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Guides

Step-by-step Android modding guides

Showing guides for a21s — show all guides

🔓 Bootloader Unlock

Unlock Bootloader

Wipes everything. Samsung Knox trips permanently on unlock — no way back.

8 steps ▼
  1. Back up all data — unlocking factory resets your device
  2. Enable Developer Options: Settings → About Phone → tap Build Number 7 times
  3. Enable OEM Unlocking in Developer Options
  4. Enable USB Debugging in Developer Options
  5. Connect to PC: adb reboot bootloader
  6. Unlock: fastboot flashing unlock (older: fastboot oem unlock)
  7. Confirm on device screen — wipe happens immediately
  8. Device reboots to stock setup wizard
🛠 Install Recovery

Install TWRP Recovery

Use the exact TWRP build for your device model number. Wrong builds can brick.

5 steps ▼
  1. Download TWRP .img for your exact device variant from twrp.me
  2. Boot to fastboot: adb reboot bootloader
  3. Flash: fastboot flash recovery twrp.img
  4. Boot into recovery immediately: fastboot boot twrp.img
  5. In TWRP swipe to allow modifications
🛠 Install Recovery

Install OrangeFox Recovery

OrangeFox is only available for select devices.

4 steps ▼
  1. Download OrangeFox .img for your device from orangefox.tech
  2. Boot to fastboot: adb reboot bootloader
  3. Flash: fastboot flash recovery orangefox.img
  4. Boot into recovery: fastboot boot orangefox.img
📦 Install ROM

Install LineageOS onSamsung Galaxy A21s

20 steps ▼
  1. Read through the instructions at least once before actually following them, so as to avoid any problems due to any missed steps!
  2. Make sure your computer has adb . Setup instructions can be found here .
  3. Enable USB debugging on your device.
  4. Make sure that your model number is one of the following (exact match required!): SM-A217F SM-A217M SM-A217F/DS SM-A217F/DSN SM-A217M/DS
  5. Boot your device with the stock OS at least once and check every functionality.
  6. Remove all Google accounts from your device to avoid “Factory reset protection”
  7. LineageOS is provided as-is with no warranty. While we attempt to verify everything works you are installing this at your own risk!
  8. Connect the device to a Wi-Fi network.
  9. Enable Developer Options by pressing the “Build Number” option at least 7 times, in the “Settings” app within the “About” menu
  10. Within the “Settings” app go to “Date and Time” and change the date to be 2 years in the past
  11. Reboot the device
  12. Go to the Developer Options menu in the “Settings” app and enable OEM unlock
  13. Power off the device, and boot it into download mode: With the device powered off, hold Volume Up + Volume Down and connect USB cable to PC. Now, click the button that the onscreen instructions correlate to “Continue” and/or “Unlock Bootloader”.
  14. Your device will reboot and format all user data, you may now unplug the USB cable from your device.
  15. Run through Android Setup, it is crucial that you connect to a Wi-Fi network when setting up the device
  16. Re-enable Development settings by clicking the “Build Number” option 7 times, in the “Settings” app within the “About” menu, and verify that “OEM Unlock” is still enabled in the “Developer options” menu.
  17. Enable Developer Options by pressing the “Build Number” option in the “Settings” app within the “About” menu From within the Developer options menu, enable OEM unlock.
  18. Download and install the appropriate version of the Heimdall suite for your machine’s OS Windows : Extract the Heimdall suite zip and take note of the new directory containing heimdall.exe . You can verify Heimdall is functioning by opening a Command Prompt or PowerShell in that directory and runnin
  19. Power off the device, and boot it into download mode: With the device powered off, hold Volume Up + Volume Down and connect USB cable to PC. Now, click the button that the on screen instructions correlate to “Continue”, and insert the USB cable into the device.
  20. For Windows users only : install UsbDk .
⚡ Root

Root with Magisk

Keep a backup of the original boot.img. Magisk is systemless — safer for updates.

7 steps ▼
  1. Unlock bootloader first
  2. Download stock boot.img for your exact firmware build
  3. Install Magisk app on device
  4. In Magisk: Install → Select and Patch a File → pick boot.img
  5. Copy patched_boot.img to PC
  6. Flash: fastboot flash boot patched_boot.img
  7. Reboot and open Magisk to verify root
⚡ Root

Root with KernelSU

Requires kernel-level support. Not all devices are supported.

5 steps ▼
  1. Check kernelsu.org for a supported kernel for your device
  2. Download the KernelSU kernel .img
  3. Flash: fastboot flash boot kernelsu_boot.img
  4. Install KernelSU Manager from GitHub releases
  5. Grant root from the Manager
⚡ Root

Root with APatch

Alternative to Magisk with kernel patch support.

5 steps ▼
  1. Download APatch from github.com/bmax121/APatch
  2. Extract boot.img from your stock firmware
  3. In APatch app: patch boot.img
  4. Flash patched boot: fastboot flash boot patched_boot.img
  5. Reboot and verify in APatch Manager
🔄 Restore / Unbrick

Restore Stock / Unbrick

Always use firmware matching your exact region and model number.

7 steps ▼
  1. Download official stock firmware for your exact model and region
  2. Samsung: use Odin — flash AP/BL/CP/CSC files
  3. Xiaomi/Poco: use MiFlash in EDL/fastboot mode
  4. Google Pixel: use Android Flash Tool at flash.android.com
  5. OnePlus: use MSM Download Tool for hard bricks
  6. Other devices: check XDA for your specific model
  7. After flash: device reboots to stock
💰 Buy & Sell

Buying & Selling Modified Devices

Unlocked bootloader = lower resale value. FRP locks are illegal to bypass on a device you don't own.

7 steps ▼
  1. BEFORE SELLING: Factory reset and remove Google account (FRP)
  2. BEFORE SELLING: Restore stock ROM and re-lock bootloader if possible
  3. BEFORE SELLING: Disclose Knox trip status to Samsung buyers — it shows in settings
  4. BEFORE BUYING: Ask if bootloader is unlocked
  5. BEFORE BUYING: Check IMEI on imei.info — confirm not blacklisted
  6. BEFORE BUYING: Test camera, speakers, fingerprint, charging
  7. BEFORE BUYING: Verify model number matches your region