If you are getting that message it means that your drive usb/hdd has a faulty partition table, you can fix this by plugging your drive to any windows based computer and fix it via CMD, there are like 4 simple commands that will allow you to fix and recreate the main partition on any USB drive!! This is usually consequence of using your USB drives on both platforms, the file sistema and partition tables get messy and thats when you get stuck... you can google how to recreate the partitions on your drive...
Dec 25, 2016 6:19 PM
May 21, 2017 So I set it up with Mountain Lion on the SSD and it was working well. Then I decided to clone it to the HDD using Carbon Copy Cloner. I also got it to make a recovery partition on the HDD. In Disk Utility, it looked fine. I then booted it off one of the recovery disks to check. In Disk Utility, the two disks appeared in red but were otherwise. Since this card contains three partitions with one being a blessed bootable partition, I would like to see if there are any ways to get my Mac to generate these for me. Since disk-utility archived the full SD card with partitions, I would assume is has a way to recover it going the other way.
Mac Disk Utility Sd Card Waiting For Partitions To Activate Another
To encrypt the card, insert it into your reader and attach the reader to the machine. Once the card is recognized, open the Disk Utility app (found in Launchpad). You should see the card listed in.