Generate White Noise using Raspberry Pi

As an alternative to listening to unwanted background noise or uncomfortable silence, create white noise with the Raspberry Pi.

Using Raspbian (other distros may vary):
apt-get install sox

Create your shell script:

export AUDIODRIVER=alsa
export AUDIODEV=hw:0,0
play -t sl - synth $len pinknoise band -n 1200 200 tremolo 20 .1 < /dev/zero

(adapted from the unreasonable man)

Backport of Aircrack-ng for Debian Wheezy

I have created a backport of aircrack-ng based on the version in Jessie/Testing. This may be installed with the command:
dpkg -i aircrack-ng_1.1-6~bpo70+1_amd64.deb
(remove the package with command: dpkg -r aircrack-ng)
download here

This package is now available in Debian wheezy-backports.

Back in March 2012 I built the latest svn version from source, available here.
I have included the necessary scripts and binary files in the ‘bin/’ directory. Copy these to somewhere like: /usr/local/sbin/

ipt_ROUTE Netfilter module ported to Linux 2.6.31

The ipt_ROUTE module became depreciated in an earlier version of Linux 2.6 – however I needed it so ported it to Linux Kernel version 2.6.31.

Disclaimer: wherever possible iproute2 should be used to achieve the desired effect.

The sources include the Kernel module and extensions to iptables.

This module and iptables extension create a new target which may be used on the mangle table.
Target usage: -j ROUTE <option>
--oif ifname - Route packet through `ifname' network interface
--iif ifname - Change packet's incoming interface to `ifname'
--gw ip - Route packet via this gateway `ip'
--continue - Route packet and continue traversing the rules. (Not valid with --iif or --tee)
--tee - Duplicate packet and route the duplicate, continue traversing the original packet. (Not valid with --iif or --continue)

I have tested the ported module on the PREROUTING and INPUT chains of the mangle table.

I use this module to route packets that have a destination IP address which matches a local IP address, out of an ethernet interface (using --oif option). These packets would normally be directed to the local system.

OpenVPN – IPv6 with tun device

Note: IPv6 is not supported using OpenVPN on Debian Squeeze (stable). The version used by Debian Wheezy (testing) supports IPv6.

Network setup:
- - Local IPv4 network
- 2001:412:abcd::/48 - Local IPv6 network
- - Tunnel IPv4 network
- 2001:412:abcd:2::/64 - Tunnel IPv6 network

I have included only the sections of config files which need ammending to enable IPv6 over OpenVPN.

Client Config
# Use the same setting as you are using on
# the server.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
dev tun
# enable ipv6

Server Config
# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap0" if you are ethernet bridging
# and have precreated a tap0 virtual interface
# and bridged it with your ethernet interface.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
dev tun0
# Enable TUN IPv6 module

# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on Comment this line out if you are
# ethernet bridging. See the man page for more info.
server-ipv6 2001:412:abcd:2::/64

# Push routes to the client to allow it
# to reach other private subnets behind
# the server. Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (
# back to the OpenVPN server.
push "route"
push "route-ipv6 2001:412:abcd::/48

# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# or bridge the TUN/TAP interface to the internet
# in order for this to work properly).
;push "redirect-gateway def1 bypass-dhcp"

# Enable to make openvpn the default route for ipv6 connectivity?
;push "route-ipv6 2000::/3"

Enabling compose key to type unicode on Linux

The compose key may be used to type unicode characters easily on Linux systems…

All of these commands should be executed as a normal user, no root access required:

  1. Identify the key you want to use as your compose key, I use the ‘Windows’ key:
    • Run the application xev
    • Press the key you want to use as your compose key
    • Note down the keycode value (my Windows key identifies as keycode=133)
  2. Edit the file ~/.Xmodmap and insert the line
    keycode 133 = Multi_key
  3. Run xmodmap ~/.Xmodmap

Restart X and you will be able to use unicode:
<Compose key> + " + u = ü
<Compose key> + ' + e = é
<Compose key> + o + r = ®
<Compose key> + - + y = ¥

and many more…

(Tested and in current use on Debian Wheezy)