Accessing partitions in drive images

[Joshua Judson Rosen]

Ben Scott <dragonhawk at gmail.com> writes:
>
> On Sun, Jan 29, 2012 at 12:45 PM, Joshua Judson Rosen
> <rozzin at geekspace.com> wrote:
> > I've always wondered: why do the little USB flash sticks,
> > SD cards, etc. all include a partition-table with one
> > partition? Why don't they just use whole-device filesystems?
> 
>   Because they're not floppy disks, and fixed disks are assumed to
> have a partition table.

I'm sure it's just me not understanding (which is why I asked
the question in the first place), but this sounds like
`begging the question' to me; I think the part that I don't get
is really...:

> Flash drives wouldn't work as floppies, so they're treated as fixed
> disks.

What does this mean? Why wouldn't USB sticks or MMC/SD cards work
`as floppies'?

At least from my view as a casual observer/user, they seem to be
a lot more similar to floppies than `fixed disks'.

Also..., what does the "fixed" in "fixed disk" mean?

I'm probably `letting myself be dumb' on this topic more than I should
(which is still something short of `playing devil's advocate'); I do
have a vague recollection of the SD/MMC architecture as... something that
plugs directly into the host bus and contains its own IDE controller?

And I know that USB drives identify themselves as `general mass storage'
devices (generally...), but they could well identify themselves as
anything; I know that I have a couple of U3 USB flash-sticks that
identify themselves as *multiple* devices, one of which is a `CD-ROM'
device, for example. And there *are* USB floppy-drives, aren't there?
Now I wonder what device-class those are in; grep'ing the web finds
a draft revision of the USB spec. that actually said:

    General Mass Storage subclass. Mass Storage devices are normally
    used in a random access fashion. The General Mass Storage subclass
    includes storage devices such as the following:

        * Conventional floppy
        * Magneto-optical
        * Zip (floptical)
        * Syquest
        * Hard drives


It looks like the final version of that document ended up very different,
but it still leaves me with the question of... what `wouldn't work'
about USB flash-sticks presenting more like floppies than HDDs?
It seems like a `floppy-like presentation' would be much more inline
with the Principle of Least Astonishment....

>   There's nothing insurmountable that keeps one from just putting a
> filesystem on a USB flash drive.  Indeed, you can do it, and Linux
> software will generally be just fine.  But it breaks a lot of
> assumptions that could screw up BIOSes and other OSes, and/or lead to
> those same things trying to write a partition table into your
> filesystem.  And since your flash drive is technically laid out in a
> non-standard manner (again, I use the term "standard" loosely), it
> would arguably not be their fault.

The thing that's actually piqued my interest is that I recently received
a whole-device (partitionless) FAT-formatted USB flash-stick... from
a Mac user.

>   Next up: Why are console windows traditionally 80 columns wide?

Because 80 is an optimal mix of `nice round radix-2 number' and
`nice round radix-10' number? ☺

(like how `1.44-MB floppies' were actually 1474560 bytes?)

-- 
"Don't be afraid to ask (λf.((λx.xx) (λr.f(rr))))."