I'm attempting to root a Samsung Galaxy A20s (Android 10). I've already patched the boot image with Magisk and enabled "OEM Unlocking" in Developer Options. I ran

adb reboot fastboot

However, when it reboots, fastboot devices shows no devices. Looking online, I found the odin4 utility and attempted to flash the phone by

tar cf boot.tar boot.img
./odin4 -b boot.tar

However, it failed with

Check file : boot.tar
Setup Connection
Receive PIT info
success getpit
Upload binaries
Close Connection
Fail request receive -5
FAIL close
Fail Close Connection

On my phone's screen, I see

...KG STATUS: CHECKING # I can't read the beginning of the line because it's in the round corner of the screen.
AP SWREV: S1, T1, R1, A2, P2
AP SWREV: K 2, S 2
DID : <hex>
download mode !!
    Custom Binary(boot) Blocked by OEM LOCK

How do I unlock the OEM?

1 Answer 1


Following these instructions did it for me. In summary, after powering off the phone, you have to hold down both volume buttons and then plug the phone into your computer via USB.

Eventually, a screen will appear which will allow you to press the Volume Up button in order to unlock the bootloader.

From the reference:

1. Tap "Settings" Menu on Galaxy A20s, then you have to tap "About" option.
2. Tap "Software Information" option.
3. Tap "Build number" option several times until you see "You are now a developer" message.
4. Tap "Settings" Menu again.
5. Tap "Developer options", then activate "OEM unlocking" option.
6. Now you have to activate "USB debugging" option.
7. Switch off your phone.
8. Download and install Samsung USB driver on desktop.
9. Connect your phone with computer via USB cable while pressing Volume down button and Volume up button simultaneously. Your Samsung Galaxy A20s (SM-A207F, SM-A207M) will enter into download mode.
10. Long Press Volume up button for a few seconds to enter Device Unlock Mode.
11. Press Volume up button again to unlock bootloader.
  • the steps written lead to exactly situation of question: Custom Binary Blocked. you are missing important step (12. finish initial setup) 13. = repeat 1.-5. to actually disable VaultKeeper (and step 6. usb-debugging is not needed for Odin btw)
    – alecxs
    Jan 31, 2023 at 20:16

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