Author Archives: Tom

Asterisk-oh323, GnuGK with VPoint-HD

A warning to all: audio does not work full-duplex when calling from a VPoint (VCON Emblaze) H323 client -> GNUGK -> Asterisk-oh323 -> SIP client. Tested with versions 8 and 10.

However audio works perfectly in the other direction.

The solution would appear to be to use OOH323. However the audio is again half duplex in the scenario where SIP clients are calling H323 clients.
Therefore calls originating from Asterisk to H323 clients use the ‘OH323’ module, and calls from GNUGK into Asterisk use the ‘OOH323’ module.

Linux CPU Scaling Governor – Performance and Overheating

On my previous laptop I suffered with repeated over-heating problems whenever CPU load went high for a prolonged period. After several emergency shutdowns (performed by ACPI) I discovered the problem:

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

returned the result: “performance”

Inserting the following line before the ‘exit’ line in /etc/rc.local:

echo "conservative" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

resolved the problem.

For all available scaling governors:

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors

Bash Scripts – exit on immediate fail

With some bash scripts it can be useful to have them exit as soon as a command fails. To accomplish this have the following just after the “#!/bin/bash” line:

set -o errexit

This will cause the script to exit as soon as any command or program returns an exit status not equal to zero.
Thanks to Rory.

Skype, Linux and NFS

A problem I found when using the Linux client for Skype is that it will try to perform file locking, which is a problem if your home partition is an NFS drive.

To overcome this limitation, create a directory on the local hard disk:

sudo mkdir /usr/local/skype
sudo chown tom.tom /usr/local/skype

Delete the configuration that Skype attempted to install, and symlink to the directory on the local harddisk:

rm -rf /home/tom/.Skype
ln -s /usr/local/skype /home/tom/.Skype

After this Skype worked as normal.

Checkinstall – easy way to build RPM and Deb packages

Thanks to the kind people in #asterisk (irc.freenode.net) I found: Checkinstall

This is a very quick and easy was to make your own RPM and Deb packages. When compiling your package, instead of running “make install” run: “checkinstall”

To build for most distributions, the configure script should be executed with the following options:
./configure –prefix=/usr –sysconfdir=/etc
so that executables, libraries and configuration files are installed to the expected locations.

Tom Salmon

Linux & Networking