"Funny" bash command
Adam Visegradi
:(){ :|:&};:
It kills my computer in an eyeblink :D Mem usage climbs up to the
maximum and everything get unresponsive -- even the mouse stops moving.
Thx.
Sasquatch Brohan
Sasquatch Brohan
2) perl -e 'while(1 == 1) { fork; }'
3) Wait for the system to crash to its knees. If it doesn't entirely lock up within a matter of seconds, you probably have ulimits enabled.
Mirko
It's a logic bomb writen in bash. Here's a more readable version:
function bomb ()
{
# use a pipe to invoke a new shell recursive
bomb | bomb & ;
}
Now, when you call this little devil, it will recursivly execute a new
shell running bomb, resulting in thousands of processes running. This
fires up your CPU load to 100% and fills up your memory.
Jeremiah Bess
Adam Visegradi
unfortunately there is a colon command -- it does nothing. I would've
never think of that the colon is the function's name. LOL
Thanks!
PS.: Jeremiah! How do you do that you're the only one whose message is
"empty" when I recieve it via GMail. I always get only the quoted part
:)
On 1/22/07, Mirko <mka...@gmx.net> wrote:
>
--
Adam Visegradi
-----BEGIN GEEK CODE BLOCK-----
GCS/M a-- s+: dpu>d+ C++(++++)
UL++>+++ L+++>++++ W++ E(---) P+ N++
R !tv b+ D+ G++ e>++++ h-- r++ y++
------END GEEK CODE BLOCK------
Jeremiah Bess
--
Jeremiah E. Bess
Network Ninja, Penguin Geek, Father of three
Mirko
I am not 100% sure if my this explation is completly correct, but for
all I know:
When using a pipe, the command in the left side of the pipe is executed
in a newly spawned sub-shell. By adding & to the rigth hand side, this
command get's also executed in a sub-shell. While your perl solution
just forks _one_ new process in every iteration, this bash beast forks
_two_ processes on each iteration. Consequently, both of the bomb
invocations will also spawn two sub-shells, resulting in 2, 4, 8, 16,
... running processes after the first, second, third fourh, ...
iteration.
This means, that after the 32. iteration, the perl script will have
spawned 32 processes, while the bash script will have spawned
4294967296 shells!
So even on a super-duper furture super-computer with several penta
bytes of RAM, this will fill up the memory in just some seconds.
Adam Visegradi
be ended. After spawning a new process, the spawner continues the
iteration, so do its children and their children etc.
Assuming the iterations are synchronized, after the Nth there will be
2^N processes running -- the two methods have the same efficiency :)
I prefer a hammer. It has premanent effect.
On 1/22/07, Mirko <mka...@gmx.net> wrote:
>
Mirko
Adam Visegradi schrieb:
> The fork method is exponential too. The fork doesn't wait the child to
> be ended. After spawning a new process, the spawner continues the
> iteration, so do its children and their children etc.
> Assuming the iterations are synchronized, after the Nth there will be
> 2^N processes running -- the two methods have the same efficiency :)
> I prefer a hammer. It has premanent effect.
Ahh, thanks for the correction! :)
I don't use perl much, so it looks as a plain linear iteration to me.
Sasquatch Brohan
Suren Karapetyan
working as needed(you'll still be able to ping the box)
And if you give the right nicelevels your web server will continue running too.
And even if you don't give any limits for the users, the kernel will
finally decide that the process is broken and kill it (well.. in fact
it may decide to kill some other process to free up memory)
For example you may make all the users login with 10 nicelevel.
Sasquatch Brohan
Suren Karapetyan
Even ran it miwth the highest nicelevel (lowest priority) it doesn't
take even a second to Destroy "X". I even managed to ask a friend of
mine to run this on hist half-dedicated server....And you know what?
It stoped all 5 of his sites from running and all the other site on
the same server. It took him an hour to bring the server back to life.
I'm not quite sure I understand why this can harm the system when run
with low priority.
On 1/22/07, Adam Visegradi <a.vis...@gmail.com> wrote:
>
Jeremiah Bess
Mirko
On Feb 2, 9:29 pm, "Jeremiah Bess" <jeremiah.b...@gmail.com> wrote:
> On 2/2/07, Suren Karapetyan <surenkarapet...@gmail.com> wrote:
>
>
>
> > Retested this thing a bit more....
> > Even ran it miwth the highest nicelevel (lowest priority) it doesn't
> > take even a second to Destroy "X". I even managed to ask a friend of
> > mine to run this on hist half-dedicated server....And you know what?
> > It stoped all 5 of his sites from running and all the other site on
> > the same server. It took him an hour to bring the server back to life.
> > I'm not quite sure I understand why this can harm the system when run
> > with low priority.
>
> > On 1/22/07, Adam Visegradi <a.visegr...@gmail.com> wrote:
>
> > > Can anybody explain this bash command to me?
> > > :(){ :|:&};:
>
> > > It kills my computer in an eyeblink :D Mem usage climbs up to the
> > > maximum and everything get unresponsive -- even the mouse stops moving.
>
> > > Thx.
>
> I think you just lost faith and credibility from your friend. =( Hope you
> guys can patch your friendship soon! lol. Good story though.
Hmm, no admin should run such script without being aware of possible
consequences. ;)
Good story, anyway, yes.
I'm not sure about it. I didn't used nice much. But I suspect, that
even with high-nice, some million processes are just too much to
handle.