android

Android bootloader/fastboot mode and recovery mode explained/Android boot process


Besides normal booting of an android device, there are two more systems maintenance mode. The bootloader or fastboot mode and the recovery mode. We can get into both the modes via startup key combinations or by using adb commands.

android, booting, recovery, fastboot, bootloader, adb boot-loader, adb recovery
Android booting process, recovery mode, boot-loader/fastboot mode

What is a bootloader and how to get into the bootloader mode on your android device?

A bootloader is a computer program that loads an operating system (OS) or runtime environment for the computer after completion of the self-tests.

Bootloader is like BOIS to your computer. It is the first thing that runs when you boot up your Android device. It packages the instructions to boot operating system kernel. Basically, Android device has a storage space(disk) that has several partitions, which holds the Android system file in one and all the app data in another. Bootloader serves as a security checkpoint that is responsible for checking and initializing the hardware and starting software. You can get into this mode using adb command as well as by pressing device-specific buttons.

To enter into fastboot mode using adb command use the following steps:

  1. Ensure you have adb and fastboot tools installed on your system
  2. Appropriate usb drivers installed on the PC for your android device
  3. USB debugging is activated on your phone
  4. Connect your android device with your computer over a usb 2 port

Test the connectivity using the following command (provided your phone screen is unlocked)

adb devices

should give output such as
List of devices attached
…………………… device

to get into fastboot mode use the following command

adb reboot-bootloader

Once you enter your device screen shall indicate that has entered in fastboot mode

the following command will list the connected device which is in fastboot mode

fastboot devices

shall display something like

mt6582_phone fastboot

On the device screen you should see something like the following

fastboot,bootloader,android, adb reboot-bootloader fastboot-bootloader-1
Some of the most commonly used “fastboot” commands include:

  • flash – rewrites a partition with a binary image stored on the host computer
  • erase – erases a specific partition
  • reboot – reboots the device into either the main operating system, the system recovery partition or back into its boot loader
  • devices – displays a list of all devices (with the serial number) connected to the host computer
  • format – formats a specific partition; the file system of the partition must be recognized by the device

to get out of the bootloader/fastboot mode

use

fastboot continue

or

fastboot reboot

Fastboot/recovery more (Summery)
Fastboot mode/recovery mode is mostly used to erase or install various images such as system, boot, userdata, and more. You may end up using fastboot tool and fastboot/recovery mode when you are installing a custom rom or restoring factory image on your android device.

What is android recovery mode, custom recovery and how to get into the recovery mode?

Android devices come with Google’s recovery environment, this is also known “stock recovery.” You can boot to the recovery system by pressing device-specific buttons as your android device or use adb command that boots your device to recovery mode.

These options can be selected using the volume up/down button and power button. In this mode, adb or fastboot tools has no use.

There are various custom recovery /third party recovery environments are available such as Cyanogen recovery, ClockworkMod recovery (CWM), Team Win Recovery Project (TWRP) etc. You can install custom recovery from the bootloader/fastboot mode. Custom recovery images are usually has additional features such as better backup and recovery. In general, custom recoveries are only necessary if you plan on flashing a custom ROM. Most Android users wouldn’t even notice a difference between a device with the stock recovery system installed and one with a custom recovery.

To enter into recovery mode using adb command use the following steps:

  1. Ensure you have adb and fastboot tools installed on your system
  2. Appropriate usb drivers installed on the PC for your android device
  3. USB debugging is activated on your phone
  4. Connect your android device with your computer over a usb 2 port

Test the connectivity using the following command (provided your phone screen is unlocked)

adb devices

should give output such as
List of devices attached
…………………… device

to get into recovery mode use the following command

adb reboot recovery

android recovery mode, adb reboot recovery

Once in recovery mode, shall see a recovery menu, which provides list of fixed options. such as

  • reboot system
  • apply update from SD card
  • apply update from cache
  • wipe data/factory reset
  • backup user data
  • restore user data

To exit the recovery mode, select reboot system now and the system will boot back into the installed system.

Advertisements

11 thoughts on “Android bootloader/fastboot mode and recovery mode explained/Android boot process

  1. The tablet is blacklisted so i tried to robot it so its just click to fastboot and it does not want to go back how will i fix to get back to recovery mode

  2. Hi…well my device is not listed in the adb devices. It just shows…list of devices and then it’s blank..I have enabled USB debugging and I use lenovo k3 note

    1. Hi Harish,
      I too have lenovo k3 but I can see easily the device under adb devices.
      1. you have to use latest adb (mine is 1.0.32). you can check your version using #adb version command.
      2. Authenticate your device when you connect your device after enabling usb debugging

      hope it helps.

  3. When I type the command “adb devices” more than one show up, and when I try more commands it says “error: moer than one device/emulator”. What should I do? I’m trying to boot my S2 into recovery mode because it crashed while installing a custom ROM.

    1. This happens if you have an emulator like BlueStacks installed on your PC.Exit blue stacks by right clicking its tray icon or go into task manager and end the process of BlueStacks and see if it works.

  4. When I Type “adb reboot recovery” my device Reboot normally not entering in recovery mode..My Device Is Sony Xperia Z.

  5. Muchas gracias!! desde México

    Thanks so much!!
    this is very helpful when you have an Android phone with power on/off button damaged

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s