An old PC used as an A2DP bluetooth receiver

Works for me with Linux Mint 12.

The tutorials I found explain the part where we must add

Enable=Source
in /etc/bluetooth/audio.conf

but I had a hard time to figure out that I had to modify /etc/pulse/default.pa and add
load-module module-switch-on-connect
load-module module-loopback

else the sink/source are not automatically connected.

Manages Linux devices with HAL

HAL, the Hardware Abstraction Layer of most recent Linux distros really is an impressive piece of architecture.

I'm impressed by how easy it is to take control of any low level parameter of any hardware.

Two example I've recently used :

A workaround to prevent nautilus in Ubuntu 9.04 from automatically mounting my MTP player :
I've added a no-automount.fdi file in directory /etc/hal/fdi/policy<br /><?xml version="1.0" encoding="UTF-8"?> <!-- -*- SGML -*- --><br /><deviceinfo version="0.2"><br /> <device><br /> <match key="info.product" string="ZEN V Plus"><br /> <remove key="info.capabilities" type="strlist">portable_audio_player</remove><br /> </match><br /> </device><br /></deviceinfo><br />(See my answer "stephg said on 2009-11-09" in this post for more details)

An other example to slow down the cursor speed of my high resolution mouse. As the xorg configuration file is not used anymore in Ubuntu, the X11 options can be set with a HAL configuration file.
I've added a 10-x11-input.fdi file in directory /etc/hal/fdi/policy : <br /><?xml version="1.0" encoding="UTF-8"?> <!-- -*- SGML -*- --><br /><deviceinfo version="0.2"><br /> <device><br /> <match key="info.product" string="Logitech USB Laser Mouse"><br /> <merge key="input.x11_options.ConstantDeceleration" type="string">2</merge><br /> </match><br /> </device><br /></deviceinfo><br />This "merge" scheme really is brilliant because it allows to go back to a default configuration by deleting a file.

Mix RJ45 and coaxial (10Base-2) ethernet cables

Problem : how do you add a WIFI AP (Access Point) to an already existing network wired with 10Base-2 coaxial ethernet cables ?

Of course this is an old network with old PC, and you can not replace the 10Base-2 network adapters of the PC in order to rewire with RJ45 cables.

Answer : just find one more 10Base-2 network adapter in a drawer, and add it in an old Linux box that already has a RJ45 network adapter.

Setup two subnetworks, one on each adapter of the Linux box, with routing of the traffic from one subnetwork, to another (or even better, build a bridge, in order to have one single subnetwork).

Plug in the AP to the linux box with a crossover RJ45 ethernet cable.

This linux box can even be used as a gateway both for the LAN and for the WLAN !

Simple iptable gateway script

It's the second time I must setup a Linux gateway connected to a DSL line. The DSL modem interface is ppp0 and the LAN interface is eth0. Here is the script I use to setup the iptables :

<br />echo "1" > /proc/sys/net/ipv4/ip_forward<br /><br />modprobe ip_conntrack_ftp<br /><br />export EXT=ppp0<br /><br />/sbin/iptables -F<br />/sbin/iptables -t nat -F<br />/sbin/iptables -t mangle -F <br />/sbin/iptables -X <br /><br />/sbin/iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT<br />/sbin/iptables -A INPUT -m state --state NEW -i ! $EXT -j ACCEPT<br />/sbin/iptables -P INPUT DROP<br /><br />/sbin/iptables -A FORWARD -i $EXT -o eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT<br />/sbin/iptables -A FORWARD -i eth0 -o $EXT -j ACCEPT<br /><br />/sbin/iptables -t nat -A POSTROUTING -o $EXT -j MASQUERADE<br /><br />/sbin/iptables -A FORWARD -i $EXT -o $EXT -j REJECT<br />

Linux and Logitech MX mouses resolution

Without its real driver, my Logitech MX 510 mouse is seen by Linux as a 400 cpi resolution mouse. Actually it can be used in 800 cpi thanks to lmctl

I've added this script to the 'Startup Program' list of Gnome :
<br />#!/bin/sh<br />lmctl -8<br />xmodmap -e "pointer = 1 2 3 4 5 8 9 6 7"<br />
The xmodmap call allows to properly configure the thumb buttons.