Some older presentations I have given can be found here.

The all deal with DNSSEC - note that most of them have been written a few years ago.

As any long time computer addict will tell you, (computer) cables are a pain in the butt. They collect dust and generally look bad. So ever since I worked for BIT I wanted to clean up my cable mess at home. Yesterday I finally started... only a year after I have left BIT.

hardware

I've bought a roll of velcro (5 m and 25 mm wide)

and some fitcoflex (25 m and 50 mm wide)

at display.nl. It wasn't cheap, but I think it is worth the price. Also I've been using ty-rap's, but I think velcro is much better as you can easily unty them.

first project

As a first attempt to get a feel for the material I wanted to clean up my computer and bundle some SATA cables and power lines. As I was too hasty I don't have any before photos...only the after shots.

Well here is how it looks now

Trust me; this is better than it has ever looked!

closing remarks

Cutting the Fitcoflex is not that easy, and you want to use some lighter to burn the ends so that it will not split too easy.

And of course I had to mess with the system WHILE it was running, resulting in a shutdown of my raid disks -- all three of them. I accidentally pulled the power cable from the disks.

Next up: cables behind my computer(s).

Completely forgot the name and where you could find it. I had a lot of fun with this game more than a year ago. So for future generations here it is.

Google is always helpful of course, so I've found this blog entry on how to set the background in xfce.

It boils down to setting a jpg in XFCE's backdrops.list and then reloading xfdesktop. Crude, but it works.

This can de done with the following command:

cat <<EOF > ~/.config/xfce4/desktop/backdrops.list
# xfce backdrop list
background.jpg
EOF

And then

xfdesktop --reload

However when running from CRON it is more easy to do a killall -USR1 xfdesktop.

A collage from ATComputing, Jacques loonen had a little script that will download a nice image from some site showing the earth with actual clouds rendered on it. I'm going to use it to make a background that slowly changes from day into night and vice verse.

The following script wil be run from cron, it will generate a new jpg suitable for background use. Images from opentopia.com are particularly nice.

#!/bin/sh
IMG=/home/miekg/tmp/xfce_bg.jpg
wget \
http://www.opentopia.com/images/cams/world_sunlight_map_hemisphere.jpg \
-O $IMG 
# not really needed, but... heh
cat <<EOF > ~/.config/xfce4/desktop/backdrops.list
# xfce backdrop list
$IMG
EOF
killall -USR1 xfdesktop

The # xfce backdrop list comment seems to necessary to make it all work.

CRON

CRON is the most natural fit to download new images. So save the script to a place where it can be found, say in ~/bin/xfcebg and edit your user cron entry with crontab -e and put something like this in there

*/5 * * * *       $HOME/bin/xfcebg

That's it!

Didn't like it

The whole scaling seems to be a bit off and the earth image is way too white, so I'm already back on my go'old background :-)

After playing with Linux for 12 years, I have now been LPI-1 certified. It wasn't really difficult, but you still need to know a lot of details.

Next up: LPI-2 (if it is needed for my lessons)

Working on backup programs for almost a decade now, I've had plenty of time to think about file system wrt backups. Basically I want the following properties in a file system

• online snapshots in a .snapshots directory (for instance).
• the possibility to say the all those .snapshot directories must be mounted on a separate mount point.
• to ability so say the .snapshot directories should be encrypted and send to remote server.

I think this is too much to ask...

The new kernel for the EeePC (2.6.25) has deprecated the /proc/acpi/battery interface, so I had to write a new script for use in my zsh prompt.

The script will work in both 2.6.24 and 2.6.25, so without further ado, here it is. It is written as a function for easy inclusion in any prompts.

#!/bin/zsh 
bat() {
PROC=/proc/acpi/battery/BAT0
SYS=/sys/class/power_supply/BAT0/uevent
STATE=
# dc: design capacity, rc: remaining capacity
if [ -f $PROC/info ]; then
    STATE=$PROC/state   # 2.6.24
    dc=$(grep 'last full' < $PROC/info | awk '{ print $4 }')
    rc=$(grep 'remaining' < $PROC/state | awk '{ print $3 }')
elif [ -f $SYS ]; then
    STATE=$SYS          # 2.6.25
    dc=$(grep '\<POWER_SUPPLY_CHARGE_FULL\>' < $SYS | awk -F= '{ print $2 }')
    rc=$(grep '\<POWER_SUPPLY_CHARGE_NOW\>' < $SYS | awk -F= '{ print $2 } ')
else
    exit
fi
p=$(echo 3k $rc $dc / 100 \* p | dc )

if grep -iq discharging $STATE; then
    printf " %02d" "$p"
else
    if [ ${p%.*} -lt 100 ]; then
    printf " %02d+" "$p"
    fi
fi
}
bat

Update

Ton Kersten has an even better one which saves a few greps.

