Re: devfs again, (was RE: USB device allocation)

Horst von Brand (vonbrand@inf.utfsm.cl)
Fri, 08 Oct 1999 08:35:24 -0400


Shawn Leas <SLEAS@videoupdate.com> said:
> Horst von Brand [mailto:vonbrand@inf.utfsm.cl]

> >> through sudo to manage floppies.

> >"sudo mdir a:" is exactly as easy to use as "mdir a:". Dunno if something
> >like "sudo mcopy a:somepkg.tar.gz - | tar zxvf -" works, perhaps it does.

> >Also has the quite interesting side effect that "sudo mcopy /etc/shadow a:"
> >does work fine.

> I don't think we want to complain that devfs is at fault for the fact that
> sudo access can be dangerous.

What I want to say is that your "solution" creates more problems than there
were before. The Unix way (/dev is part of a real filesystem; permissions,
ownership, names, links, ... all work the same as with regular files) is a
time-tested design. Not flawless, but its flaws are known and workarounds
are in place. You propose to junk all that for a shiny, new way of doing
things that does break in many ways (see above). All for the tenuous
purpose of being able to address more devices (get a bigger dev_t, and be
done) or being able to fool around all day plugging/unplugging devices.

Note that just devfs does _not_ solve the "more devices" problem, as long
as major/minor stay limited. It can't really solve the "unplug sda, now sdy
is sdx" problem either (somehow devices _must_ be named, and this has to be
done somehow fixed, you can't just lug around the whole history of /dev),
and it can't solve the "unplug sdc, plug in another sdc, and then sdd; now
plug in the old sdc and have it be sdc again" problem. Any solution it
could offer for this is useless: I'd much prefer to be able to go and look
for /dev/disk-<some-serial-number> to check which <serial-number>s I've
used, and not having to remember that by my own because that particular
disk (out of the hundreds advocated by you) just so happens not to be on
line ATM. You want to unclutter /dev cluttering me.

BTW, the "devices get renamed" problem _is_ solved, and has been for quite
some time: You can mount by disk label or uuid, forget about the device name.

-- 
Dr. Horst H. von Brand                       mailto:vonbrand@inf.utfsm.cl
Departamento de Informatica                     Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria              +56 32 654239
Casilla 110-V, Valparaiso, Chile                Fax:  +56 32 797513

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