I can't format a usb, it says it has no write permissions.

Question

When I open disk utilities the erase button is in grey and can't be clicked... I've tried using terminal and disk utilities, I also triede in a pc but it still says that the problem is I don't have write permission. How can I erase everything for good and reformat my usb? is there a program that can do that?
also when I hit verify disk it says it needs to be repaired but still doesn't enables the repari button.

Answer 1

Ok try the following. In the Terminal run this command:
sudo fdisk -e /dev/disk1
You will see a prompt that looks like the following:
fdisk: 1>
At this prompt, type "auto hfs" and press Enter, and you should see the prompt now look like the following:
fdisk:*1>
Now enter the command "write," and you should see it either say "Writing MBR at offset 0" or give you the following message:
Device could not be accessed exclusively.
A reboot will be needed for changes to take effect. OK? [n]
If this message appears, type "y" and press Enter, and you will then see the "Writing MBR at offset 0" message. Now enter the command "exit" to quit the fdisk utility, and then unmount your USB drive and reattach it to the computer. At this point you should see a message stating the drive is not readable, with options to initialize, eject, or ignore the issue. Choose Initialize, and you should be good to go.
If the drive is not automatically initialized, you should at least be able to use Disk Utility to now partition and erase it for other uses. If not, then the drive may be corrupt to the point where you cannot repartition it with the Mac. In this case, you can try with a Windows PC or another system, and see if that helps restore the drive, or replace the drive.