I have a Centon Flash Drive that will not mount. It is not readable on the iMac nor a Windows 7 machine. The drive cannot be reformatted by the Windows or IMac usual methods that this layman tried.

In another thread about this subject I've read:

Can you get the disk identifier? In Disk Utility, select the drive and choose "Info" – it should read something like disk1 or disk2 or so. (But NOT disk0; that's your internal HD!)

Then open a terminal, and type in

sudo dd if=/dev/zero of=/dev/diskX  

(where diskX is of course the disk identifier you got earlier.)

Type in your admin password, and it should overwrite every block of the disk with 0x00 (i.e. erase it).

Then, you can format your drive.

[Please be cautious when doing this; I'm not responsible for anything if anything goes wrong ;-)]

I have OS X 10.6.8.

Will you tell me if I should try this and if yes, how do I "open a terminal"?

  • Cmd+Spacebarshould open a spotlight search. Type Terminal and press Enter Feb 14, 2016 at 6:56

2 Answers 2


If you don't feel comfortable using Terminal you could try SDFormatter from www.sdcard.org just select SD Formatter for Mac Download and agree to the terms, it is a free app. I have successfully formatted sd cards that wouldn't mount.


Yes, the above procedure should work, although note that there is no warnings or prevention methods against doing something wrong. Typing the wrong disk identifier could erase your internal disk. Have backups and be careful.

To open Terminal, go to /Applications/Utilities/ and open Terminal.app.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .