[wellylug] DD no go

[Brent Wood]

Um... Question... as I understood this stuff (which is not very well) the
reference below to sdb & sdb1 as disk devices seems strange. I thought sdb was
a the instantiation of the physical device on the filesystem & sdb1,2,3 etc are
partitions on this? 

So is this a typo or am I more ignorant than thought about this?

Brent



--- Cliff Pratt <enkidu at cliffp.com> wrote:

> David Antliff wrote:
> > On Sat, Apr 5, 2008 at 11:37 AM, Cliff Pratt <enkidu at cliffp.com> wrote:
> >>  > Thirdly, there's nothing special that comes to mind about the number
> >>  > 4298739712, in case you were wondering.
> >>  >
> >>  It's pretty close to 4GB which is a FAT32 filesystem limit. Or is it?
> >>  I'm fairly sure there are a number of limits, 2GB being one of them.
> > 
> > But... but... /dev/sdb is a disk device... he's not writing to a file
> > *ON* a FAT32 filesystem, he's writing to a block device that just
> > happens to contain a (new) FAT32 filesystem, and he's nuking it by
> > writing there...
> >
> True.
>  >
> > As far as dd is concerned, whatever is on sdb is irrelevant. It's just
> > going to overwrite it. The same would apply if he was writing to
> > partition sdb1 containing a FAT32 filesystem - it will simply
> > overwrite it. Where this *would* apply is if he had created a FAT32
> > filesystem on partition /dev/sdb1 and mounted it at, say, /mnt/blah
> > and he was trying to dd of=/mnt/blah/myfile.
> > 
> > /dev/sdb and /dev/sdb1 (and all other 'disk' devices) are just block
> > devices - filesystems make no sense here, they are data structures
> > stored ON a block device.
> > 
> > It's very unusual to create a filesystem on a disk device. It's far
> > more common to partition the disk device into multiple partitions and
> > then create a filesystem on one of those. I'm not even sure what
> > happens if you try and create a filesystem on a disk device and mount
> > it. Should work I suppose? Unusual though.
> > 
> As regards filesystems on devices, don't floppy disks work that way? And 
> CDs/DVDs and USB keys? (I could be wrong!)
> 
> Cheers,
> 
> Cliff
> 
> 
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