Remove all partition from USB drive

On 18.04 I've made a bootable pen drive. Now I don't need it. I want to remove the iso9660 partition.

sudo cfdisk /dev/sdb

I tried to delete (it makes) but when I want to save the changes, it fails.

Failed to write disklabel"

It isn't write protected (read-only is 0)

What else should I try?

You can use mkusb with a graphical user interface. You can select

• 'restore to a Standard storage device', or
• 'Wipe the first mibibyte'.

There are more details at the following links to Ubuntu help wiki pages

• mkusb (what it does, and how to install it)
• Postrequisites - restore the USB stick
• mkusb/wipe

If mkusb cannot solve the problem, you can analyze it, and if you are lucky solve it, according to the following link

• Can't format my usb drive. I have already tried with mkdosfs and gparted

Rather than installing any extra software (and if you're comfortable with the command line), I would suggest using the dd command.

To wipe your USB fire up the gnome-terminal and type

sudo dd if=/dev/zero of=/path/to/usb

As was pointed out in the comments, you may be better off only wipe the MBR so as not to roast the USB

dd if=/dev/zero of=/dev/<path of data drive> bs=512 count=1 seek=0

Edit: Again as stated in comments MBR is in fact not 440 bytes :facepalm:

The non-interactive sfdisk can do this from the CLI:

sfdisk --delete /dev/sdb

See man sfdisk for details.

Use gnome-disks. That is the tool I use to remove, create and format partition in my USB drives.

You can easily install it with the command

sudo apt install gnome-disk-utility