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On Linux (Debian based): If I copy files onto a floppy disk in an external floppy drive and put this disk later into another floppy drive, the disk output is … interesting. An excerpt:

scrambled output of healthy floppy disk's content

  • actual content is 5 files, the scrambled list contains way more (quit counting on "more than there should be")
  • the disk isn't recognized properly
  • filesystem's format is ext2, but the machine tries to mount as vfat
  • manually specifying the filesystem's type doesn't work
  • disk is okay, same results with different disks
  • problem arises only between these two guys (external, USB Floppy drive vs. internal Floppy drive): The both just tread "their" disks properly

Back on the "original" drive, everything works properly.

And yes, I've tried mounting it manually.

Question: Where would you start looking for answers for this curious behaviour on the affected machine?

dmesg output on this:

Error: Error informing the kernel about modifications to partition /dev/fd0p1 -- Invalid argument.  
This means Linux won't know about any changes you made to /dev/fd0p1 until you reboot -- 
so you shouldn't mount it or use it in any way before rebooting.
Error: Failed to add partition 1 (Invalid argument)

There's no /dev/fd0p1 on the machine too. There's the proper /dev/fd0.

Note on the Error message: I do get this error message on different Linux systems with different file systems at different occasions from time to time … up to now, I'm not aware of having run into any problems. I won't trust this peace, though

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    Could you give the commands you're using to format and mount your floppies? Having partitions on floppies is unusual to say the least! – Stephen Kitt Jul 15 '15 at 18:17
  • @StephenKitt The reason might be that I had to start partprobe to get any response after pushing the Floppy Disk in the machine. So: fdformat /dev/fd0 for formatting the floppy, and mke2fs -t ext2 -T floppy -m 1 for getting an ext2 Floppy, or `mkkosfs -F 12 -I" for a FAT12 Floppy. Funny thing is, that both systems are Debian Linux based (not Ubuntu!). – erch Jul 15 '15 at 20:05
  • How do you mount them? – Stephen Kitt Jul 15 '15 at 21:26
  • And how do you unmount them? – Gilles Jul 15 '15 at 23:24
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The key here is that if each drive can read its own disks, but not disks from the other drive, then one or both of them has misaligned heads. This is a very common problem with floppy drives, especially if they've been dropped.

Essentially it means that one drive is writing the data in the wrong spot, so other drives can't read it. As the same heads are used for reading and writing, the same drive can read those disks again perfectly well.

Try your disks in other drives if you can, as this will tell you which drive (if any) is correctly aligned. If disks written in any given drive don't work anywhere else at all, then you know that drive is misaligned.

Realigning a drive is a complicated affair requiring an oscilloscope and special analogue disks that aren't readily available, so replacing the drive is usually the easiest option.

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