These are the instructions to root Karbonn A21 Smart (running on android 4.0) Smart Smartphone using Binary Toolkit on Windows Computer.
Requirements: Your Karbonn A21 Smart Smartphone should have at least 30-40 percent of battery to perform the rooting process.
Step 1: Download and install Karbonn A21 Smart USB Driver on your Windows Computer.
Step 2: Download and extract the Karbonn A21 Smart root files on your computer. After extracting you will be able to see the following files:
Step 3: Enable USB Debugging mode on your Karbonn A21 smartphone. To Enable USB Debugging: Settings > Developer Options > USB Debugging (Tick to enable it).
Step 4: Connect your Smartphone to the computer.
Step 5: Now, Open runme.bat (you have extracted it in Step#2).
Step 6: Once runme.bat is launched, Type 1 from the keyboard and press Enter key to begin the rooting process.
Step 7: Now, your smartphone will ask to perform Full Restore. To perform full restore, Tap on the Restore my Data to continue.
Step 8: That’s it. Now your Karbonn A21 Smart is successfully Rooted. To check whether your tab is rooted correctly, open Applications Menu, there you will be able to see a new app installed, called SuperSU. If this app exists then it means you have successfully rooted your Karbonn A21 Smart.
Optional: You can also verify the root status of your device by using the Root Checker Application.
[*] No data loss process: Your Phone Data like contacts, pictures, videos, music and etc will be not affected with this method. In short, no data loss process.
[*] Phone Warranty: If you follow the above instructions your phone warranty will be void.
[*] How to unroot? To unroot your device, Open SuperSU > Settings > Full Unroot.
[*] Karbonn Stock Firmware: If you are looking for the original Stock Firmware then head over to the Karbonn Stock Firmware Page.
[*] Karbonn USB Driver: If you are looking for the original usb driver then head over to the Download Karbonn USB Driver Page.