I killed my system with grep

Loren M. Lang lorenl at alzatex.com
Fri Feb 25 13:57:16 GMT 2005

On Fri, Feb 25, 2005 at 12:14:04PM +0100, Ramiro Aceves wrote:
> Hello FreeBSD friends:
> I am running a FreeBSD 5.3 system with 64MB RAM and 150 MB swap.
> Yesterday I entered the command:
> # grep -R something /

Running a grep on an entire system as root is a bad idea.  At least
limit to certain filesystems.  You probably hit a file under /dev/ and
caused grep to hang.  It's possible that as root, certain device files
might hang the system, but nothing comes to mind at the moment unless
/dev/io could do it.  Also, think about what happens when grep hit's
/dev/zero.  It will never finish.

> and after a while, my system did not respond. I do not remember the exact
> messages as I am on a winbugs at the University. The error was about
> swapping. I could switch among terminals but the system was dead. I needed
> to reboot.
> I rebooted and tried again watching "top" output and I could see as swap
> usage was incresing very quickly until it ran out of swap space and the swap
> pager failed.
> Was my sytem dead? or, is it possible to recover from that state without
> rebooting? How is it possible that a simple command like this could
> auto-kill the machine?
> What is the recomended fix for this?:
> a- Asigning more swap.
> b- Not executing that command anymore.
> Thank you very much for your advices and help.
> Ramiro
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I sense much NT in you.
NT leads to Bluescreen.
Bluescreen leads to downtime.
Downtime leads to suffering.
NT is the path to the darkside.
Powerful Unix is.

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