Can't erase USB in Disk Utility

Question

Level 1

6 points

Can't erase USB in Disk Utility

Hi.

Twice now, with two different USBs, something has happened so that I can't erase the USB. Even trying to erase the free space doesn't work. It happened, I think, when I pulled a USB from the port without ejecting it. I had to do that because Finder wouldn't let go of a file (app) that it had been unable to completely write onto the USB. It means I have two USBs that have almost nothing on them but almost no free space.

Does anyone have any suggestions?

Many thanks.

Mac OS X (10.5.8)

Posted on Nov 1, 2015 1:53 AM

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Answer 1

den.thed

Level 10

91,582 points

Nov 1, 2015 6:25 AM in response to Kiwisda

1. How are the external drives formatted...?

control (right) click on the drive icon and select Get Info

2. What files and how did you try to copy the files to the external drive...?

did you try copying with Finder or did you allow Time Machine to use the external drive

3. To remove files on external drives, open the drive, move the files to the trash and empty the Trash.

before disconnecting your external drive, you must empty your OS X Trash to regain that space on the drive

4. If you want to completely clear/wipe everything from the external drive, you will need to reformat it using Disk Utility.

setting up an external drive (Partition Map Scheme and Format) depends on what and how you plan to use the external drive

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Answer 2

Kiwisda Author

Level 1

6 points

Nov 1, 2015 12:18 PM in response to den.thed

Thanks for the reply.

I was copying an app file to the USB. About 1.6GB onto a virtually empty 2 GB disk. When about 1.4GB had copied it stopped and said it couldn't copy any more because it couldn't read some of the file. So I then tried to close the message window. That window wouldn't close. I tried to trash the incompletely loaded file. It wouldn't do that either. I tried to eject the stick. It wouldn't eject. So I pulled it out. When I did so, the message window closed. I then put the stick back into the computer, opened DU to do a disk erase. But it won't erase. It won't unmount either.

It's formatted as MS-Dos (FAT).

I was copying simply by dragging the app file from the app folder straight onto the disk.

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Answer 3

den.thed

Level 10

91,582 points

Nov 1, 2015 1:09 PM in response to Kiwisda

Sorry for all the questions. What App...App File...?

Sounds like you need to completely clear/wipe the external drive and make it Mac OS X compatible. If your running 10.5 thru 10.10 use the following directions to Partition and Format the external drive for OS X.

1. Connect the External HD and open Disk Utility in your Utilities Folder.

2. Highlight the External Drive in the list of drives and select the Partition tab.

3. Under Volume Scheme select 1 Partition and click on the Options... button.

4. Select GUID Partition Table in the drop down window and click OK.

5. Set the Format to Mac OS Extended (Journaled), name it and click the Apply button.

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Answer 4

Kiwisda Author

Level 1

6 points

Nov 1, 2015 1:30 PM in response to den.thed

It was an iPhoto app.

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Answer 5

Kiwisda Author

Level 1

6 points

Nov 1, 2015 4:35 PM in response to den.thed

Thank you for your help. I am now in another location and using my MacBook (El Capitan). Previously I was using my iMac (Yosemite). On the iMac, I couldn't erase it. The instructions you gave me were for up to OS X 10.10, and DU is different in 10.11. So I couldn't try them. But I tried simply the Erase function in 10.11 and it worked! I can't wait to get home and see if I can also erase my other USB which is presently useless to me.

Much appreciate your advice and the things I learn from you and others.

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Answer 6

den.thed

Level 10

91,582 points

Nov 1, 2015 4:40 PM in response to Kiwisda

You are welcome!

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