First of all, I am a newbie to Android. I am using Ubuntu Gnome 14.10 to run all the commads.
I am trying to unlock the bootloader of my Lenovo A536 (stock Android 4.4.2 aka KitKat). Here is what I am trying to do:
$ adb devices # lists the devices, apparently working
List of devices attached
$ adb reboot bootloader # no terminal output; phone enters fastboot
(there is written '=> FASTBOOT mode...' in the
$ fastboot oem unlock # and here it stops without exiting; I have to force quit
... the fastboot by holding the phone power button for over
10s and then the command in terminal ends'
Before doing this I checked the USB debugging in the Developer’s menu.
lsusb output (part of it) while the phone is connected to pc and booted in fastboot:
Bus 002 Device 064: ID 0bb4:0c01 HTC (High Tech Computer Corp.) Dream / ADP1 / G1 / Magic / Tattoo
Update #2 I found out that after installing a USB VCOM Driver on a Windows machine I was able to flash TWRP 2.7.1. I think Linux somehow does not recognise my phone.
Here is the link with tutorial to flash TWRP 2.7.1 using Windows. Note that before running SP Flash Tool, you must connect phone without battery to the computer, and after selecting the scatter file, you must insert battery into phone, otherwise SP Flash Tool would not flash anything.