what is "Apple Built In SDXC Reader.dmg"

While cleaning up the hard drive on my MacBookPro I've encountered a large (128 Gb) dmg file. It won't mount and I get a "no mountable file systems" warning message. I am wondering what on earth this file could possibly be. 2012 MBP running Catalina.

MacBook Pro 13″, macOS 10.13

Posted on Sep 8, 2023 3:59 PM

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4 replies

Sep 9, 2023 5:55 PM in response to generousmedium

Hey generousmedium,


A .dmg file is a container file typically housing an installer. Apple's SD slot reader, if your Mac has one doesn't need a dmg file as all the necessary software is built into macOS.


Do you recall creating a custom .dmg in the past? Create a disk image using Disk Utility on Mac - Apple Support


We can say this does not appear to be a part of the core macOS files. It's likely something that was created after the fact.


Cheers!

Sep 10, 2023 5:41 AM in response to generousmedium

Thanks for the response, folks. I'm going to retrieve the lost bytes. 128 gigs ain't chicken feed. As far as my having made it myself, and subsequently having forgotten about it, that's quite possible. I suppose it's the size of the darn thing that gives me pause! But it's not as if I haven't lost mountains of data over the years.

Thanks, again for chiming in!

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what is "Apple Built In SDXC Reader.dmg"

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