Re: [gentoo-user] flash drive FAT partition disappears

[Jesús Guerrero]

Hello, first, the disclaimer: take everything I'll say here as a starting
point, not as an universal truth. I am by no means specialist in this kind
of toys. 

On Thu, 19 Nov 2009 02:46:36 +0000, "Alan E. Davis" <lngndvs@×××××.com>
wrote:
> I can't think of a specific place to look for this, so will try the
> eclectics at gentoo-user.
>
> A student handed me a USB flash drive with a video file on it he wanted
to
> offer to me to watch.  It mounted automatically, I copied the file, then
I
> took the disk out of the drive and gave it to him.  I cannot say with
100%
> certainty that I unmounted it.  The file was completely copied.  I am
> pretty
> careful, so I think I unmounted it.

Even if you didn't, in my understanding, all that could cause (normally)
is a broken file system. The effects will usually depends on whatever was
happening at the moment, and at the fs you are using. Some mount options
can influence this as well. To palliate the effects of a catastrophic plug
off without having umounted before you can use the -osync mount option,
which will enable synchronous writes (making your device seems slower,
because writes will no longer be deferred/cached for a later oportunity).

But, that's not a substitute for a true umount, or a sync. It's just a way
to shorten the scope of any possible problem if you accidentelly unplug the
drive without having used umount first.

As a note, FAT is not precisely known for being too solid.

> Today he came back to me, asking what happened to his disk.  He said
> nothing
> it there anymore.  I checked.  Gparted says this drive (4 GB I think)
has 2
> Terabytes of unallocated space.  None of the Windoze gurus (so to speak)
> around here know what to do.
>
> Any ideas?   I'm afraid the little bit of progress I've made over the
past
> 13 years in advocating GNU/Linux and Free Softwrae, will be lost if this
> problem isn't solved.

Your problem with the size of the drive is a bit more alarming. It could
be a problem in your partition table. In that case, the chance is high that
testdisk can guess a valid partition table and restore the drive to a
working state. However, it could also be a fortuitous electric accident
that fried the unit, that happens sometimes, and it has nothing to do with
you or linux. In any case, and to max the chance to recover anything, the
first thing you should be doing is an image of the device, using dd, just
in case.

All this, assuming that the student didn't already mess up the drive.
Anyway, if s/he truly saved the only copy of anything important in a
pendrive and then sent it around the world, s/he almost deserves any pain
that could derive from that action.

-- 
Jesús Guerrero