A great command in Linux is:
dd bs=4M if=file.iso of=/dev/sd<letter> status=progress && sync
where <letter> is the letter for your flash drive. Do be careful finding it, because your hard drive(s) and CD/DVD drive(s) are also among these; you can get the list with ls /dev/sd*, and also all mounted drives can be listed with mount.
Also, it does have to be run as root, so sudo as a prefix may be very helpful.