Archiving Floppy Disks Using Images

by Charlton Rose

We all have a stack of floppies sitting around that none of us ever use, but which we can't bare to throw away because we know that as soon as we do, we will miss them. On top of that, we also know that the lifetime of a floppy is very short; even if you do have a place to store all your floppies, odds are good that eventually the bits on them will go bad anyway. This mini-tutorial offers a technique you can use to archive your floppies onto more durable media, such as your hard drive or a CD-ROM, in a manner that allows you to reconstruct any of the floppies at a later time.

Often, it is not enough just to back up the files on a floppy. Sometimes the exact arrangement of data blocks on the disk are important. When backing up a commercial floppy, for example, it is usually best if you can create a bit-for-bit copy of the original. The techniques illustrated in this document achieve this goal.

floppy disk images

All of the data on your floppy, including the files, the directory tables, etc. can be represented in a single file called an "image." Images are useful because they encapsulate the entire structure of a disk without regard to what is actually on the disk. Thus, images can be used to represent disks of various formats.

Unfortunately, the techniques described in this document work only with 3¹/₂ inch high density (1.44 Mb) disks. However, they can be adapted for other types of disks if you know the correct parameters. Some formats that might not work with the techniques described in this document include Macintosh and the special format Microsoft used to distribute copies of Windows 95. (If you figure out the correct parameters for these formats, let me know so that I can include them here.)

reading images

There are various commercial utilities available for DOS and Windows that can read floppy disk images. Unfortunately, I have not been able to find any of them that are free. If you use Linux, however, the process is quite easy and no commercial software is required. Simply put your disk in the drive and execute the following command:

dd if=/dev/fd0 of=floppy.img count=1 bs=1440k

Of course, you can replace floppy.img with the file name that you want the extracted image to have.

When the command completes, you will have a single file on your hard drive representing the entire disk. This file, called an "image," can be used to reconstruct the floppy at any given time. From this point, you just need to keep the file on your hard drive, write it a CD-ROM or tape, or preserve it in any other way you feel appropriate. Note that you can fit more than 400 floppy images on a single CD_ROM. (That'll save a lot of space!) As long as you can keep the images safe, you can dispose of the original floppies, and reconstruct them later if it ever turns out you need them.

writing images

Red Hat, Inc. has published a DOS utility you can use to write floppy disk images back to floppy disks. It's call rawrite.exe and is included on any Red Hat Linux CD-ROM. Since it is freely redistributable, I am happy to offer you a copy of the program and its documentation. It's really quite simple to use. Just run it and follow the prompts.

If you are running Linux, the command to restore an image to the floppy is:

dd if=floppy.img of=/dev/fd0 count=1 bs=1440k

where floppy.img is, of course, the name of your archived image file.

acknowledgements

Thanks to Alen Peacock for teaching me most of the knowledge embodied in this tutorial.

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