How To Guide [Magisk][US/CAN BL Unlock] Root for the Galaxy S21 Series (B/N/0/U/U1/W)

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Apr 23, 2021
Thanks for all the info provided from this thread.
Bit of a noob to this and trying to get 'adb root' access for a GS21 Ultra (SM-G998N).

I completed the steps to unlock bootloader and flashed patched boot.img which passed on Odin.
Had to factory reset and re-install Magisk app which brought up dialog to complete steps and reboot.

I think all steps make sense at this point, and device shows up after 'adb devices' after enabling USB debugging.
My question is why I can't get root access with 'adb root'? Still get 'adbd cannot run as root in production builds' message.


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    yeah, and people like you are just out to make some money......
    You either want to use the service or you don't, its that simple.

    He has told you why theres a charge.. the unlock tokens are device specific and have to be purchased so there is no way to provide it for free.

    If the service wasnt an option you would come to usa/can device threads and see NO development whatsoever so that being said there is 100x more development now because of the service.

    I understand some wish everything was free but you cant expect us to spend money out of our own pockets to unlock everyone do you?

    Just saying it is what it is.. source charges per unlock so we have to charge per unlock. There isnt anyone I know that can make tokens else it would be well known and posted for free but it simply isnt that way. No need for making accusations about others trying to "make money" because I assure you its not very lucrative.

    Also, we have contributed "for free" for years (myself over a decade) and continue to contribute for "free" so to say he is in it for money is just not true.

    If you dont agree with the service or dont want to pay for it then thats your decision, no need to go at the dev for something out of their control for providing an option that wouldnt otherwise exist.

    Thats my opinion anyway lol
    Thank You very much for your awesome work!
    I have a HK device with a "G980ZHU1****" build number and before attempting to root, I noticed that it wants to do an OTA update to a "g9980ZHU2****" -- does this mean that if I let this OTA happen, I won't be able to unlock and root?

    I was thinking of first installing this OTA, and then rooting afterwards, so I have the latest version after the root. But is it a bad idea then? Or is the HK version 2 also rootable?

    PS: How and when can I do the update then? Never? As far as I understand it, if you update you loose root, but if updating to a version 2 will lock the bootloader, then am I stuck with my current version of the OS?
    HK devices are ok you can update to any firmware, we were talking about US devices.
  • 22
    Note: this guide copied from topjohnwu's. Original guide here

    US/Canada bootloader unlock thread:

    Before Installing Magisk
    • Installing Magisk WILL trip KNOX
    • Unlocking bootloader for the first time will do a data wipe.

    If you already have Magisk installed, it is strongly recommended to upgrade directly via Magisk Manager using the “Direct Install” method. The following tutorial is only for initial installation.

    Getting Started

    Before you start:
    • This tutorial assumes you understand how to use adb and fastboot
    • Your device’s bootloader has to be unlocked
    • Make sure to remove any “boot image mods” such as other root solutions before installing Magisk. The easiest way is to restore the boot image with factory images, or reflash a non-prerooted custom ROM
    • If you plan to also install custom kernels, install it after Magisk
    Download and install the latest Canary Magisk Manager (may have problems but the only one working for now.. We use the app to gather some information about your device. In the home screen, you should see this:


    Pay special attention to the Ramdisk info. If the result is Yes, congratulations, your device is perfect for installing Magisk! However, if the result is No this means your device’s boot partition does NOT include ramdisk. This means you will have to go through some extra steps to make Magisk work properly.

    Unlocking Bootloader

    Unlocking BL on modern Samsung devices have some caveats, so I figure this would be helpful.
    • Allow bootloader unlocking in Developer options → OEM unlocking
    • Reboot to download mode: power off your device and press the download mode key combo for your device (Vol Down + Vol Up) while connected to usb.
    • Long press volume up to unlock the bootloader. This will wipe your data and automatically reboot.

