[TUHS] hello, world

[TUHS] hello, world

[Norman Wilson]

Rather a nice tribute to Dennis and C, published
in the New York Times Magazine:

http://www.nytimes.com/interactive/2011/12/22/magazine/the-lives-they-lived.html?ref=magazine#view=dennis_ritchie

[TUHS] hello, world

[Warren Toomey]

On Sun, Dec 25, 2011 at 08:10:04AM -0500, Norman Wilson wrote:
> Rather a nice tribute to Dennis and C, published
> in the New York Times Magazine:
> 
> http://www.nytimes.com/interactive/2011/12/22/magazine/the-lives-they-lived.html?ref=magazine#view=dennis_ritchie

Yes, a good reminder on the power that programming brings us. A question
though: what command would "bring the system down"?

Thanks Norman,
	Warren

[TUHS] hello, world

[Wilko Bulte]

Quoting Warren Toomey, who wrote on Tue, Dec 27, 2011 at 07:11:45AM +1000 ..
> On Sun, Dec 25, 2011 at 08:10:04AM -0500, Norman Wilson wrote:
> > Rather a nice tribute to Dennis and C, published
> > in the New York Times Magazine:
> > 
> > http://www.nytimes.com/interactive/2011/12/22/magazine/the-lives-they-lived.html?ref=magazine#view=dennis_ritchie
> 
> Yes, a good reminder on the power that programming brings us. A question
> though: what command would "bring the system down"?

kill -9 1 

?

> Thanks Norman,
> 	Warren
> _______________________________________________
> TUHS mailing list
> TUHS at minnie.tuhs.org
> https://minnie.tuhs.org/mailman/listinfo/tuhs
--- End of quoted text ---

[TUHS] hello, world

[Lyndon Nerenberg]

On 2011-12-26, at 13:11 PM, Warren Toomey wrote:

> Yes, a good reminder on the power that programming brings us. A question
> though: what command would "bring the system down"?

'kill -1 1' will bring terror to anyone who had the misfortune of dealing with Xenix.

I think the writer is getting at how UNIX bypassed the 'i ask you three times' dance.

--lyndon

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[TUHS] hello, world

[Armando Stettner]

I, of course, liked the warning from dump(1): "Are you sure you know what you are doing?"

  aps.


Begin forwarded message:

> From: Lyndon Nerenberg <lyndon at orthanc.ca>
> Subject: Re: [TUHS] hello, world
> Date: December 26, 2011 4:20:38 PM EST
> To: Warren Toomey <wkt at tuhs.org>
> Cc: tuhs at tuhs.org, Norman Wilson <norman at oclsc.org>
> 
> 
> On 2011-12-26, at 13:11 PM, Warren Toomey wrote:
> 
>> Yes, a good reminder on the power that programming brings us. A question
>> though: what command would "bring the system down"?
> 
> 'kill -1 1' will bring terror to anyone who had the misfortune of dealing with Xenix.
> 
> I think the writer is getting at how UNIX bypassed the 'i ask you three times' dance.
> 
> --lyndon
> 
> _______________________________________________
> TUHS mailing list
> TUHS at minnie.tuhs.org
> https://minnie.tuhs.org/mailman/listinfo/tuhs

[TUHS] hello, world

[Michael Davidson]

--- On Mon, 12/26/11, Armando Stettner <aps at ieee.org> wrote:

I, of course, liked the warning from dump(1): "Are you sure you know what you are doing?"

... or the even scarier "Last chance before scribbling on hp(0,0)" from restor ...

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[TUHS] hello, world

[A. P. Garcia]

On Mon, Dec 26, 2011 at 3:11 PM, Warren Toomey <wkt at tuhs.org> wrote:

> On Sun, Dec 25, 2011 at 08:10:04AM -0500, Norman Wilson wrote:
> > Rather a nice tribute to Dennis and C, published
> > in the New York Times Magazine:
> >
> >
> http://www.nytimes.com/interactive/2011/12/22/magazine/the-lives-they-lived.html?ref=magazine#view=dennis_ritchie
>
> > Yes, a good reminder on the power that programming brings us. A question
> > though: what command would "bring the system down"?
>

anything that consumes too many resources, i suppose. the morris worm would
have several copies of itself running on the same machine running a
password cracker, using up all the cpu and bringing the system to its
knees. hog too much memory and you could run into thrashing. even more evil
things may include a fork bomb, perhaps? or emacs? ;-)
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[TUHS] hello, world

[A. P. Garcia]

When I worked at a university, one of our linux web servers crashed one
day. In place of /dev/null was a history file. The last entry?

mv .bash_history /dev/null

Ah, script kiddies...
On Dec 26, 2011 3:28 PM, "A. P. Garcia" <a.phillip.garcia at gmail.com> wrote:

