Unlock Xperia S bootloader from Ubuntu 12.04

Introduction

I tried to unlock bootloader from Windows 8 and in vain. Windows 8 installed some drivers for fastboot and never allowed an option

Now it became interesting, I came to my Ubuntu system and started exploring

After getting the unlock key from sonymobile, I tried in Windows 8. It did not work, then came to Ubuntu 12.04 and it worked happily.

To get the unlock key for your Xperia S (or some other xperia mobile) follow upto 7 steps

http://unlockbootloader.sonymobile.com/instructions

From 8th step, instructions for applying the unlock key to unlock your phone in Windows, but no explanation of how it is done in Ubuntu. So here I explain what I tried and what worked

Before going into what I am talking, see my earlier article on how to install Flashtool in Ubuntu 12.04

and come here. In brief, download flashtool, extract. Have ia32-libs installed and have udev rules 

SUBSYSTEM=="usb", ACTION=="add", SYSFS{idVendor}=="0fce", SYSFS{idProduct}=="*", MODE="0777"

Using Fastboot from Ubuntu to Unlock 

After extracting Flashtool, go into flashtool folder from file browser, it should look like

Double click x10flasher_lib which should take you inside x10flasher_lib folder. 

[[[Note if you don't have open in terminal, proceed after ending square brackets if you already have this or if you use Linux Mint

If you do not have Open in Terminal install it from command line using 

sudo apt-get install nautilus-open-terminal

Logout and login again to enable nautilus open terminal. If you have Linux Mint, this is already installed and enabled and you do not need to do this!!]]]

Now from inside x10flasher_lib right click blank space and select Open in Terminal

You should be inside x10flasher_lib in command line. 

Become root (this is very important)

sudo su

Backup your phone data (contacts, sms, images, songs ...), switch off phone

Entering your phone into fastboot mode 

Step 1:

After switching off, Connect one end of your usb cable to phone and do not plug other end of usb cable to your PC/Laptop

Step 2: 

Press and hold Volume up button and plug other end of usb cable into your ubuntu system (Your phone led should glow in blue color)

Step 3: 

From inside x10flasher_lib directory as root, execute the following command to test the version

            ./fastboot.linux -i 0x0fce getvar version

You can see from the above screenshot, fastboot.linux displays version as 0.5. It means we are good to go and unlock the phone

Step 4:

To unlock your phone (fingers crossed), do this (paste the unlock key you got from email after 0x)

          ./fastboot.linux -i 0x0fce oem unlock 0x

It should unlock, now unplug usb cable and switch on your phone.

Step 5:

Happily install recovery and install custom ROM of your choice, 

for e.g, I tried this combination and it worked!

Install Advanced Stock Kernel and install XTXperience 7

http://forum.xda-developers.com/showthread.php?t=1729280

http://forum.xda-developers.com/showthread.php?t=1931325

For installing custom kernel, you can run Flashtool in fastboot mode

From here, it is fairly straightforward, flash the kernel using "Select Kernel to Flash" button

If you flash Advanced Stock Kernel, it will be prerooted and have recovery installed. Custom rom can be installed from recovery