    If you think the bootloader is fully unlocked, it is actually not! Samsung introduced VaultKeeper, meaning the bootloader will still reject any unofficial partitions before VaultKeeper explicitly allows it.
    • Go through the initial setup. Skip through all the steps since data will be wiped again later when we are installing Magisk. Connect the device to Internet during the setup.
    • Enable developer options, and confirm that the OEM unlocking option exists and is grayed out. This means the VaultKeeper service has unleashed the bootloader.
    • Your bootloader now accepts unofficial images in download mode.

    Patching Boot Image

    If your device has boot ramdisk, you need a copy of the boot.img

    • Use either Frija or Samloader to download the latest firmware zip of your device directly from Samsung servers.
    • Unzip the boot.img from AP and copy the file to your device.
    • Press the Install button in the Magisk card
    • Choose “Select and Patch a File” in method, and select the stock boot image
    • Magisk Manager will patch the image to [Internal Storage]/Download/magisk_patched.img.
    • Copy the patched image to your PC
    • Flash the patched boot image to your device.
      For most devices, reboot into fastboot mode and flash with command:
      fastboot flash boot /path/to/magisk_patched.img or
      Rename magisk_patched.img to boot.img and use 7zip to make flashable tar of your boot.img
      Reboot to download mode. Open Odin on your PC, and flash boot_patched.tar as AP.
    • Reboot and voila!

    Patching AP

    • Use either Frija or Samloader to download the latest firmware zip of your device directly from Samsung servers.
    • Unzip the firmware and copy the AP tar file to your device. It is normally named as AP_[device_model_sw_ver].tar.md5
    • Press the Install button in the Magisk card
    • Choose “Select and Patch a File” in method, and select the AP tar file
    • Magisk Manager will patch the whole firmware file to [Internal Storage]/Download/magisk_patched.tar
    • Copy the patched tar file to your PC with ADB:
      adb pull /sdcard/Download/magisk_patched.tar
      Do NOT use MTP as it is reported to corrupt files.
    • Reboot to download mode. Open Odin on your PC, and flash magisk_patched.tar as AP, together with BL, CP, and CSC (NOT HOME_CSC because we want to wipe data) from the original firmware. This may take some time (>10 mins).
    • After Odin is done, your device should reboot. You may continue with standard initial setup.
      If you are stuck in a bootloop, agree to do a factory reset if promted.
    • Although Magisk is installed, it still need some additional setup. Please connect to the Internet.
    • Install the latest Magisk Manager and open the app. It should show a dialog asking for additional setups. Let it do its job and the app will automatically reboot your device.
    • Voila! Enjoy Magisk 😃
    @topjohnwu for magisk and guide, If you appreciate his effort, show some love and support :)

    The latest Magisk Canary release (21409) contains the fix needed for the S21 devices, yes (but being a Canary release there are of course other bugs).

    But, @afaneh92, since you're just copying @topjohnwu's installation instructions exactly, word for word, wouldn't it just have been easier to link to those instructions and let people know that Magisk Canary releases now can root the S21 Ultra (and maybe also warn people that the Canaries can be buggy)?
    Thanks, but that doesn't apply to the S21 :coffee:
    Use latest magisk canary, I have rooted my S21 Ultra.
    US/Canada devices has no oem unlock toggle!
    Unlock service here

    How to get OEM Unlock option back for Non US/Canada device?
    1. Open the Settings app. Tap on General Management → Date and time.
    2. Use the toggle button to disable Automatic date and time.
    3. Set date option will be enabled now. Tap on it, and set the date to about 10-20 days earlier.
    4. Enable developer options.
    4.a Go to your device Settings.
    4.b Select ‘About phone’ » tap seven times on ‘Build number’.
    └ This will enable Developer options under Settings.
    4.c Go back to Settings » scroll down to the bottom and you’ll see Developer options menu.
    5. Open developer options (in the Settings app itself), and find the option called ‘Auto update system‘. Use the toggle button to disable it.
    6. Now, go back to the main screen of Setting, and then tap on Software update.
    7. Disable the option ‘Download updates automatically‘.
    8. Tap on ‘Download updates manually‘ option, but it will give you an error because of the wrong date, so it’s fine.
    9. Restart the device.
    10. Go to Settings > Developer options. The OEM unlock option should be enabled now.
    I assume this will trip Knox right?
    Read the very first bullet, lol
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