Saturday, January 31, 2009

Getting the public key of a ubuntu repository

I sometimes have problems when I add an APT line to the source.list and when I do and apt-get update, get an error message saying I do not have an authentication key, especially from one of the repositories. The usual message would be:

GPG error: intrepid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0123456789ABCDEF

I have a short script that can help you get the correct key. Simply create a file called and type in the following code:

gpg --keyserver --recv $1
gpg --export --armor $1 | sudo apt-key add -

You then have to make the file an executable file, this can be done by using the chmod command with the +x switch:

chmod +x

To import the signature, simply type:

./ 0123456789ABCDEF

The above assumes the script is located in the current directory and the repository's public key is located on the server.

Wednesday, January 28, 2009

Installing Ubuntu 8.10 on my EeePC 701...

Got myself a 16GB class 4 SDHC card and decided to upgrade my EeePC 701 with the latest version of Ubuntu (8.10 Intrepid).

I used a DVD drive to install Ubuntu on my EeePC and almost everything worked OOTB (out of the box) with the exception of wifi and a shutting down problem.

To fix the first problem, I disabled the "Support for Atheros 802.11 wireless LAN cards" on Hardware Drivers, and rebooted.

Then, I installed the backports modules which has a working wifi driver by typing the following in a terminal shell:

sudo apt-get install linux-backports-modules-intrepid-generic

Before anyone asks... Yes, I had to do this with a wired internet connection.

To solve the shutdown problem, all I had to do was to edit the "halt" file at "/etc/default/" and add in "rmmod snd-hda-intel" on the last line of the file.

This basically gets the whole computer working as everything else is already supported by Ubuntu.

To enhance the computer, I also installed a utility called Eee Control. The latest version as of this writing is v0.8.3. You can get this utility at URL

This utility allows you to control the switching on/off of certain components like wifi, camera, etc. You can also overclock or underclock the EeePC with the option to auto powersave when your EeePC runs off batteries regardless of the clock speed when plugged to the wall.

To increase the lifespan of the SSD (or SDHC card in my case), we can reduce the frequency of writes to the media by adding the following into the "/etc/fstab":

tmpfs /var/tmp tmpfs noatime 0 0
tmpfs /tmp tmpfs noatime 0 0

You can also add the "noatime" to the other medias that Ubuntu accesses.

Installing the Firewalk security tool

Unfortunately for all, the firewalk tool is not found in any of the Ubuntu repositories nor is there a .deb file that you can download and install. You will need to download the source code and compile the program yourself.

To get the firewalk source, go to URL Download the source file from the site called "firewalk.tar.gz". You then need to untar the file by typing in a terminal shell:

tar -xvvzf firewalk.tar.gz

This will untar all the files and create their respective directories. You will then need to install the relavent supporting libraries and their development tools with the command:

sudo apt-get install build-essential libpcap-dev libnet1-dev libdnet-dev libdumbnet-dev

Since this tool (firewalk) was developed a few years ago, two of the libraries it uses have changed their names, we will need to link the old name to the new object name with the following sequence of commands:

cd /usr/lib
sudo ln -s
cd /usr/include
sudo ln -s dumbnet.h dnet.h

Before you can compile firewalk, there is one change you will need to make to the source. Gutsy (and newer Ubuntu distros) install gcc 4.0 by default, which doesn't like switch statements with no instructions in the "default" case. To fix this, just insert the "break;" command on line 193 of src/firewalk.c:

==== old =====

/* empty */

==== new =====

/* empty */

Now, you are ready to compile everything, issue the following commands in the Firewalk directory:

sudo make install

To install the man pages, type in the following:

sudo mkdir /usr/local/man/man8
sudo cp man/firewalk.8 /usr/local/man/man8

You are now ready to use the firewalk utility command. :)

Note: This was done on a Ubuntu 8.10 distro.

Tuesday, January 27, 2009

Life with Ubuntu

Just started this blog today as I wanted to write about how easy it is to use Ubuntu Linux. I will only write about what I do, use, experience and think about Ubuntu (for now) and hopefully help and assist others on this journey as well. A little background, I have been using Ubuntu for the last 4 years (since Ubuntu 5.04) and use Ubuntu on all my own PCs with the exception of my laptop which I use in the office that has Windoze XP (with wubi and Ubuntu 7.10). One of my laptops is an EeePC 701 so you will also read a bit of Eee centric posts as well as security applications which I use for work. More to come in the following days... :)