> On Mon, Dec 26, 2011 at 3:11 PM, Warren Toomey <wkt at tuhs.org> wrote:
>
>> On Sun, Dec 25, 2011 at 08:10:04AM -0500, Norman Wilson wrote:
>> > Rather a nice tribute to Dennis and C, published
>> > in the New York Times Magazine:
>> >
>> >
>> http://www.nytimes.com/interactive/2011/12/22/magazine/the-lives-they-lived.html?ref=magazine#view=dennis_ritchie
>>
>> > Yes, a good reminder on the power that programming brings us. A question
>> > though: what command would "bring the system down"?
>>
>
> anything that consumes too many resources, i suppose. the morris worm
> would have several copies of itself running on the same machine running a
> password cracker, using up all the cpu and bringing the system to its
> knees. hog too much memory and you could run into thrashing. even more evil
> things may include a fork bomb, perhaps? or emacs? ;-)
>
>
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[TUHS] hello, world

[Michael Davidson]

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--- On Mon, 12/26/11, Warren Toomey <wkt at tuhs.org> wrote:
 A question though: what command would "bring the system down"?

Well, if you are logged in as root the possibilities are almost endless, the classic one being:

# rm -rf *

run from the root directory. Strictly speaking, of course, that doesn't "bring the system down" but there really isn't much that you can do with the system after running it ...


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[TUHS] hello, world

[Sven Mascheck]

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Michael Davidson wrote:
> --- On Mon, 12/26/11, Warren Toomey <wkt at tuhs.org> wrote:
>  A question though: what command would "bring the system down"?
> 
> Well, if you are logged in as root the possibilities are almost endless, [...]

Sure.  I was just tempted to exaggerate this discussion with:
"init 0, halt or shutdown".  But such commands had no been
implemented even in 7th ed, yet :)

I wonder if Warren rather had different issues in mind,
which would lead to "unexpected" downs. The previously
mentioned resource problems probably match this--not too
suprisingly, because I always had the impression that Unix
aimed at protecting processes from each other, not users.

I'd like to remind of an according, earlier, quite fitting
discussion from DMR:

In "The UNIX Time-sharing System--A Retrospective"
the paragraph "Security"
http://cm.bell-labs.com/cm/cs/who/dmr/retro.html

-Sven

[TUHS] hello, world

[Wilko Bulte]

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Quoting Sven Mascheck, who wrote on Wed, Dec 28, 2011 at 01:13:54AM +0100 ..
> Michael Davidson wrote:
> > --- On Mon, 12/26/11, Warren Toomey <wkt at tuhs.org> wrote:
> >  A question though: what command would "bring the system down"?
> > 
> > Well, if you are logged in as root the possibilities are almost endless, [...]
> 
> Sure.  I was just tempted to exaggerate this discussion with:
> "init 0, halt or shutdown".  But such commands had no been
> implemented even in 7th ed, yet :)

ISTR that starting another init has it's own interesting effects though :)

Wilko

> 
> I wonder if Warren rather had different issues in mind,
> which would lead to "unexpected" downs. The previously
> mentioned resource problems probably match this--not too
> suprisingly, because I always had the impression that Unix
> aimed at protecting processes from each other, not users.
> 
> I'd like to remind of an according, earlier, quite fitting
> discussion from DMR:
> 
> In "The UNIX Time-sharing System--A Retrospective"
> the paragraph "Security"
> http://cm.bell-labs.com/cm/cs/who/dmr/retro.html
> 
> -Sven
> _______________________________________________
> TUHS mailing list
> TUHS at minnie.tuhs.org
> https://minnie.tuhs.org/mailman/listinfo/tuhs
> 
--- End of quoted text ---

[TUHS] hello, world

[Warren Toomey]

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 On Mon, 12/26/11, Warren Toomey <wkt at 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

[TUHS] hello, world

[Ori Idan]

On Mon, Dec 26, 2011 at 11:28 PM, Michael Davidson <m_d at pacbell.net> wrote:

> --- On *Mon, 12/26/11, Warren Toomey <wkt at tuhs.org>* wrote:
>
>  A question though: what command would "bring the system down"?
>
> Well, if you are logged in as root the possibilities are almost endless,
> the classic one being:
>
> # rm -rf *
>
> run from the root directory. Strictly speaking, of course, that doesn't
> "bring the system down" but there really isn't much that you can do with
> the system after running it ...
>
>
>
> That's reminds me of an accident happened to a friend who try making some
order on his computer and since he did not know exactly what a file named
unix is doing, he deleted it. The system worked but of course would not
boot again...

-- 
Ori Idan
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[TUHS] hello, world

[Adam]

> Yes, a good reminder on the power that programming brings us. A question
> though: what command would "bring the system down"?

