Crashing Unix
Nick
of it.
I am being taught Unix at University and during one lecture, the lecturer
kept going on about us crashing it and he seemed disappointed that no-one
managed it.
Is there any kind of script or combination of commands that will crash Unix
on a network? We cannot access the internet from our Unix server and using
ftp between Windows & Unix is the only method of file transfer.
I don't want to permanently screw up the system, just make it crash to see
how it can be done.
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Nick
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buzzbomb
years I have been working with it the only time I have had Unix (and I mean
the OS not the many services can run) crash on me is with dodgy hardware, or
with early versions of Solaris 2 which would crash if you sneezed too loud.
Unix is generally very, very robust as witnessed by its use in thousands of
mission critical apps all over the world. I wonder which planet/era you
lecturer is from (possibly Planet Microsoft) ?
B.
"Nick" <goonerblo...@hotmail.com> wrote in message
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Nick
thinking he is from planet MS.
I wonder if you can tell me how Linux compares with Unix? One of my friends
insists its very similar and that commands are pretty much the same, I've
never used it so I cannot comment.
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Nick
"buzzbomb" <buzz...@cut-this.ntlworld.cut-this.com> wrote in message
news:Rlok8.4595$w65.4...@news6-win.server.ntlworld.com...
dave...@spamcop.net
> I am a newcomer to Unix and only have very limited knowledge and experience
> of it.
> I am being taught Unix at University and during one lecture, the lecturer
> kept going on about us crashing it and he seemed disappointed that no-one
> managed it.
Well, it's not a particularly easy thing to do, unless he has made the
system intentionally vulnerable as a challenge.
> Is there any kind of script or combination of commands that will crash Unix
> on a network?
Maybe.
> We cannot access the internet from our Unix server and using
> ftp between Windows & Unix is the only method of file transfer.
Pretty limiting.
> I don't want to permanently screw up the system, just make it crash to see
> how it can be done.
Don't like going to school where you do, and are looking to change schools
are you? This is a perfect way to get kicked out (and maybe not be able to
get into another good school). Not sure why you'd want to do that.
It's also pretty unlikely that a bunch of Unix professionals would
go out of their way to share security vulnerabilities in this situation,
by the way. We spend our time trying to *stop* that sort of thing
(very successfully in most cases), so it would be unwise to give you any
information which would possibly threaten the security of your systems,
and would certainly threaten your standing at your school.
Dave Hinz
Nick
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Nick
<dave...@spamcop.net> wrote in message
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dave...@spamcop.net
> thinking he is from planet MS.
> I wonder if you can tell me how Linux compares with Unix? One of my friends
> insists its very similar and that commands are pretty much the same, I've
> never used it so I cannot comment.
Any intelligent person can learn how to properly admin a Linux box, and
apply the knowledge directly to being a Unix sysadmin. Learn what the tools
*do*, not just how to use them, and you'll do fine. Make sure you get
a recent distribution of Linux, as it's improving tremendously with each
release.
Linux is no more different from Unix, than various flavors of unix are
different from each other. After a while, you can move from one to another
without a second thought.
Dave Hinz
buzzbomb
Unix guy...
Unix used to refer to a family of OS's that were built on AT&T code which
was initially developed in the early 70's (initial development can be traced
back to '69). There were variants & branches from the original, most notably
BSD.
In the 80's there we move to standardise the various "Unices", using common
API's, allowing applications to run on all the different flavours with
little or no modification. This resulted in a number of standards under the
POSIX banner.
Linux is an OS scratch written to meet the POSIX standards - so its not Unix
in the original sense. However its virtually indistinguishable as it is
POSIX compliant and uses many of the same tools/commands etc.
B.
"Nick" <goonerblo...@hotmail.com> wrote in message
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Alun Jones
>Linux is an OS scratch written to meet the POSIX standards - so its not Unix
>in the original sense. However its virtually indistinguishable as it is
>POSIX compliant and uses many of the same tools/commands etc.
