USB flash drive changes to read-only on the fly

[Vaibhav Dalvi]

On Thu, Sep 23, 2010 at 3:21 AM, andrew clarke <mail at ozzmosis.com> wrote:

> On Wed 2010-09-22 22:21:27 UTC+0200, Daniel Louw (daniel at dline.co.za)
> wrote:
>
> > This might be a silly question, but it is very frustrating.
> >
> > I have this memory stick, a 2 GB one formatted with FAT32.
> >
> > I was working on a .C file stored on the memory stick, saving as I
> > made progress with the code. Then all of a sudden I cannot save
> > anymore. I get an error saying the disk is read only. I cannot create
> > new folders or files or anything. chmod doesn't work, it simply says
> > read only partition. What the hell?
> >
> > Could it be because I compile directly on the disk? I use the disk a
> > lot at university and it is much easier to just work directly on the
> > disk.
>
> Not a silly question.
>
> Compiling directly on the memory stick is no different to writing any
> other type of file to the disk.  As far as Linux is concerned it's
> just another drive.
>
> I suspect there is some sort of FAT32 filesystem corruption on the
> memory stick, and once the Linux kernel encounters it it switches its
> FAT32 driver to read-only as to not cause any further corruption. You
> can do a file system check/repair on the memory stick from the Ubuntu
> GUI - System -> Administration -> Disk Utility.  Then select the
> memory stick's FAT32 partition and click Check Filesystem.  You may
> need to click on Unmount Volume first.
>
> On the other hand you may have encountered a bug in the FAT32
> driver, although given the number of years people have been using
> FAT32 in Linux this is pretty unlikely.  :-)
>
> /var/log/messages may give you some clues.  You can view it from the
> Ubuntu GUI - under System -> Administration -> Log file viewer.
>
> FAT32 is pretty fragile.  Instead of doing the FAT32 filesystem check
> above you may just want to make a backup of your data on the memory
> stick, reformat it as NTFS and copy the data back.  NTFS is a bit more
> robust, with errors in the filesystem generally handled a lot more
> gracefully.
>
> There are few reasons not to use NTFS on memory sticks these days. For
> example the NTFS driver in Apple Mac OS X is read-only but you can
> download/install software to allow read/write NTFS drives on OS X.
> Similarly FreeBSD and other lesser-known operating systems.
>
> Regards
> Andrew
>
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More chances are that your fat32 FS got an error. Which means you don't have
any other option than to copy the data else where and format it. It might be
the reason that your pen drive's flash chip is failing. I had a Transcend
512MB USB Drive and just couple of months ago it failed permanently. I was
getting similar ReadOnly FS situations for a month ago. I used to reformat
it and use it again. But after a while it stopped replying to the PC. No
reply - no device initiation - and I have a dead USB Drive. Not sorry though
that thing cost me
Rs 650/- five yrs ago. i.e roughly $13 and had 3yrs warranty.

Regards,
Vaibhav Dalvi
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