create image file and bootable cd

Firstly, use dd to create image file:

$ dd if=/dev/fd0 of=my.img bs=10k count=144

Secondly, find out a file named boot.img or boot.cat in your system, and make the ISO file:

$ mkisofs -r -b my.img -c boot.img -o my.iso /output_directory

The optional R/W CD erasing:

$ cdrecord dev=0,0,0 blank=fast

Finally, burn the ISO to the blank CD:

$ cdrecord -v speed=12 dev=0,0,0 -data my.iso