By that logic, you could call Windows NT "Unix" :-)
Alun.
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buzzbomb
However, from what I know of NT its conforms to only a small subset of the
POSIX standard set. Just enough to get a tick in the box from those RFP's
that require POSIX compliance (mainly government).
But I think you've got my logic crossed %~).
My argument was that Linux is not a true Unix (in the original sense) as its
not based on AT&T core code. However its sufficiently similar, not just
because of POSIX compliance, to, IMO be made an honourary Unix ;)
B.
"Alun Jones" <al...@texis.com> wrote in message
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Nick Maclaren
In article <WJok8.4738$w65.4...@news6-win.server.ntlworld.com>,
"buzzbomb" <buzz...@cut-this.ntlworld.cut-this.com> writes:
|> I'm not sure what it says about your University if this lecturer is the top
|> Unix guy...
Hell, if I was giving a course on Unix administration and I set
a task of crashing it, I would be VERY disappointed if nobody
could manage it. Crashing almost any general-purpose system
on purpose is a doddle - it wasn't hard to crash even MVS before
MVS/XA. No, I am not going to post how.
Now, crashing a system WITHOUT leaving a trace of who was responsible
can be much more of a challenge, depending a lot on how the system
has been designed and configured.
|> In the 80's there we move to standardise the various "Unices", using common
|> API's, allowing applications to run on all the different flavours with
|> little or no modification. This resulted in a number of standards under the
|> POSIX banner.
There were many such attempts, over a couple of decades, and it
wasn't (and isn't) actually POSIX's intention to standardise the
Unices, so much as to allow the development of genuinely portable
code.
Recently, there have been attempts to standardise some of the
"standards", which have led to POSIX 2001, for what it is worth.
|> Linux is an OS scratch written to meet the POSIX standards - so its not Unix
|> in the original sense. However its virtually indistinguishable as it is
|> POSIX compliant and uses many of the same tools/commands etc.
It is not clear whether Unix in the original sense still exists.
Few, if any, Unices are based on A,T&T's original code any longer,
not even A,T&T's SVR4, though there are traces of the original left
in some of the documentation, interfaces, headers and occasionally
code. I doubt that even Solaris (one of the few commercial Unices
based on SVR4) has much of A,T&T's code left.
And, as Alun Jones says, there is a lot more to Unix than POSIX
compatibility and the availability of most of the standard commands.
Linux is a Unix, as much as AIX, IRIX, HP-UX, Solaris and so on are.
Regards,
Nick Maclaren,
University of Cambridge Computing Service,
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England.
Email: nm...@cam.ac.uk
Tel.: +44 1223 334761 Fax: +44 1223 334679
Harri J Haataja
>They do say imitation is the sincerest form of flattery ;)
>
>However, from what I know of NT its conforms to only a small subset of the
>POSIX standard set. Just enough to get a tick in the box from those RFP's
>that require POSIX compliance (mainly government).
"Those who do not understand Unix are condemned to reinvent it,
poorly." -- Henry Spencer
"Those who try to (re)implement windows(tm) are missing the point of
unix."
-- A. P. Garcia
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p...@icke-reklam.ipsec.nu
> I am a newcomer to Unix and only have very limited knowledge and experience
> of it.
> I am being taught Unix at University and during one lecture, the lecturer
> kept going on about us crashing it and he seemed disappointed that no-one
> managed it.
> Is there any kind of script or combination of commands that will crash Unix
> on a network? We cannot access the internet from our Unix server and using
> ftp between Windows & Unix is the only method of file transfer.
> I don't want to permanently screw up the system, just make it crash to see
> how it can be done.
Well, just pull the power cord :-) Works most of the times. And it's portable
too, works on wintendo and MAC also.
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> Nick
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Sorry about my e-mail address, but i'm trying to keep spam out.
Remove "icke-reklam" and it works.
