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Bootloader, Recovery, and the joy of unlocking

  1. Bootloader, Recovery, and the joy of unlocking, Reboot to the bootloader, or reboot in Safe Mode: step 1, image 1 of 3 Bootloader, Recovery, and the joy of unlocking, Reboot to the bootloader, or reboot in Safe Mode: step 1, image 2 of 3 Bootloader, Recovery, and the joy of unlocking, Reboot to the bootloader, or reboot in Safe Mode: step 1, image 3 of 3
    • All steps in this guide will vary from one phone model to another. Read your device's documentation to determine the specific steps required.

    • To power down most phones, hold down the power button until a prompt appears. Tap on the pop-up message. Some devices may have a "Power off" command in the software settings.

    • If your phone is crashing or locking up after boot, try rebooting into safe mode. In the previous step, tap and hold on "Power off" until the prompt changes to "Reboot to safe mode." Tap OK.

    • Most third party apps will not run under safe mode. If the phone runs okay, then reboot normally and start uninstalling apps until you determine which one was the culprit.

    • Some apps' settings will be lost or reset after using safe mode. You may have to set them up again.

    • With the phone in an off state, hold down buttons in a combination to enter the bootloader. Google Nexus models have specific combinations like holding Volume Down and Power simultaneously.

    • Your device's bootloader may look different from this Nexus 5 screen. That's okay. Note the essential information available to you here: phone model, product variant, serial/IMEI number, SIM and bootloader locked state.

  2. Bootloader, Recovery, and the joy of unlocking, Bootloader, fastboot: step 2, image 1 of 1
    • The bootloader often displays information like the phone model, version of fastboot, whether or not it is boot-unlocked or not.

    • For Google Nexus devices, you can now connect your phone to a computer (Windows, MacOS, Linux) running the Android SDK tools, allowing some commands to be sent.

    • The Android SDK fastboot command supports unlocking the bootloader, flashing factory images to Nexus phones, flashing a new recovery partition. Check the Android SDK documentation for further details, or type fastboot -h at the command line.

    • Flashing a phone can often wipe out all user data and settings. Fastboot flashing unlock (formerly fastboot oem unlock) on Nexus phones will erase all user data as a security precaution. Offload any information or media that you want to keep before unlocking a phone's bootloader.

    • Some manufacturers may supply custom code based on your phone's IMEI (unique serial number) which is required to unlock.

    • Flashing an Android phone with compatible ROMs (operating firmware and software) is part of the fun of tinkering with Android Phones. With the phone in the bootloader state, this is where you can change your phone's software suite. For example, Google provides complete "factory images" to return the Nexus models to a new, "out of the box" state.

  3. Bootloader, Recovery, and the joy of unlocking, Recovery is your friend: step 3, image 1 of 1
    • From your bootloader screen, toggling the volume buttons will offer functions like Start, Power Down, Restart Bootloader, and usually … Recovery. Pressing the Power button generally executes the displayed function.

    • The recovery partition is a rudimentary mini operating mode which allows loading updates, wiping the cache partition, and performing a factory reset to a phone that cannot boot properly (e.g. in an endless bootloop, never reaching an unlock screen). It's not called recovery for no reason -- it's an essential tool for restoring a broken phone.

    • Some phones are supported by third party recovery images, like ClockworkMod, with advance features including selective backup and restore, mounting partitions usually only accessible after the Android OS is running, and installing a root service.

    • Similar to Unix' superuser command, root allows the user to perform system-level actions. Rooting is a powerful tool that enables some features and access to the operating system while it is running.

    • Rooting suppresses built-in security protections of the operating system, and should only be done if you have full understanding of the risks. You should never grant an installed application root access, or permission to install a root service, without knowing exactly what it needs it for. 99.9% of apps will never need root access.

David Spalding

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