!!!!Warning unlocking bootloader may brick or void your device warranty use at you own risk!!!!!
1.Turn on usb debugging in developer options
2. poweroff device then press and hold volume – key to enter fastboot
3.Connect to any linux system which has fastboot installed.
[02:25 root@server .../cipher/Desktop]# fastboot --version fastboot version e7195be7725a
4.Check the device if its detected by fastboot
[02:19 root@server .../cipher/Desktop]# fastboot devices e4a26a61 fastboot
5. Unlock the boot loader
[02:21 root@server .../cipher/Desktop]# fastboot oem unlock ... OKAY [ 0.030s] finished. total time: 0.030s
6.Reboot the device
[02:21 root@server .../cipher/Desktop]# fastboot oem unlock ... OKAY [ 0.030s] finished. total time: 0.030s
7.To relock the bootloader use lock command.
[23:47 root@server .../cipher/vagrant]# fastboot devices e4a26a61 fastboot [23:47 root@server .../cipher/vagrant]# fastboot oem lock ... OKAY [ 0.032s] finished. total time: 0.032s
8.reboot the device.
[23:47 root@server .../cipher/vagrant]# fastboot reboot rebooting... finished. total time: 0.070s