Alun Howells
trivial script which creates a large file in /tmp and hen runs two copies of
itself again in the background. Very soon you will either fill up all of
/tmp which will stop alot of applications from running or youll reach a
limit of the number of processes in the version of the OS. If the sysadmin
was good he'll have limited the number of processes your account can run,
but this it not usualy the case. You might want to fill up /var/tmp too.
a file called 'crashme.sh' somthing like...
#!/bin/sh
crashme.sh &
crashme.sh &
man man > /tmp/afilename`date` &
man man > /var/tmp/afilename`date` &
Oh , and youll probably get expelled.
- Alun
"Nick" <goonerblo...@hotmail.com> wrote in message
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Nick Upson
machine I was using at the time with a powerfail.
It turned out to be a write to an un-initialised pointer was
causing it.
It was a sequent machine I think but it was several years ago.
Nick
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Luke Vogel
>
> I'm just trying to increase my understanding of it
Do you have root? If so,
rm -fr /
should just about do it. :)
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Douglas Siebert
>I am a newcomer to Unix and only have very limited knowledge and experience
>of it.
>I am being taught Unix at University and during one lecture, the lecturer
>kept going on about us crashing it and he seemed disappointed that no-one
>managed it.
>Is there any kind of script or combination of commands that will crash Unix
>on a network? We cannot access the internet from our Unix server and using
>ftp between Windows & Unix is the only method of file transfer.
>I don't want to permanently screw up the system, just make it crash to see
>how it can be done.
Well, on recent versions of Linux:
echo 1 > /proc/sys/kernel/panic
This isn't really "crashing" as such since this is a way to deliberate
cause it to crash for testing purposes, but the net effect is the same.
Just about any Unix will crash if you write random data in /dev/kmem.
You must be root for either of these methods to work.
The trick is to find ways to crash it as a normal user. More difficult,
but doable (can't point to anything offhand though) There used to be
a program called 'crashme' floating around the net that executed random
syscalls and random code and was able to crash pretty much any Unix
system, given enough time. I think it was used as a way to detect bad
conditions and improve the robustness of the kernel, so it may no longer
work, at least on some systems. Haven't tried it in about 10 years.
There was a bug a few years back called the "ping of death" that was
able to crash a large variety of systems (many Unixes, Windows, even
some network devices like routers, switches, etc.) that was particularly
bad since someone could crash a system on the other side of the world
and all they needed was to be able to send a 'ping' packet to it. That
bug was quickly fixed after it became known, needless to say :)
--
Douglas Siebert dsie...@excisethis.khamsin.net
A good friend will help you move, a true friend will help you move a body.
Bernd Eckenfels
> Well, on recent versions of Linux:
> echo 1 > /proc/sys/kernel/panic
> This isn't really "crashing" as such since this is a way to deliberate
> cause it to crash for testing purposes,
Have you tried it?
/usr/src/linux/Documentation/sysctl/kernel.txt
panic:
The value in this file represents the number of seconds the
kernel waits before rebooting on a panic. When you use the
software watchdog, the recommended setting is 60.
This is the same Option as NT ofers to automatically reboot after a kernel
panic. Nothing to do with crashing/testing.
Greetings
Bernd
Bernd Eckenfels
> You sound like a would be cracker. No, no one legit is going to tell
> you, because you'd actually try it! Get your own machine and crash
> that, don't go crashing machines that people are trying to use.
Using crashme would be the first step. Doing that actually is a nice service
you can do t the community (if you report errors :)
Greetings
Bernd
dave...@spamcop.net
And it's a great way to get kicked out of college, and possibly prosecuted.
Learning the system is one thing, but responding to some prof's vague,
most likely unauthorized challenge, is supremely unwise.
those who know me have no need of my name
>And, as Alun Jones says, there is a lot more to Unix than POSIX
>compatibility and the availability of most of the standard commands.
