试了一下 rm -rf / :D

root@www:~# uname -a
Linux web 3.4.0-cloud #1 SMP Thu May 24 05:12:36 EDT 2012 i686 GNU/Linux
rot@www:~# lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 6.0.4 (squeeze)
Release: 6.0.4
Codename: squeeze
root@www:~# rm -rf /
rm: it is dangerous to operate recursively on `/'
rm: use --no-preserve-root to override this failsafe
root@www:~# rm -rf --no-preserve-root /
^Z
[1]+ Stopped rm -rf --no-preserve-root /
root@www:~# bg
[1]+ rm -rf --no-preserve-root / &
root@www:~#
root@www:~# rm: cannot remove `/boot': Device or resource busy
...