Make bootable usb on Linux (dell bios/firmware upgrade)

1. use lsusb, lsblk to check USB device

2. use gparted to prepare thumbdrive as FAT32 and FORMAT

3. use unetbootin to write .iso (May you need to mount /dev/sdbX)

If you see below warning dialor. You need to mount .i.e.  mount /dev/sdb1 /mnt/sdb1