>Linux is a Unix, as much as AIX, IRIX, HP-UX, Solaris and so on are.
only two of those you've named are unix branded.
but you are right in that they are all similar enough. but is that
a feature of posix or unix, or some of both, or other things (too)?
--
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those who know me have no need of my name
>In alt.unix.wizards Nick <goonerblo...@hotmail.com> wrote:
>> I don't want to permanently screw up the system, just make it crash to see
>> how it can be done.
>
>Don't like going to school where you do, and are looking to change schools
>are you? This is a perfect way to get kicked out (and maybe not be able to
>get into another good school). Not sure why you'd want to do that.
this is perhaps sage advice, though the instructor (supposedly) did
invite the attempts.
Thomas K
on the spot.. now it could be a homework assignment to come back with
possible ways to crash the system. In any case, I doubt he'd get busted for
it if the prof really did invite them to do it since its probably not a
mission critical box, like email, accounting, scheduling, etc.
--
Thomas the out of work NOC technician
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Remove the WAZUP & FOO from my email addy.
<dave...@spamcop.net> wrote in message
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Will Packard
>
> Nick wrote:
> >
> > I'm just trying to increase my understanding of it
>
> Do you have root? If so,
>
> rm -fr /
>
> should just about do it. :)
yes > /dev/kmem
Of course you would have to be root...
Unless the system's poorly administered (no ulimits, etc.),
crashing it from a normal user account could be difficult.
Will
Mathew A. Hennessy
Nick <goonerblo...@hotmail.com> wrote:
>Is there any kind of script or combination of commands that will crash Unix
>on a network? We cannot access the internet from our Unix server and using
>ftp between Windows & Unix is the only method of file transfer.
Easy! For a Linux system:
1) configure your own kernel, but leave out driver support for your
boot hard drive's interface or filesystem type
2) make dep && make bzImage && make modules && make modules_install
3) copy your new kernel file and system map to your boot partition
4) edit lilo.conf (assuming you use lilo) to point to your new kernel file
5) /sbin/lilo
6) reboot
You will shortly see a kernel panic!
That's how you crash a Linux kernel.
>I don't want to permanently screw up the system, just make it crash to see
>how it can be done.
Oops, you did save your old kernel, right?
Seriously, you could do a queso or nmap on the server in question and try
to figure out its OS fingerprint, then scour rootshell, securityfocus, et
al for known sploits, and hope the admin isn't too sharp.
But I never suggested that.
Cheers,
- Matt
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to be the right person today, and not put it off till tomorrow." - Larry Wall
Diar
that would eat up alot of processor usage and try and run multiple sessions,
even try multiple threaded app trying to answer the meaning of life. That
used to get all the Sysops at my college upset when some poxy 8k program was
taking up all CPU time.
This does depend on how well the Unix box is confgured, if it activly limits
CPU availability, it will be just your session tied up, and can be
terminated from the Server.
"Nick" <goonerblo...@hotmail.com> wrote in message
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Santhosh Kudva
university, Did he say crash Unix, or crash a program, collect the
core file for it and analyze it. I felt this would be more probable,
but I am shooting in the dark here. Frankly I do not see what could be
gained by putting students on this excercise if they are new to unix.
Cheers
santhosh
"Nick" <goonerblo...@hotmail.com> wrote in message news:<a6t40n$9p4$1...@knossos.btinternet.com>...
Nick
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"Santhosh Kudva" <ku...@ovation.net> wrote in message
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Paul Ng
matter how powerful the system is .. must dead
"Nick" <goonerblo...@hotmail.com> 撰寫於郵件新聞
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Nick Maclaren
In article <aa17u0$91...@imsp212.netvigator.com>,
"Paul Ng" <paul...@netvigator.com> writes:
|> Do u know the fork system call, simply call it in a never end loop, no
|> matter how powerful the system is .. must dead
Most serious Unix systems have per-user process count limits, and
will survive such things (if properly configured). There are
attacks along such lines, but you have to be a bit cleverer.