Formatting SD Cards

MultiMedia Cards (MMCs) are automagically mounted after insertion. Formatting them is harder.

After finding that a 128MB MMC was reporting ~20MB total space, something was wrong and it was suggested to me that it should be reformatted. But I didn't know how. I knew the filesystem was FAT, but FAT what? FAT12? FAT16? FAT32? Was there a format option in Ubuntu?

I couldn't find a tool to format the card, so I listed my mounted devices and saw:

/media/HP43xCARD /dev/mmcblk0p1 on /media/HP43xCARD type vfat (rw,nosuid,nodev,quiet,shortname=mixed,uid=1000,gid=1000,umask=077,iocharset=utf8)

And the space reported as:

/dev/mmcblk0p1 122912 108064 14848 88%

So a shot in the dark with mkdosfs /dev/disk/by-label/HP43xCARD reveals a card that has a total capacity of 128MB.

Searching for "formatting cf cards" or "formatting sd cards" turns up nothing useful. But a search for "formatting mmcs" turns up the kernel driver documentation.