Great read.
Would just like to add that on some Unixes a simple command with no
args will bring a system down - killall.

Adam

[TUHS] hello, world

[Cyrille Lefevre]

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Le 27/12/2011 07:11, Adam a écrit :
>> Yes, a good reminder on the power that programming brings us. A question
>> though: what command would "bring the system down"?
>
> Great read.
> Would just like to add that on some Unixes a simple command with no
> args will bring a system down - killall.

happy new year to everyone.

that rememer the day where I was looking on IRIX killall manual in a
window which say you could "killall some_process_by_name" and try it
on a... solaris server in another window. the answer was fast :
well, humm, where is my second window ?

PS : solaris killall doesn't take args %-/

Regards,

Cyrille Lefevre
-- 
mailto:Cyrille.Lefevre-lists at laposte.net

[TUHS] hello, world

[Tim Newsham]

On Mon, Dec 26, 2011 at 8:15 PM, Dave Horsfall <dave at horsfall.org> wrote:
> On Tue, 27 Dec 2011, Warren Toomey wrote:
>> Yes, a good reminder on the power that programming brings us. A question
>> though: what command would "bring the system down"?
>
> It's right here: "Programmers were free to poke around to see and directly
> manipulate what was in the computer's memory."

http://minnie.tuhs.org/pipermail/unix-jun72/2008-May/000250.html

> -- Dave

-- 
Tim Newsham | www.thenewsh.com/~newsham | thenewsh.blogspot.com

[TUHS] hello, world

[Corey Lindsly]

> On Sun, Dec 25, 2011 at 08:10:04AM -0500, Norman Wilson wrote:
> > Rather a nice tribute to Dennis and C, published
> > in the New York Times Magazine:
> > 
> > http://www.nytimes.com/interactive/2011/12/22/magazine/the-lives-they-lived.html?ref=magazine#view=dennis_ritchie
> 
> Yes, a good reminder on the power that programming brings us. A question
> though: what command would "bring the system down"?

The one that has stuck with me since the first time I read it 30 years ago
is from an article titled "On the Security of UNIX" (dmr, 1978?) ... 

  Here is a particularly ghastly shell sequence guaranteed
  to stop the system:
    
    while :; do
      mkdir x
      cd x
    done

  Either a panic will occur because all the i-nodes on the
  device are used up, or all the disk blocks will be consumed,
  thus preventing anyone from writing files on the device.

(from the UNIX programmer's manual, vol.2 p.592)

---corey

[TUHS] hello, world

[asbesto]

Tue, Dec 27, 2011 at 04:53:44PM -0800, Corey Lindsly wrote:

> > Yes, a good reminder on the power that programming brings us. A question
> > though: what command would "bring the system down"?
> 

So I have to cite here our shell UNIX Forkbomb, coded by
Jaromil, that will bring on knees almost every misconfigured system:

 :(){ :|:& };:

some references here:

 http://www.runme.org/project/+forkbombsh/
 http://en.wikipedia.org/wiki/Jaromil

I think some limits/ulimits configuration can prevent this but
i'm not so sure about it ;)


-- 
[ ::::::::: 73 de IW9HGS : http://freaknet.org/asbesto ::::::::::: ]
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[TUHS] hello, world

[John Cowan]

asbesto scripsit:

> So I have to cite here our shell UNIX Forkbomb, coded by
> Jaromil, that will bring on knees almost every misconfigured system:
> 
>  :(){ :|:& };:

Well, that version depends on shell functions, a relatively modern
(in TUHS terms) feature of the shell.  A more classical fork bomb,
which will run on every shell, is to place the following into a file:

	$0 & $0 &

and execute the file.

-- 
John Cowan   cowan at ccil.org    http://ccil.org/~cowan
If a soldier is asked why he kills people who have done him no harm, or a
terrorist why he kills innocent people with his bombs, they can always
reply that war has been declared, and there are no innocent people in an
enemy country in wartime.  The answer is psychotic, but it is the answer
that humanity has given to every act of aggression in history.  --Northrop Frye

[TUHS] hello, world

[David Barto]

A long time ago at the University that I graduated from. . .

Shell scripts had just added the ability to have functions in them, so I wrote a script to do some processing of files that I had, and then logged off to let it run in the background.

The shell script was named 'A'.

In the script was a function, named 'A'

When the script ran, instead of calling 'A' the function, it called 'A' the script, and you can see where this goes from here.

2 days later I received an email from the admin (thankfully a friend) who enclosed the 'ps -axl' output from the machine. It showed thousands of copies of my script running and a load that indicated that the machine was useless for almost everything.

With the admonishment: "Don't ever do this again."

I haven't.

	David


David Barto
barto at kdbarto.org
barto at ucsd.edu