Fastboot

Fastboot is a command line tool used to directly flash the filesystem in Android devices from a host via USB. It allows flashing of unsigned partition images. It is disabled in production devices since USB support has been disabled in the bootloader. You must have an Engineering SPL, or an SPL that is S-OFF.

After installing the Android SDK or ADB Standalone you can use 'fastboot' in addition to the more common ADB.

Verify SPL S-OFF

With the exception of the Google Nexus One (which has an OEM unlock), when you boot the device into the bootloader, you should see S-OFF (security off) on the top line. If you see S-ON, or you see a four-color rainbow background, the SPL does not support fastboot. You will need to install a fastboot compatable SPL, such as HardSPL or any of the Engineering SPLs for various devices. See the device specific page for further instructions.

Access bootloader

1. Make sure you have ADB or the SDK installed.
2. Linux & OS X only: Download fastboot for the appropriate operating system for your computer.
3. Place the executable in the proper place, usually:
   • Linux: ~/android_sdk/tools/ or ~/bin/
   • OS X:
   • Windows: C:\Android_SDK\Tools or C:\Program Files\adb
4. Turn off the device.
5. Boot device into bootloader
6. Make sure the device is in FASTBOOT and not HBOOT
7. Connect the device to the computer via USB.
8. On your computer, open terminal and run:

   fastboot devices

You should see something similar to:

List of devices attached 
HTXXXXXXXXXX	device

fastboot --help

usage: fastboot [ <option> ] <command>

commands:
 update <filename>				reflash device from update.zip
 flashall					flash boot + recovery + system
 flash <partition> [ <filename> ]		write a file to a flash partion
 erase <partition>				erase a flash partition
 getvar <variable>				display a bootloader variable
 boot <kernel> [ <ramdisk> ]			download and boot kernel
 flash:raw boot <kernel> [ <ramdisk> ]		create bootimage and flash it
 devices					list all connected devices
 continue					continue with autoboot
 reboot						reboot device normally
 reboot-bootloader				reboot device into bootloader

options:
 -w						erase userdata and cache
 -s <serial number>				specify device serial number
 -p <product>					specify product name
 -c <cmdline>					override kernel commandline
 -i <vendor id>					specify a custom USB vendor id
 -b <base_addr>					specify a custom kernel base address
 -n <page size>					specify the nand page size. default:2048

Typical Partition Layout

For Reference when flashing partitions

Examples

Manual Nandroid restore

Make a Nandroid backup, and copy the folder off your SD card to your desktop.

cd ~/Desktop/path/to/backup/

fastboot flash userdata data.img

fastboot flash system system.img

fastboot flash boot boot.img

fastboot reboot

Flash Custom Recovery.img

fastboot flash recovery /path/to/<recovery>.img

fastboot reboot

Flash Custom boot.img

You should make a Nandroid backup first, in case you need to recover your boot.img

fastboot flash boot /path/to/<boot>.img

fastboot reboot

Development

If you are developing a kernel, you may find it helpful to delete your boot.img and recovery.img to force booting into fastboot:

fastboot erase boot

fastboot erase recovery

You can then manually boot from your custom kernel and a ramdisk:

fastboot boot <kernel> <ramdisk>

Once you have a working kernel and ramdisk, you can automagically combine them within fastboot:

fastboot flash:raw boot <kernel> <ramdisk>