[lug] FAT32 USB drive

[D. Stimits]

I see two possibilities. One is that the signal quality prevents some devices from reading this. This can happen more than people think, but it is still somewhat rare and not likely (if you have a long cable then this becomes more likely).

One thing many people do not realize is just how many options there are to various filesystem types. If you take a look at many of the modern distributions, specifically the file "/etc/mke2fs.conf", then you will find there are many optional parameters to the various variants of ext4. Older software may not handle all of the extensions, e.g., older 32-bit bootloaders will not recognize a valid ext4 filesystem if that filesystem has certain 64-bit extensions. In particular, older bootloaders on embedded systems tend to not find a filesystem at all if some of the 64-bit extensions are there, and this is true even though Linux itself can read this. The filesystem would be "missing" to anything not understanding those extensions.

I do not know what extensions or options might be possible with VFAT/FAT32, so I couldn't tell you what to check for. I would think that the systems creating the format could probably read their own partitions from that format, but you might find another system does not even see the content any better than if the filesystem were totally corrupt beyond any ability to repair.

On a system which cannot read the content you might try formatting again. Then copy the content back into the USB stick. My reason for saying to try this is that the system which cannot read a newer option will probably only create compatible formats. Older compatible formats can likely be read by the newer devices.

> On May 17, 2020 at 6:21 AM Davide Del Vento <davide.del.vento at gmail.com> wrote:
> 
>     Folks,
> 
>     I have a digital piano which can put stuff on USB devices (unspecified filesystem), so I formatted an USB drive to FAT32, put some stuff from the piano to it and tried to read them from my linux box.
> 
>     Funny enough, the drive showed empty in Linux, but the content was there when looking from the piano. I tried on a Mac which responded "The disk you inserted was not readable by this computer".
> 
>     So I tried Android. In fact I can see the digital piano files via Android (yay!)
> 
>     Funny thing, if I create files and directories on that USB drive from Linux, none of them shows up in Android.
> 
>     So it looks like this USB drive has two lives: one which is visible only from Linux, and the other which is visible from the digital piano and Android.
> 
>     Am I still sleeping and having a bad dream? Simple Googling did not reveal anything obvious....
> 
>     Thanks for any clues!
>     Davide
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