Connect the SD card to your computer by using an external card reader.For more information, type: 'man newfs_msdos'. Hint: to re-enter a previous command you typed, hit the up arrow repeatedly. Make sure you enter the command with the correct case and spacing. If you get some instructions on the newfs_msdos command with a new prompt, the command did not execute. You can verify this in Disk Utility after mounting the SD Card. You can remove the SD Card it is now formatted in FAT 16. below), the command executed successfully. If you get just a new prompt (or a prompt with some warnings, e.g. newfs_msdos -F 16 /dev/disk5s1 and hit the Return key. Newfs_msdos -F 16 (path to SD Card device)/(SD Card device number)

Again, make sure you type the correct device number and path as you can very easily erase your hard drive in UNIX. Be careful to type the following command with the correct letter case and spacing. The desktop icon of the SD card will disappear.

In Disk Utility, highlight the SD Card device and click Unmount at the top, not Eject.

You should see the SD Card device number listed. Then type ls (with a lower case L) and Return key.

In a terminal window: type cd /dev and hit the Return key to go to the dev directory. For my Mac, the path to devices is '/dev'.Once you have the device number of the SD Card, you need the path to the SD card device.Note this number as it will change by itself to 'Untitled'. The SD Card Volume Name will change to the UNIX device number e.g.

Select Volume Format: MS-DOS (FAT) Click Erase… > Click Erase.Highlight the SD Card device (upper icon), not the SD Card volume (lower icon).In order to find the card's device name do the following:.Format a Flash Card as FAT16 in Mac OS X Finding the card's device name

How to format sd card in mac