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I use a microSD card in my macbook air for additional storage, using a flush adapter (homemade, similar to the nifty minidrive).

To save battery when I'm not using it, I disabled auto-mount using /etc/fstab. But sometimes, I accidentally eject it instead of unmounting (because that's what the finder gui does).

After it's ejected, the only way I know to remount is to take the card adapter out and put it back in. Since it's flush, I need a paperclip to take it out.

So I need a way to re-enable the card reader without having to re-insert.

In Windows, this is possible using the devcon command-line tool from microsoft, or going to device manager, disabling and enabling the card reader.

There has to be a way to do this, so please don't answer just saying it's not possible.


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I appreciate this isn't what you want to hear, but unfortunately, I don't think there is a way to remount once you've ejected a disk (either through Finder, Disk Utility or using diskutil). As you say, if you unmount this disk (rather than eject) using diskutil unmountDisk, for example, then you can simply remount it again afterwards with diskutil mountDisk. That said, take a look at this question which suggests and alternative app and (in the comments) a way to do it using unloading kexts –  binarybob Aug 31 '12 at 9:13
Thanks for the kernel module unload/reload idea, that makes perfect sense. I don't know why I didn't remember about that, it is equivalent to the Windows way. –  CoolkcaH Sep 1 '12 at 12:24
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2 Answers

up vote 3 down vote accepted

On Mountain Lion with built-in SD readers:

sudo kextunload -b com.apple.driver.AppleSDXC
sudo kextload -b com.apple.driver.AppleSDXC
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Type this in terminal:

sudo kextunload /System/Library/Extensions/AppleStorageDrivers.kext/Contents/PlugIns/AppleUSBCardReader.kext; sudo kextload /System/Library/Extensions/AppleStorageDrivers.kext/Contents/PlugIns/AppleUSBCardReader.kext

This will unload and load the card reader kernel drivers, and it will appear in diskutil again.

Thanks to binarybob for the pointers.

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