[Upgrading, Modifying and Unlocking] bogdann8:
Hi all,

If you've bought a Lenovo S850 from their new european retail shops or from other distributors, you probably are in the same situation as I was a few days ago.

Doesn't matter the reasons, you probably got annoyed (as I am) of those HUNDREDS of Lenovo and Google useless apps. Maybe you have tried to root it from a custom recovery, such as TWRP (which is the only one I have found anywhere for this phone) but you failed when you probably saw that it's touchscreen doesn't respond. I know I have tried all of those and a few more but no succes.

Well, last saturday, as my final attempt, I searched once more the web to find something that could help me root it. I have found on Lenovo forums (russian forum) that there's a modified boot.img for this very phone. I have downloaded it, flashed it thru FlashTool, booted the phone and attached it to my PC with USB Debugging switched ON. After typing "adb shell" in the command prompt, I had the surprise to see "root@S850:/ #" as a result instead of that annoying "$". Well, it's time for attack!

THE METHOD DESCRIBED BELOW PROOVED TO BE SUCCESSFULL ON A LENOVO S850 Smartphone running Android 4.4.2, ROW Firmware S850_ROW_S211_140923 (lastest)

*What You Need*

1. Your Unrooted Android Device.

2 .Windows operated PC.

3. ADB Drivers installed on your PC. You can find them in Flashtool.rar or ADB.rar. Just plug in your switched-off phone and point installation wizzard to the folder.

4. The above mentioned archives: Flashtool.rar and ADB.rar. You have to download them both and extract them to your harddrive, they contain all the tools and resources needed.

*Steps*

1. Open Flash_tool.exe located in FlashTool folder you just extracted. In Flash tool, make sure that "DA DL All With Check Sum" is checked, "USB Mode" and "DA Download All/Speed/Force To High Speed" from Options tab are cheched (screenshoot bellow).

2. In Flash Tool click on "Scatter-loading", navigate to FlashTool folder, then target_bin and choose "MT6582_Android_scatter". It should load just " BOOTIMG". Well, now hit Download (with phone switched off and disconnected), wait for the progress bar to show 0% and connect the phone (still swiched off). It should start flashing boot.img on the phone and, after all is done, a green circle "OK" window should announce a successfull flash. Disconnect phone, switch it on, wait for it to load and reconnect it to PC (AFTER you checked USB debugging in USB computer connection that appeared).

3. Rooting time! Open ADB folder and double-click CMD. You have to put/extract ADB folder to C: drive, otherwise adb commands won't work (and you'll have to manually change directory in command prompt and point it to ADB folder). Now you have to insert the following commands in the window you just opened. Here we go:

adb devices (with this command you can see if the device is properly installed. if it is ok, it should be listed like "A6EAYPRSA6UGGIT4 device". if anywhing else, reinstall ADB Drivers)
adb shell
mount -o remount,rw /system
mkdir /system/bin/.ext
exit

adb push su /system/xbin/daemonsu
adb push su /system/xbin/su
adb push su /system/bin/.ext/.su
adb push Superuser.apk /system/app/Superuser.apk
adb push install-recovery.sh /system/etc/install-recovery.sh
adb push 99SuperSUDaemon /system/etc/init.d/99SuperSUDaemon

adb shell
chmod 0777 /system/bin/.ext
chmod 06755 /system/bin/.ext/.su
chmod 06755 /system/xbin/su
chmod 0755 /system/xbin/daemonsu
chmod 0755 /system/etc/install-recovery.sh
chmod 0755 /system/etc/init.d/99SuperSUDaemon
chmod 0644 /system/app/Superuser.apk
reboot

A successful session should look like this:

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\ADB>adb devices
* daemon not running. starting it now on port 5037 *
* daemon started successfully *
List of devices attached
A6EAYPRSA6UGGIT4 device

C:\ADB>adb shell
root@S850:/ # mount -o remount,rw /system
mount -o remount,rw /system
root@S850:/ # mkdir /system/bin/.ext
mkdir /system/bin/.ext
root@S850:/ # exit
exit

C:\ADB>adb push su /system/xbin/daemonsu
3919 KB/s (125424 bytes in 0.031s)

C:\ADB>adb push su /system/xbin/su
3919 KB/s (125424 bytes in 0.031s)

C:\ADB>adb push su /system/bin/.ext/.su
3919 KB/s (125424 bytes in 0.031s)

C:\ADB>adb push Superuser.apk /system/app/Superuser.apk
3961 KB/s (4120012 bytes in 1.015s)

C:\ADB>adb push install-recovery.sh /system/etc/install-recovery.sh
0 KB/s (629 bytes in 1.000s)

C:\ADB>adb push 99SuperSUDaemon /system/etc/init.d/99SuperSUDaemon
0 KB/s (55 bytes in 1.000s)

C:\ADB>adb shell
root@S850:/ # chmod 0777 /system/bin/.ext
chmod 0777 /system/bin/.ext
root@S850:/ # chmod 06755 /system/bin/.ext/.su
chmod 06755 /system/bin/.ext/.su
root@S850:/ # chmod 06755 /system/xbin/su
chmod 06755 /system/xbin/su
root@S850:/ # chmod 0755 /system/xbin/daemonsu
chmod 0755 /system/xbin/daemonsu
Unable to chmod /system/xbin/daemonsu: Read-only file system
root@S850:/ # mount -o remount,rw /system
mount -o remount,rw /system
root@S850:/ # chmod 0755 /system/xbin/daemonsu
chmod 0755 /system/xbin/daemonsu
root@S850:/ # chmod 0755 /system/etc/install-recovery.sh
chmod 0755 /system/etc/install-recovery.sh
root@S850:/ # chmod 0755 /system/etc/init.d/99SuperSUDaemon
chmod 0755 /system/etc/init.d/99SuperSUDaemon
root@S850:/ # chmod 0644 /system/app/Superuser.apk
chmod 0644 /system/app/Superuser.apk
root@S850:/ # reboot
reboot

C:\ADB>

If anything went right, your phone should be rooted. Mine was (and I'm not a programmer). Here's some screenshoots I made:

Before...

... and After

There's a few screenshoots with SuperSU in action after successful rooting:

I'm not the author of this method, I've just collected and tested different things on my OWN phone until I was able to root it. Use it on your own risk!