FDISK command: How To Fix A Broken USB Drive Using Linux

Introduction

Sometimes when people create a Linux USB drive they find that the drive seems to become unusable.
This guide will show you how to format the USB drive again using Linux so that you can copy files to it and use it as you ordinarily would.
After you have followed this guide your USB drive will be usable on any system capable of reading a FAT32 partition.
Anybody familiar with Windows will notice that the fdisk tool used within Linux is much like the diskpart tool.

Delete The Partitions Using FDisk

Open a terminal window and type the following command:
sudo fdisk -l
This will tell you which drives are available and it also gives you details of the partitions on the drives.
In Windows a drive is distinguished by its drive letter or in the case of the diskpart tool each drive has a number.
In Linux a drive is a device and a device is handled much like any other file. Therefore the drives are named /dev/sda, /dev/sdb, /dev/sdc and so on.
Look for the drive which has the same capacity as your USB drive. For example on an 8 gigabyte drive it will be reported as 7.5 gigabytes.
When you have the correct drive type the following command:
sudo fdisk /dev/sdX
Replace the X with the correct drive letter.
This will open a new prompt called "Command". The "m" key is very helpful with this tool but basically you need to know 2 of the commands.
The first is delete.
Enter "d" and press the return key.

If your USB drive has more than one partition it will ask you to enter a number for the partition you wish to delete. If your drive only has one partition then it will be marked for deletion.

If you have multiple partitions keep entering "d" and then enter partition 1 until there are no partitions left to be marked for deletion.

The next step is to write the changes to the drive.
Enter "w" and press return.
You now have a USB drive with no partitions. At this stage it is completely unusable.

Create A New Partition

Within the terminal window open fdisk again as you did before by specifying the name of the USB device file:
sudo fdisk /dev/sdX
As before replace the X with the correct drive letter.
Enter "N" to create a new partition.
You will be asked to choose between creating a primary or extended partition. Choose "p".
The next step is to choose a partition number. You only need to create 1 partition so enter 1 and press return.
Finally you need to choose the start and end sector numbers. To use the whole drive press return twice to keep the default options.
Enter "w" and press return.

Refresh The Partition Table

A message may appear stating that the kernel is still using the old partition table.
Simply enter the following into the terminal window:
sudo partprobe
The partprobe tool simply informs the kernel or partition table changes. This saves you having to reboot your computer.
There are a couple of switches you can use with it.
sudo partprobe -d
The minus d switch lets you try it without it updating the kernel. The d stands for dry run.

This is not overly useful.

sudo partprobe -s
This provides a summary of the partition table with output similar to the following:

/dev/sda: gpt partitions 1 2 3 4
/dev/sdb: msdos partitions 1 

Create A FAT Filesystem

The final step is to create the FAT filesystem.
Enter the following command into the terminal window:
sudo mkfs.vfat -F 32 /dev/sdX1
Replace the X with the letter for your USB drive.

Mount The Drive

To mount the drive run the following commands:
sudo mkdir /mnt/sdX1
sudo mount /dev/sdX1 /mnt/sdX1
As before replace the X with the correct drive letter.

Summary

You should now be able to use the USB drive on any computer and copy files to and from the drive as normal.