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the8thark

macrumors 601
Original poster
Apr 18, 2011
4,628
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I am trying to format a micro SD card on my Mac via a micro sd SD card adapter. The thing keeps saying "can't modify partition map" in disk utility.
Does anyone know what the fix is for this so I can actually format the card and start writing to it?
I tried to format the SD card itself (called disk3s1) with no luck. Says "can't modify partition map"

Would erasing/formatting the Micro SD card reader fix the issue and if so which scheme should I use?

FSs6wg8.jpg


I am at a loss here of what I can do to fix the issue. Does anyone have any ideas here?

[edit] I tried to format the card via terminal and I get the "Couldn't open device" error.
So I am really at a loss of what to do here.
 
Last edited:
I suggest that you use the SD Memory Card Formatter distributed by the SD Association itself. After all, they're the group that created the SD Card specifications. You can get it for Windows or macOS here:

https://www.sdcard.org/downloads/formatter/

Also, make sure that you've no accidentally slipped the write protect slider, on the card, to the write protect position.
 
I am trying to format a micro SD card on my Mac via a micro sd SD card adapter. The thing keeps saying "can't modify partition map" in disk utility.
Does anyone know what the fix is for this so I can actually format the card and start writing to it?
I tried to format the SD card itself (called disk3s1) with no luck. Says "can't modify partition map"

Would erasing/formatting the Micro SD card reader fix the issue and if so which scheme should I use?

FSs6wg8.jpg


I am at a loss here of what I can do to fix the issue. Does anyone have any ideas here?

[edit] I tried to format the card via terminal and I get the "Couldn't open device" error.
So I am really at a loss of what to do here.
Boot into recovery mode and try erasing the SD card.
 
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