// Use for fastboot operations, flashing partitions, bootloader unlocking, recovery mode, or partition management. Triggers on "fastboot", "flash boot.img", "unlock bootloader", "recovery mode", "TWRP", "Magisk", "partition", "sideload", "A/B slots". WARNING - These operations can brick devices if done incorrectly.
Use when building Android apps (Gradle CLI) or ROMs (AOSP, LineageOS). Triggers on "gradle build", "assemble", "AOSP", "LineageOS", "lunch", "mka", "breakfast", "brunch", "compile android", "device tree", "kernel build".
Use when working with Android devices via ADB - connecting devices, running shell commands, installing apps, debugging, taking screenshots, UI automation, viewing logs, analyzing crashes, or exploring system internals. Triggers on "adb", "logcat", "install apk", "debug android", "android device", "shell command", "screenshot", "dumpsys", "crash", "ANR".
Use when working with LineageOS custom ROM development, including syncing sources, building, device trees, repopick, Gerrit contributions, or LineageOS-specific features. Triggers on "LineageOS", "lineage-sdk", "breakfast", "brunch", "repopick", "vendor/lineage", "lineage.dependencies", "mka bacon".
| name | android-fastboot |
| description | Use for fastboot operations, flashing partitions, bootloader unlocking, recovery mode, or partition management. Triggers on "fastboot", "flash boot.img", "unlock bootloader", "recovery mode", "TWRP", "Magisk", "partition", "sideload", "A/B slots". WARNING - These operations can brick devices if done incorrectly. |
⚠️ DANGER ZONE - Fastboot operations write directly to device partitions. Wrong images or interrupted operations can brick devices. Always verify:
fastboot getvar product)# From ADB (device running)
adb reboot bootloader
# Hardware buttons (most devices)
# Power + Volume Down (hold until fastboot screen)
fastboot 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+)
# 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
# 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!
| 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 |
fastboot getvar unlocked # yes/no
fastboot getvar device-state # locked/unlocked
fastboot getvar unlock_ability # Can be unlocked?
fastboot 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
# 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
# Test before committing - reboots to normal after restart
fastboot boot recovery.img
fastboot boot patched_boot.img
Modern devices have two copies of each partition (A and B).
# 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
Large partitions (system, vendor, product) live inside a "super" partition.
# Enter userspace fastboot
fastboot reboot fastboot
# Check if in fastbootd
fastboot getvar is-userspace # Should return: yes
# Must be in fastbootd mode!
fastboot reboot fastboot
fastboot flash system system.img
fastboot flash vendor vendor.img
fastboot flash product product.img
# Check snapshot status
fastboot getvar snapshot-update-status
# Cancel stuck update (CAREFUL!)
fastboot snapshot-update cancel
adb reboot recovery
# Or: Power + Volume Up (varies by device)
# 1. In recovery, select "Apply update from ADB"
# 2. Run:
adb sideload update.zip
# 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
# 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
adb shell su -c "magisk --version"
adb shell su -c "resetprop ro.debuggable 1"
fastboot 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
| 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 |
Never:
Always:
fastboot getvar productfastboot boot to test before fastboot flash# 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.
| 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 |