1. Find the name of the SD card. (ex> /dev/sdd in my case. You must enter your own SD card device name.)

   sudo fdisk -l

If SD card is already mounted, unmount it.

sudo umount [/dev/sdd]

1. Remove partition.

sudo fdisk [/dev/sdd]

You can delete partition by entering d. (Refer to following info.)

m: help. d: delete partition. p: print current partition information. n: make new partition. w: save and exit.

1. Format SD card.

sudo mkfs.ext2 [/dev/sdd]

1. Mount your SD card.

sudo mount [/dev/sdd] [mount directory]