Can't reformat USB flash drive - disk won't unmount

[krs]

I have a 32 GB USB drive I'm trying to reformat to FAT32.

It's Mac formatted now but it's going to a friend who doesn't use a Mac.

When I try to erase to reformat, disk utility tells me that the disk will not unmount.
Tried it several times using disk utility.

Is there a way to force the unmount other than using terminal - I really don't like using terminal; always nervous that I make a mistake typing in a command and really screw things up.

 

[IWT]

Hi krs

I hope I'm understanding you.

Your 32GB USM mounts okay?
You then open Disk Utility (DU), see the USB?

Now, then you want to reformat the USB, are you clicking on the Main volume or the indent beneath it? As in the screenshot below, are you clicking on "USB Flash Memory" or the indent "IWT"?



This makes a difference. It should be the "IWT" indent.

Then try the reformat.

Then "Unmount".

Please post back.

Ian

 

[krs]

Hi krs

I hope I'm understanding you.

Your 32GB USM mounts okay?

Yes

You then open Disk Utility (DU), see the USB?

Yes

Now, then you want to reformat the USB, are you clicking on the Main volume or the indent beneath it? As in the screenshot below, are you clicking on "USB Flash Memory" or the indent "IWT"?

On volume, ie indent "IWT"

Then try the reformat.

Then "Unmount".

All the times I reformatted any disk on any Mac, I would just click on "Erase" and pick the formatting I want.
Did the same thing here, the process starts trying to "unmount" the disk and then after a while I get the ""Can't unmount" error message

Tried the "unmount" this time first and then "erase", ie two steps - and that worked...thanks

Is that a change Apple made between SL and ElCap?
I have to try some other external drives on ElCap, but I never had to go through that two-step process before, selecting "Erase" would always automatically do the unmount process as part of the Erase and reformat process.

All is good - thanks again.

 

[ferrarr]

I have had this happen sporadically, what I do is, Unmount before formatting.


Bob -

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