28 Dec
2011
28 Dec
'11
7:34 a.m.
On Mon, 12/26/11, Warren Toomey <wkt(a)tuhs.org> wrote:
> A question though: what command would
"bring the system down"?
On Wed, Dec 28, 2011 at 01:13:54AM +0100, Sven Mascheck wrote:
I wonder if Warren rather had different issues in
mind,
I just took umbrage at the article, in that it implied Unix provided
machanisms for the ordinary user to "bring the system down". This is,
of course, not true, at least once the hardware supported
inter-process and kernel protection.
However, it does remind me of Dennis' story about the days before proper
memory protection (from http://cm.bell-labs.com/cm/cs/who/dmr/odd.html)
Back around 1970-71, Unix on the PDP-11/20 ran on hardware that
not only did not support virtual memory, but didn't support
any kind of hardware memory mapping or protection, for example
against writing over the kernel. This was a pain, because we were
using the machine for multiple users. When anyone was working on
a program, it was considered a courtesy to yell "A.OUT?" before
trying it, to warn others to save whatever they were editing.
At some point several were sitting around working away. Bob
Morris asked, almost conversationally, "what are the arguments to
ld?" Someone told him. We continued typing for the next minute,
as a thought began to percolate, not quite to the top of the
brain -- in other words, not quite fast enough. The terminal
stopped echoing before anyone could stop and say "Hold on Bob,
what is it you're trying to do?"
Cheers,
Warren