Ubuntu – How to format a Windows Pen drive

If you are completely, positively, SURE that you want to erase the current contents of your pen drive, then you can try the dd command as described below.

First, check one last time that /dev/sdb refers to the pen drive you want to erase. As another answer has pointed out, you want to have no doubt that you are erasing the correct device. (I would probably run the command sudo fdisk -l as an extra check.)

The dd command below should write zeros to the first MiB of the pen drive which will erase any partition table. This should completely remove any partitioning.

sudo dd if=/dev/zero bs=1M count=1 of=/dev/sdb

If you decide you want to write zeros to the entire device, just omit the count=1 parameter. This will take longer, of course. How much longer depends on the size of the pen drive you are erasing.

sudo dd if=/dev/zero bs=1M of=/dev/sdb

After you have erased the partition table with zeros, you can partition the drive. I would do this using gparted simply because I am familiar with that tool and know how to use it.

Here is how I would do it.

• If gparted is not already available on your system, install it. You could, for example, use the command below.
  sudo apt-get update && sudo apt-get -y install gparted
• Start gparted, entering your password when it is requested.
• Perform the following steps.
  1. Select the pen drive as the current gparted device.
  2. Select the free space region on the pen drive.
  3. Select Create Partition Table in the Device menu and create an MS-DOS style partition table.
  4. Select New in the Partition menu to create a new primary partition on the pen drive. Or if you prefer, you could close gparted at this point and use fdisk to partition the pen drive.

Note:

If you wanted to do this in Windows I suggest using the DISKPART command in a command window. Once in DISKPART select the correct disk and then issue the command CLEAN.

(You can issue the command HELP CLEAN while in DISKPART form more information about what the command does.)

If the USB was once writable and is now no longer, this suggests 3 things in my mind:

1. A hardware switch on the device has been toggled.

   If this is the case, the simple fix would be to find that hardware switch (they can be really subtle), and toggle it.

2. An "unclean" unmount occurred, such as pulling the USB out of the slot before the OS finished writing data to it

   To save the life of devices, and to improve performance, writes to most storage mediums are buffered -- including USB drives. In essence, this means then unless you tell the operating system to eject/unmount the USB drive, you have no guarantee that all data has been written. Further, most filesystems have flags to indicate when they've been mounted and unmounted: always tell the OS you're going to remove the drive ("eject", "unmount", "turn off") before you pull it out of the slot.

   Consequently, if simply checking and fixing the filesystem does not work, then you could try the ham-fisted approach of copying your data temporarily somewhere else, reformatting your USB drive, and then copying your data back. By reformatting, you're completely overwriting what was there, so the OS/filesystem will have no recollection the USB drive/filesystem was readonly before the format.

   One detail on repairing the filesystem. Make sure it's not mounted first. Your set of commands implies it's mounted. So:

   sudo umount /dev/sdb1

   sudo dosfsck -a /dev/sdb1

3. The USB disk itself is dying, and the embedded firmware is protecting you from losing any data.

   If the USB uses flash-based storage, it's possible that you have written to the device enough times that it is now unable to write anymore. Writing to flash-based is a destructive process, and each sector can only take so many rewrites. Many drives will "hide" this fact, by internally having much larger storage (say 16G of total write space), but only present to the OS as a smaller amount (say 2G). As each sector begins to wear out, the firmware will automatically move the data to a new unused sector. After too many writes, however, there will be no more usable storage, and smart firmware implementations will lock the drive to prevent data loss. At that point, your only option would be to copy the data to a new flash drive.