Android Fastboot Operations
⚠️ DANGER ZONE - Fastboot operations write directly to device partitions. Wrong images or interrupted operations can brick devices. Always verify:
- Correct device (check
fastboot getvar product) - Correct images for exact device model
- Bootloader is unlocked (for flashing)
- Battery > 50%
Entering Fastboot Mode
bash# From ADB (device running) adb reboot bootloader # Hardware buttons (most devices) # Power + Volume Down (hold until fastboot screen)
Basic Commands
bashfastboot devices # List connected devices fastboot getvar all # All device variables fastboot reboot # Reboot to system fastboot reboot bootloader # Stay in bootloader fastboot reboot recovery # Boot to recovery fastboot reboot fastboot # Boot to fastbootd (Android 10+)
Check Before Flashing
bash# ALWAYS run these first fastboot devices # Verify connection fastboot getvar product # Verify device model fastboot getvar unlocked # Must be "yes" for flashing fastboot getvar current-slot # Know current A/B slot fastboot getvar battery-level # Should be > 50
Bootloader Unlocking
Google Pixel
bash# 1. Enable OEM unlocking in Developer Options # 2. Boot to fastboot adb reboot bootloader # 3. Unlock fastboot flashing unlock # 4. Confirm on device with volume keys + power # WARNING: This wipes all data!
Other Manufacturers
| Brand | Process |
|---|---|
| OnePlus | fastboot oem unlock |
| Xiaomi | Mi Unlock Tool (waiting period) |
| Samsung | Uses Odin, not fastboot |
| Motorola | Request code from website, fastboot oem unlock <code> |
| Sony | Request code from website |
Check Unlock Status
bashfastboot getvar unlocked # yes/no fastboot getvar device-state # locked/unlocked fastboot getvar unlock_ability # Can be unlocked?
Flashing Partitions
Individual Partitions
bashfastboot flash boot boot.img fastboot flash recovery recovery.img # Non-A/B only fastboot flash dtbo dtbo.img fastboot flash vbmeta vbmeta.img # Disable verification (for custom ROMs) fastboot flash --disable-verity --disable-verification vbmeta vbmeta.img
Bootloader & Radio (Extra Careful!)
bash# These can hard-brick if wrong! fastboot flash bootloader bootloader.img fastboot reboot bootloader # REQUIRED after bootloader flash fastboot flash radio radio.img fastboot reboot bootloader # Recommended after radio flash
Temporary Boot (No Flash)
bash# Test before committing - reboots to normal after restart fastboot boot recovery.img fastboot boot patched_boot.img
A/B Slot Devices
Modern devices have two copies of each partition (A and B).
bash# Check current slot fastboot getvar current-slot # Returns: a or b # Set active slot fastboot set_active a fastboot set_active b # Flash to specific slot fastboot flash boot_a boot.img fastboot flash boot_b boot.img # Flash to both slots fastboot --slot=all flash boot boot.img
Dynamic Partitions (Android 10+)
Large partitions (system, vendor, product) live inside a "super" partition.
Fastbootd Mode
bash# Enter userspace fastboot fastboot reboot fastboot # Check if in fastbootd fastboot getvar is-userspace # Should return: yes
Flash Dynamic Partitions
bash# Must be in fastbootd mode! fastboot reboot fastboot fastboot flash system system.img fastboot flash vendor vendor.img fastboot flash product product.img
Virtual A/B Snapshots
bash# Check snapshot status fastboot getvar snapshot-update-status # Cancel stuck update (CAREFUL!) fastboot snapshot-update cancel
Recovery Operations
Enter Recovery
bashadb reboot recovery # Or: Power + Volume Up (varies by device)
ADB Sideload
bash# 1. In recovery, select "Apply update from ADB" # 2. Run: adb sideload update.zip
Flash Custom Recovery (TWRP)
bash# Test first (temporary boot) fastboot boot twrp.img # If it works, flash permanently # Non-A/B devices: fastboot flash recovery twrp.img # A/B devices (recovery in boot): fastboot flash boot twrp.img
Magisk (Root)
Installation
bash# 1. Extract boot.img from your firmware # 2. Transfer to device, patch with Magisk app # 3. Pull patched image adb pull /sdcard/Download/magisk_patched_*.img # 4. Flash patched boot fastboot flash boot magisk_patched_*.img # 5. Reboot fastboot reboot
Useful Magisk Commands (after rooted)
bashadb shell su -c "magisk --version" adb shell su -c "resetprop ro.debuggable 1"
Factory Reset / Wipe
bashfastboot erase userdata # Wipe user data fastboot erase cache # Wipe cache (if exists) fastboot -w # Format data + cache # Full flash with wipe fastboot -w flashall fastboot -w update image.zip
Danger Levels
| Level | Operations |
|---|---|
| ✅ SAFE | devices, getvar, reboot, boot (temp) |
| ⚠️ MEDIUM | flash boot/recovery/dtbo, set_active |
| 🔴 HIGH | flash system/vendor, erase, -w |
| ☠️ CRITICAL | flash bootloader, flash radio, flashing lock with custom OS |
Brick Prevention
Never:
- Flash images from different device models
- Interrupt a flash operation
- Lock bootloader with custom ROM installed
- Flash bootloader/radio without matching versions
Always:
- Verify device with
fastboot getvar product - Keep stock images available for recovery
- Use
fastboot bootto test beforefastboot flash - Maintain battery > 50%
Recovery from Soft Brick
bash# 1. Enter fastboot (Power + Vol Down) fastboot devices # 2. Flash stock boot fastboot flash boot boot.img # 3. For dynamic partitions fastboot reboot fastboot fastboot flash system system.img fastboot flash vendor vendor.img # 4. Wipe if needed fastboot -w # 5. Reboot fastboot reboot
For hard bricks (no fastboot access), you need EDL mode (Qualcomm) or manufacturer service tools.
Quick Reference
| Task | Command |
|---|---|
| Check connection | fastboot devices |
| Device info | fastboot getvar all |
| Unlock bootloader | fastboot flashing unlock |
| Flash boot | fastboot flash boot boot.img |
| Test recovery | fastboot boot twrp.img |
| Current slot | fastboot getvar current-slot |
| Switch slot | fastboot set_active a |
| Wipe data | fastboot -w |
| Reboot | fastboot reboot |
