I made a backup of the 16gb microSD card (installed with NOOBS) for a Raspberry Pi 3 and saved it to my Mac using:
sudo dd if=/dev/disk2 of=~/Desktop/raspberrypi.dmg
Then, I took a 64gb microSD card, formatted it to exFAT using the SDFormatter tool (while turning Logical Address Adjustment on), and formatted it to FAT32 and unmounted it using:
sudo diskutil eraseDisk FAT32 RASPBIAN MBRFormat /dev/disk2 diskutil unmountDisk /dev/disk2
Now I got hasty and accidentally ran the same dd command as above (I should have ran
sudo dd if=~/Desktop/raspberrypi.dmg of=/dev/disk2). This copied the blank 64gb microSD to the raspberrypi.dmg file until my Mac ran out of memory. So now the .dmg file is corrupted.
Since I created the first copy of the image, I made some changes to the 16gb microSD card and completely filled up its memory. I cloned its image to my Mac again and followed the same process to transfer it to my 64gb card. The start screen still shows up and I can enter recovery mode by pressing shift on startup. However, if I let it go on its own it brings me to a blank screen with only a blinking underscore. Any ideas of how to fix this?