Q. How do I use dd command to make a diskette?

A. dd is use to copy a file, converting and formatting according to the options.

Since everything is considered as a file under Linux you can write files to a diskette with dd command itself.

For example if you want to write boot.img (Linux boot disk image) file to a diskette:

Insert a disk but do not mount

Type the following command as root user:
# dd if=disk.img of=/dev/fd0 bs=1440k

Read man page of dd for more information.