#!/bin/zsh 
bat() {
PROC=/proc/acpi/battery/BAT0
SYS=/sys/class/power_supply/BAT0/uevent
STATE=
# dc: design capacity, rc: remaining capacity                                                                           
if [ -f $PROC/info ]
then
    STATE=$PROC/state   # 2.6.24
    dc=$(awk '/last full/ { print $4 }' $PROC/info)
    rc=$(awk '/remaining/ { print $3 }' $PROC/state)
elif [ -f $SYS ]
then
    STATE=$SYS          # 2.6.25
    dc=$(awk -F= '$1 ~ /^POWER_SUPPLY_CHARGE_FULL$/ { print $2 }' $SYS)
    rc=$(awk -F= '$1 ~ /^POWER_SUPPLY_CHARGE_NOW$/  { print $2 }' $SYS)
else
    return 0
fi

p=$(echo 3k $rc $dc / 100 \* p | dc )

if grep -iq discharging $STATE; then
    printf " %02d" "$p"
else
    if [ ${p%.*} -lt 100 ]; then
    printf " %02d+" "$p"
    fi
fi
}
bat

Update 2

Just found that there is also a nice tool, called acpi...which makes it even more easy:

% acpi -V
Battery 0: Full, 100%
AC Adapter 0: on-line
Thermal 0: ok, 53.0 degrees C
Cooling 0: Processor 0 of 7

The previous rdup roadmap has been implemented. I'm now working on the post 0.6.1 items and added a few new features:

• The regular expressions are now pcre (Perl Compatible Regular Expressions), this adds an extra dependency to rdup for this library. But these are so much more powerful that I think it is worth it.

• For completeness sake I added: sockets, named pipes, character devices and block devices as recognized file types to rdup. One side effect of this is that the filesize (%s) is (again) overloaded to mean minor,major just as in the ls -l output when an character or block devices is printed.

  The rdup-utils currently ignore these extra file types.

  So lets say I have this directory:

  
  $ ls -l A
  total 0
  -rwsrwsr-x 1 miekg miekg    0 Aug 11 12:45 blaat*
  -rw-rw-r-- 1 miekg miekg    0 Aug 11 16:30 ff
  prw-rw-r-- 1 miekg miekg    0 Aug 11 16:34 fifo|
  brw-r--r-- 1 root  root  8, 0 Aug 11 16:24 sda
  crw-r--r-- 1 root  root  8, 0 Aug 11 16:24 sdb
  srwxrwxrwx 1 miekg miekg    0 Aug 11 16:58 socket=
  

  rdup will now print this as:

  
  ./rdup /dev/null A
  +d 0755 0 0 5 0 /home
  +d 0751 1000 1000 11 0 /home/miekg
  +d 0711 1000 1000 15 0 /home/miekg/svn
  +d 0700 1000 1000 20 0 /home/miekg/svn/rdup
  +d 0775 1000 1000 26 0 /home/miekg/svn/rdup/trunk
  +d 0775 1000 1000 28 0 /home/miekg/svn/rdup/trunk/A
  +- 6775 1000 1000 34 0 /home/miekg/svn/rdup/trunk/A/blaat
  +- 0664 1000 1000 31 0 /home/miekg/svn/rdup/trunk/A/ff
  +p 0664 1000 1000 33 0 /home/miekg/svn/rdup/trunk/A/fifo
  +b 0644 0 0 32 8,0 /home/miekg/svn/rdup/trunk/A/sda
  +c 0644 0 0 32 8,0 /home/miekg/svn/rdup/trunk/A/sdb
  +s 0777 1000 1000 35 0 /home/miekg/svn/rdup/trunk/A/socket
  

  So there as 4 new types: p, b, c and s.

• The move to GNode might be needed to allow rdup to reverse print the filelist (i.e. rdup /dev/null ~/bin | tac). In 0.6.2 a -R flag is added that makes this possible. The internal structures in rdup are still GTree's (balanced binary trees). The -R feature is implemented by putting all elements in a linked list (GList) and reverse printing that.

