This exercise was a good training session and was sort of
a trip down Memory Lane. I am thankful that floppy disks are
mostly history but as long as the hardware is still there, it was
good to get useful tools that can on rare occasions, get one out
of a jam.
One of the things I learned while working with tomsrtbt
is that while it is possible to format 1.4 MB floppies to 1.7
megabytes, we must take care to make sure we know we are working
with one of the over-stuffed disks.
If you use the normal mount command such as
mount /media/floppy or some variation of that theme, the OS will
try to mount it as a 1.4 MB diskette and the mount will succeed
but nothing else will.
If you write to such a disk, you'll probably ruin it's
contents so if it is a valuable archive of some kind, you will
have trashed it.
If in doubt, slide the Write-Protect tab so that the hole
it covers is open. That way nothing can trigger a write.
You can add a device to /dev that makes the drive run on
21 sectors/82 tracks as in
#sudo mknod /dev/fd0u1722 b 2 60
#sudo mount /dev/fd0u1722 /media/floppy
When you mount it properly, it behaves like all the other
possible formats. If you mount a 1.72 disk the wrong way so the
system thinks it is 1.4 MB, an empty diskette will show lots of
dots .
$mount /media/floppy
mount: /media/floppy0: WARNING: device write-protected, mounted read-only.
$ls /media/floppy
÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷
÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷
÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷
÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷
÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷
÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷
÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷
÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷
÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷
÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷ ÷÷÷÷÷÷÷÷.÷÷÷
$umount /media/floppy
That was a 1.7 MB mounted wrongly as 1.4 MB. Here is the same
empty diskette mounted correctly.
$sudo mount /dev/fd0u1722 /media/floppy
mount: /media/floppy0: WARNING: device write-protected, mounted read-only.
$ls /media/floppy
$df -h /media/floppy
Filesystem Size Used Avail Use% Mounted on
/dev/fd0u1722 1.7M 0 1.7M 0% /media/floppy0
$exit
If the disk is empty, df -h will still show it as 1.7
which is okay but a populated 1.7 MB diskette will lie to you by
not showing it's capacity.
Here is a full disk mounted wrong.
$mount /media/floppy
mount: /media/floppy0: WARNING: device write-protected, mounted read-only.
$ls /media/floppy
boot.b bz2bzImage map rc.custom.gz settings.s
$df -h /media/floppy
Filesystem Size Used Avail Use% Mounted on
/dev/fd0 862K 836K 26K 97% /media/floppy0
$exit
There was nothing shown for capacity.
The rc.custom.gz file that was corrupt was really not
corrupt when mounted correctly and writing the modified zip file
back to the disk worked perfectly as long as the disk has no bad
sectors.
Let's see. If I was going to backup the hard drive on my
main Linux box, I'd need about 300-thousand of these storage
items so I thought I'd put it in a modern perspective.
The last floppy backup I did was around 2006 or so and I
don't miss not doing them at all, especially now with 512 GB hard
drives.
If you ever end up recovering any data with floppies,
write protect them especially if you are not sure how they were
made in the first place.
Martin McCormick
