Re: [SLUG] filesystem identification

From: Eben King (eben1@tampabay.rr.com)
Date: Sat Oct 16 2004 - 14:18:04 EDT

On Sat, 16 Oct 2004, Chad Perrin wrote:

> Levi Bard wrote:
> > On Sat, 16 Oct 2004 11:12:14 -0400 (EDT), Eben King
> > <eben1@tampabay.rr.com> wrote:
> >
> >>OK, how does one identify the filesystem on a device? "file" says:
> >>
> >>[root@pc root]# file - < /dev/sda
> >>standard input: x86 boot sector
> >>
> >>(/dev/sda is one of these, 0.5 GB: http://kasercorp.com/usbjumbo.cfm )
> >>
> >>I successfully mounted it as ext2, but just because I happened to *know*
> >>that was what it was. In general, what should I do? How about an offset
> >>that'll skip ahead straight to the filesystem?
> >>
> >> offset in 1K blocks --vvv
> >>dd if=/dev/sda bs=1024 skip=xxx | file -
> >
> >
> > I never found a good solution to this other than trial && error.
>
> I don't recall, but . . . is it possible to mount a drive or partition
> without knowing the filesystem type, even if it's not in fstab?

Sure, but if it's some filesystem you haven't compiled yet, you're SOL.
Also, I have recent memories of "mount" mismounting a umsdos partition as
FAT, too. Looks like filesystem damage -- all the names, ownership,
permissions, some of the dates are trashed. Understandable, but still.

> In any case, some of the information spat out by running fsck on an
> unmounted filesystem might tell you what filesystem type it is. For
> instance, I ran fsck on a drive I thought was formatted ext3 and it
> informed me that fsck.reiserfs had been run on it, thus informing me
> that my guess at the filesystem type had been wrong. This also has the
> useful effect of telling you if the filesystem is damaged, in addition
> to telling you what type it is.

I've heard bad things about fsck.reiserfs, as in: if an ext[23]
fileystem gets damaged, you'll get most of your files back, but if you're
using reiserfs, hope your backup works. 

-- 
-eben    ebQenW1@EtaRmpTabYayU.rIr.OcoPm    home.tampabay.rr.com/hactar

                 Drive nail here > < for new monitor.

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