After long and tedious process of unlocking bootloader in my Xiaomi Redmi Note 4 phone using linux, to sum up I decided to write definitive tutorial about it. I have collected all information that were scattered around internet and gathered them in one place.

Note

This tutorial is written especially for MTK SOC devices, so if you have locked bootlader on other Xiaomi phone that Redmi Note 4 and it is MTK, then you can try unlocking it using tools and methods presented here.

Disclaimer

  1. I don’t take any responsibility for bricked or broken devices.
  2. You are performing all steps at your own risk.
  3. Your warranty in most cases will be void.

General information

Probably many of you knows that bootloader unlocking process in recent Xiaomi phones is difficult and requires a lot of work. First of all it requires special tool called Mi Unlock. Unfortunately it works only in Windows operating system. Second thing is that to unlock bootloader you must ask for premission first. Then you need to wait for SMS message that you are allowed to proceed to next steps. To sum up this part - we will need to use Windows operating system anyway. Right now there is no way to unlock bootloader using linux only :( So install one on physical machine or virtual one.

Before you start

To make sure that bootloader in your Xiaomi Redmi Note 4 MTK is actually locked we will use Android Fastboot tool.

  • Install Android tools in your system (search for android-tools in package manager)

  • Turn off your phone

  • Press and hold Volume (-) and Power buttons together. Relase buttons when Fastboot screen appears.

  • Connect your phone to linux PC

  • Issue following command to check if device is connected: 

    fastboot devices

    Non empty list of fastboot devices should appear

  • Issue next command to check if bootloader is locked: 

    fastboot getvar unlocked
    If you get status like: 
    unlocked: "no"
    that means you need to unlock, so continue reading tutorial.

    If this appears: 

    unlocked: "yes"
    then you don’t need to do anything.

Unlocking process

Preparation

  • Create Xiaomi Account if you don’t have one

    • Go to https://account.xiaomi.com/
    • At button of page change language from Chinese to English
    • Click on Create Mi Account
    • Fill form and click Create Mi Account

  • Pass all security check-ups

    • Login to your account https://account.xiaomi.com/
    • Fulfill all 4 tasks (Password, Recovery email,…)
    • Make sure there is green bar saying that your account is secure

    This step in necessary to make sure your bootloader unlock permission grant application will be accepted faster.

  • Go to https://miui.com/unlock/apply.php and apply for unlocking your device. Provide reason of unlocking like:

    I want to install custom ROM.

  • Wait for grant permissions SMS message. Myself, I have waited for 10 hours. This time my vary between users.

  • After receiving SMS go to https://drive.google.com/open?id=0B9wtW2KGOf0RYWhLNG9ybWM3OG8 and download old version of Mi Flash tool. This is needed for bypass possible error saying that binding time is too short.

  • Install application in windows machine or go to next section where I described process of preparing virtual machine.

Using Virtual Machine instead of physical Windows PC

  • Install Virtual Box via package manager
  • Create new Virtual Machine and install Windows on it (I recommend using Windows 7)
  • Install VirtualBox Guest Addons on your virtual machine. While it is running, click on Devices -> Install Guest Addons. Finish installation inside virtual machine.
  • Power off virtual machine
  • Install Oracle VM VirtualBox Extension Pack
    • If you have it in your linux distribution repository then install from it
    • If not then install manually
      • Download https://www.virtualbox.org/wiki/Downloads
      • Launch virtual box
      • Go to File -> Preferences -> Extensions
      • Click on small orange button and select downloaded file
      • Go through install wizard steps and finally provide root password for installation completion
      • Restart virtual box
  • Go to your virtual machine settings
  • Select USB
  • Check Enable USB Controller
  • Select USB 2.0 (EHCI) Controller
  • Click on small blue icon
  • New Filter 1 position will appear on list
  • Make sure new filter is checked
  • You can test if USB is working by plugging USB Stick to your PC while virtual machine is running. It should appear inside VM.
  • If everything is working install Mi Flash on virtual machine

Flashing China Developer ROM

To be able to unlock bootlader on Redmi Note 4 you need China Developer ROM installed on your device.

  • Backup all your important data

  • Make sure that your phone battery is at least 50% charged

  • Download Redmi Note 4 Latest China Developer Version Fastboot ROM from http://en.miui.com/a-234.html

  • Download custom cust.img (RAR MD5: 00d47e8fd3e64bf989dd329ebc37d6a3):

  • Extract ROM archive

  • Extract cust archive

  • Replace cust.img in images/ dir with custom one you have downloaded

  • Download latest version of SP Flash Tool for Linux

  • Extract downloaded archive

  • Add your user to special linux group

    • For ubuntu 
      sudo adduser username dialout
    • For arch 
      sudo gpasswd -a username uucp

  • Logout and login again to make change live

  • run sp_tool.sh which is located in folder where you extracted SP Tool archive

  • Set Download Agent to MTK_All_In_One_DA.BIN

  • Set Scatter-loading File to MT6797_Android_scatter.txt which is located in ROM images/ dir

  • Uncheck preloader position on the list of images to push to device

  • Turn off phone

  • Click Download Button in SP Flash Tool

  • Click and hold Volume Down (-) on phone and while holding it plug your phone to PC via USB cable

  • If phone is detected then yellow bar appears at button and flashing process begins. You can release Volume Down (-) button.

  • After flashing is done Download OK message appears.

  • You can unplug your phone and turn it on. First boot might take up to 10 minutes. This is normal.

Binding Mi Account to phone

Now you when you have China Developer ROM installed it is time for got throught setup wizard. After your phone is ready you must bind it to Xiaomi Account which you have created in previous steps. Follow this steps in configuration wizard:

  • Change language to English
  • Connect to network
  • Login to Mi Account (very important step)
  • Finish wizard

After wizard is done:

  • Go to Setting -> About phone -> Tap on MIUI version for 10 times until message saying that your are developer now appears
  • Go to Setting -> Additional settings -> Developer options
  • Turn on USB Debuging

Unlocking Bootloader

  • Start Mi Unlock Tool on Windows
  • On first screen provide username and password and login to your Xiaomi account
  • Turn off your phone and turn in on in Fastboot mode. To do so, hold Volume (-) and Power buttons together. Release buttons when Fastboot screen appears.
  • Follow steps in Mi Unlock app and connect your phone to PC via USB cable when you are asked to do so.
  • If everything works out well Mi Unlock will stop at 100% and your bootloader will be unlocked (you can verify this by using fastboot tool method described at beginning of tutorial).
  • Enjoy!

What to do next ?

Now when you have your bootloader unlocked you will probably want to flash custom Recovery to manage your ROMS. This process will be described in next post.

References