I can successfully make bootable USB pendrives. Recently however, I noticed that the unused space on the drives is wasted.

For example, if I use a 16GB USB stick and load 16.04 onto it via the Start Disk Creator tool, I get a USB stick with about 14GB unused (and unusable).

I tried formatting the blank space using Gparted, but I get the following error:

The driver descriptor says the physical block size is 2048 bytes, but Linux says that it is 512 bytes.

Is there a way to format the unused space and make use of it?


2 Answers 2


So I finally found the answer after searching for a year!

When you get this warning message after using USB Startup Disk Creator

"The driver descriptor says the physical block size is 2048 bytes, but Linux says that it is 512 bytes." Means that the dd command in behind the nice GUI forgot to specify the bs=2048 option.

First identify which drive letter the USB stick has received from the kernel

sudo parted --list

For example this USB drive is on Device Serial Disk h: (/dev/sdh)

Model: KINGSTON DataTraveler G3 (scsi) Schijf /dev/sdh: 4001MB

Use the information to wipe all the partition tables and data from the drive


sudo wipefs --all /dev/sdX

Make sure that you have chosen the correct USB stick for the value of X so you don't accidentally wipe your harddrive/SSD


It's not that the unused space is wasted. The USB disk has been corrupted by USB Startup Disk Creator. For some reason USB Startup Disk Creator has become CD-ROM creator. It writes your USB-Stick to iso9660 format which is only intended for CD-ROM's. Since new computers don't come with CD-ROM players or writers anymore this is a regression bug and has been reported here: https://bugs.launchpad.net/ubuntu/+source/usb-creator/+bug/1708881

  • Most linux distros provide hybrid iso files, which work both to create DVD boot disks and USB boot drives. This means that there will be an iso 9660 file system in the USB drive. This is not wrong, it is a working system for a live-only drive and installer drive. The problem is that some tools do not understand, what it is, and complain, that is is corrupted. Fortunately there will be a new version of gparted in 17.10, which can recognize such drives. -- You can restore such a boot drive to a standard storage device with mkusb, help.ubuntu.com/community/mkusb/wipe
    – sudodus
    Oct 15, 2017 at 12:43
  • See more details at this link, askubuntu.com/questions/962727/…
    – sudodus
    Oct 15, 2017 at 14:47
  • executing sudo wipefs --all / /dev/sdb I got : probing initialization failed: Device or resource busy
    – Carmine
    May 12, 2018 at 8:14
  • I was able to unallocated the "free" space that was read-only but not able to format via Ubuntu, cause where is wrote the usb-ubuntu live was blocking it. From W7 instead it allow me to format the free space (14 Gb) and rescue all the free space. This way I lost only 2 GB.
    – Carmine
    May 12, 2018 at 8:44

Some startup disk creators like universal usb installer can create some space to put documents and other programs, that stay after rebooting from the live usb. You can set this size and use more of your usb that way.

I don't know of any way to put files alongside your bootable iso and still have it work.

Resizing the partition probably won't make a difference, and the startup disk creator chooses a partition table that apparently only allows for 1 primary partition, so i seem to be unable to create another partition in the unnalocated space. It seems that the only option is to use universal usb installer (or any other live usb creator that supports this) to create larger space for persistent storage.

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