file found in the firmware ofp? And do I use dd to backup the file located in dev/block/by-name/abl_<a,b>?

I will try it but idk if it's going to allow me to flash the abl partition in fastbootd though. Ever since I tried doing a local install of A.20 then I MSM tool it back to A.17 and took the A.20 update ota (was trying various things to see if it would fix it) now it wont even flash the boot.img anymore. I get FAILED (remote: No such file or directory). Have already tried the MSM tool again to go back to A.17 but still can't flash a boot.img. So now I'm back to having an unlocked bootloader that I cannot relock and also cannot root the phone either lol.

Edit: "fastboot oem device-info" fails and "fastboot getvar all" gives me a completely different output from what you show. Not a single line is the same for me to be able to compare it to. And oh yeah I can't root the phone so I won't be able to backup the abl partition huh?

Edit again: okay so no idea why this worked but I tried "fastboot flash boot_b boot.img" and this worked and allowed me to root the phone. Last time I rooted I definitely used "fastboot flash boot boot.img" so idk why that stopped working but at least I am now rooted again. Also wanted to add that even after I flash the phone with MSM tool, USB debugging is enabled so something/some partitions are not being overwritten. I know MSM tool doesn't seem to overwrite the persist.img so could something in there be causing this? Or any other partitions not being overwritten that could potentially cause this?
 
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  • 1
    Here are some ideas:
    - What happens when you run adb reboot bootloader?
    - Cache and userdata wipe?
    - Read through this, maybe helpful:
    - Do you have root access? If so, you could maybe try
    - Going to system - upgrade - local update, and feeding it A.18.
    Here is a stock 300mb a.17 - a.18 update file, I don't have the 5GB one unfortunately.
    -In addition to above, maybe you could extract it and replace boot.img with a patched one, and pack back up as update file. Although this may throw out a checksum error when attempting to install..
    1
    Here are some ideas:
    - What happens when you run adb reboot bootloader?
    - Cache and userdata wipe?
    - Read through this, maybe helpful:
    - Do you have root access? If so, you could maybe try
    - Going to system - upgrade - local update, and feeding it A.18.
    Here is a stock 300mb a.17 - a.18 update file, I don't have the 5GB one unfortunately.
    -In addition to above, maybe you could extract it and replace boot.img with a patched one, and pack back up as update file. Although this may throw out a checksum error when attempting to install..
    When I run adb reboot bootloader the phone tries but then the screen glitches for a second then reboots into the system. I get the same result when I hold power and volume down buttons. Have tried factory defaulting from the settings menu and also tried wiping data from the recovery.

    I do not have root access but the bootloader is unlocked. I tried using the exploit shared by Rapper_Skull to get temporary root access and it said it had worked but the magisk app does not recognize it as rooted and "adb shell su" is not recognized either. Rapper_Skull explained it was not within the scope of the exploit. Maybe it could be modified to do it somehow but that is beyond me.

    I would love to try a local update with a patched boot image but I can't seem to find the proper OTA for my nv_id 10100110 MEA and because of the nv_id the Android 13 beta and rollback packages wont work either. Not too hopeful on this though as you said it will likely give a checksum error. From what I have read the MSM or QFIL tools should be able to do it, but would need to repack the ofp file with a patched boot for the MSM tool and nodoby has gotten QFIL to work that I have seen.

    I will definitely read through the URLs you posted but turning on OEM unlocking from fastboot wont be an option for me since I can't get into it. In desperation I also scrolled through every single adb shell list settings <system/secure/global> output on this phone and my old OP 8T looking for a line item for OEM unlocking I could modify or add but alas there isn't one. Also tried talking to realme and they basically told me to go kick rocks because I am in the US so no support or warranty. They wouldn't even sell me a motherboard!

    I have tried the MSM tool a couple times but it never worked. I am like 80% sure the tool kept flashing to active _b slot so I think my inactive _a slot should still contain my patched A.17 boot.img. I am very tempted to try flashing with the MSM tool again but unplugging the cable when it goes to clear/write the boot partition to mess it up. My thinking being that it would force the phone back onto slot _a just like it would do if an update fails, but that just sounds like such a dumb idea that it couldn't possibly work lol. Even if I do it and mess something up I should still be able to flash it with MSM again to fix it right? EDIT: Never mind my active slot is _a. When I took the A.18 update it went into slot _b meaning A.17 with my patched boot was on slot _a so the MSM tool must have been writing to the inactive slot and I only paid attention on the second flash to slot _b.
    1
    Someone suggested I try adb shell reboot fastboot and that booted the phone into fastbootd mode but I get no output from "fastboot devices". As far as I can tell it looks just like recovery only the title says Fastbootd Mode instead of "RECOVERY".
    Update your fastboot drivers.
    1
    Well I updated my drivers and that got the phone recognized in fastbootd mode. I tried fastboot boot magisk-patched-boot.img but that failed, however, fastboot flash boot magisk-patched-boot.img did work so I was finally able to root the phone and apply the safetynet fix which ungreyed OEM unlocking and allowed me to flip it back on. Unfortunately that did not fix the bootloader/fastboot issue. No matter what I still cannot get into fastboot mode.

    I was thinking of trying fastboot flashing lock to see if I can relock the bootloader from fastbootd mode but I would rather not make things worse by doing something I shouldn't be doing in fastbootd mode.