The Debian GNU/Linux install program gives you the option of creating a boot diskette when you install Linux. You should exercise this option each time you install Linux, so that you have a fresh boot disk containing software consistent with that stored on your hard drive.
However, you can easily create a boot diskette after the installation is complete. To do so, insert a blank floppy diskette into your system's floppy drive. Log on as root and issue the following command:
For kernal, substitute the name of the file that contains the kernal you want to place on the boot disk, usually vmlinuz