Actually, this is just for my notes, but maybe it’s useful for someone else. here’s how to format a flash drive in Ubuntu via the terminal.
1. Open a terminal and log in as sudo user
2. after that type $sudo fdisk -l to see where the flash drive is on which boot device,
whether in /dev/sdb1 or /dev/sdc1 or in /dev/sdd1 or something else.
3. Before formatting, you must first unmount it with the following command
$sudo umount “locate flsdisk”
example: $sudo umount /dev/sdb1
4. lastly type the command format
$sudo mkfs.vfat /dev/sdb1
Congratulations, your flash drive has been formatted.