What is filesystem panic?

James Wilkinson fedora at aprilcottage.co.uk
Tue Oct 28 21:36:52 UTC 2008


Per Anton Rønning wrote:
> I guess I should rephrase my question about my 4GB memory stick/pen,  
> where the filesystem
> now is set to readonly when I enter it into one of the slots.
> Could anyone tell me what might have happened by taking a look at the  
> snip of the logfile?
>
> I am not allowed to do anyting but reading files. I am not allowed to  
> delete files ,remove directires
> or write to files, even if I change to root privileges.
> I cannot say when this started - it just happened one time when I tried  
> to backup some files to the Jet Flash.
> Then I got the message (one example):
>  cp: cannot create regular file `/media/disk/trade/statQ': Read-only  
> file system
> Does anyone have a clue? I'd be grateful for pointers in the right  
> direction.
<snip>
> Oct 27 11:36:30 localhost kernel:    fat_free_clusters: deleting FAT  
> entry beyond EOF  [My remark: What does this
>                                                                           
>                                                  mean? Looks like an  
> error message]
> Oct 27 11:36:30 localhost kernel:    File system has been set read-only  
> [!!!!!!! - my remark]
> *** end snip ***

It looks to me like this is a logical inconsistency with the filesystem
on the drive.  Did you create it, or is it as the drive came?

A number of these drives come with slightly inconsistent partitioning
and formatting – it looks like this is becoming a FAQ. It’s possible
(but rather unlikely) that a stray Linux bug or memory errors corrupted
something. It’s slightly more likely that a bug in the drive itself
corrupted something.

In any of these cases, I’d recommend backing up everything that’s on the
disk, and either:
 * fdisk it to remove and recreate any partitions, then mkfs a new
   filesystem
 * just mkfs a filesystem on the “raw” device (e.g. /dev/sdc rather than
   /dev/sdc1).

Hints: the fdisk man page recommends cfdisk or parted to the traditional
fdisk program: you might want to try the graphical gparted. If you want
to use this disk under Windows, use
mkfs -t fat32 -F 32 -n diskname /dev/sdx
where diskname is the name you want to give the disk.

And make sure you do this on the right device! There is always the
prospect with these devices, if you’re not careful, of screwing up your
hard disk!

It’s vaguely possible that this disk’s reached its maximum number of
rewrites and has no spare sectors to swap in. If this is the case, then
it’s basically dead – it just allows you to get all the data off it.
(This seems to be the most normal failure mode with Flash, and is
definitely a Good Thing).

In any case, and as a general principle, never trust any disk too much.
If you haven’t got multiple copies of a piece of data (in multiple
locations), you haven’t really got it.

Hope this helps,

James.

-- 
E-mail:     james@ | Telsa ruthlessly depopulates the cuddly toy pile. There
aprilcottage.co.uk | is only room for so many penguins in any one house. Alan
                   | wakes. Telsa throws cuddly toys down the stairwell. Alan
                   | is struck by a blinding flash of penguin.
                   |     -- Telsa Gwynne’s Diary.




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