First of all download the Linux version of Flash tool from Flashtool website.
http://www.flashtool.net
Then ensure that you have libusb-1.0 is installed. 64bits system needs the both 64bit and 32bit. If you don't have it, simply download it using the package manager of your distribution version.
Now type this command the configure some USB settings for Flashing interface
Settings are saved inside /etc/udev/rules
create new file for settings using terminal/command line as root (sudo/su followed by password for root)
cp /etc/udev/rules.d/70-persistent-net.rules /etc/udev/rules.d/80-persistent-usb.rules
then open the file by
vi /etc/udev/rules.d/80-persistent-usb.rules
paste the following lines to the file.
SUBSYSTEM=="usb", ACTION=="add", SYSFS{idVendor}=="0fce", SYSFS{idProduct}=="*", MODE="0777"
save the file and close it.
then go to the place where you saved the extracted Flashtool-xxxxxx.tar.7z by using
#cd <place_where_extracted_files_saved>
Run the program using
#./FlashTool
wait until "Cloning devices from github project" or any other waiting window closes.