You want to clean up /usr/share/doc every time you install a package to safe space. Here is how to do it.

Completely inspired by localepurge (and I stole some code from it).

But I wanted to purge stuff in /usr/share/doc/$package too as this takes too much disk space on my precious (talking about the EeePC here). If I really need the documentation I will also install the package on my server and look at it there.

localepurge consists out of two important parts, a hook for dpkg which is called after each installation. This hook is placed in /etc/apt/apt.conf.d. And a script that will actually remove the locales (/usr/sbin/localepurge).

For my needs a actually need to tweak the hook a little and write a little script. My first thought was to actually look at the package being installed and only remove the doc-dir for that package, but a quick search yielded no clue on how to give the name of the package to DPkg::Post-Invoke. So the next best thing I could come up with was to delete everything in /usr/share/doc every time.

DPkg::Post-Invoke

The Post-Invoke from localepurge looks like this:

DPkg
{
Post-Invoke {"if [ -x /usr/sbin/localepurge ] && [ $(ps w -p "$PPID"
    | grep -c remove) != 1 ]; then /usr/sbin/localepurge; else exit 0; fi";};
};

This needs to be tweaked a little for my purposes. I'm storing the scripts in the dir /home/miekg/bin -- as I'm the sole user of my EeePC.

DPkg
{
Post-Invoke {"if [ -x /home/miekg/bin/docpurge ] && [ $(ps w -p "$PPID"
    | grep -c remove) != 1 ]; then /home/miekg/bin/docpurge; else exit 0; fi";};
};

Save this file in /etc/apt/apt.conf.d as 99-docpurge.

docpurge

I've named my script docpurge and its a stupid script that just deletes stuff in /usr/share/doc. For completeness here it is:

#!/bin/bash
# delete stuff in /usr/share/doc

DOCDIR=/usr/share/doc
for i in $DOCDIR/*; do
rm -rf $i
done

After some switching I have now settled on XFCE. With Ubuntu XFCE sometimes does not start, this is a dbus issue in combination with gnome-screensaver (a race condition between the two). This sucks, but can be resolved easily with

apt-get remove gnome-screensaver

(There aren't any interesting option anyway...)

So my XFCE is now up and running, time for some tweaking.

In the quest for precious vertical pixels (especially on the EeePC 701 I own) I decided I must remove those pesky title bars.

I found prelude-4.0 which is beautiful, but it make it kinda hard to see which window is active. That's why I've modified it slightly to have a blue-ish border (at the left, bottom and right) when a window is active. Just enough to give you a subtle visual hint. You download my variation (which is called premiek for lack of a better name) from here.

Further more my gtk theme is Mist, a simple theme that is much quicker (i.e. takes less resources) than for instance Clearlooks.

Take a look at the following screenshots. Click on them for larger views.

Firefox with some gnome-terminals:

Thunar with terminals and a gvim session:

rdup 0.6.1 just got released a few days ago. It fixes some bugs and has the rdup-s3 utility.

Go to the project page and read more or download it right away.

Grrrrr

cd
rm -rf Desktop
mv Documents docs

I don't want desktop environments messing with MY home directory.

Thank you.

I've battled with amavis too often and I started to dislike it a little. So when I wanted to configured my postfix setup to scan for viruses and spam and needed a solution which would work without amavis.

This is what I came up with.

debian administration was kind enough to do the hard work, but this is only the setup for clamav and I also want to spam scan.

packages

First install the packages you will need

apt-get install spamassassin spamc clamav clamsmtp

configuration

This is where I followed the 'Debian administration' article, in /etc/clamsmtpd.conf you must have

Listen: 127.0.0.1:10025
OutAddress: 10026

You could also change:

# A header to add to all scanned email
Header: X-AV-Checked: ClamAV using ClamSMTP (elektron.atoom.net)

to add your own header to see if the scanning is working.

For postfix you must have a few lines in /etc/postfix/main.cf that read

# virus scanning
content_filter = scan:127.0.0.1:10025
receive_override_options = no_address_mappings

This is only for virus scanning, for spam scanning you will need to tweak /etc/postfix/master.cf also

# interface to spamassassin. 
spamassassin unix - n   n   -   -   pipe
    user=nobody argv=/usr/bin/spamc -f -e
    /usr/sbin/sendmail -oi -f ${sender} ${recipient}

This will feed the mail directly to spamc.

test it

/etc/init.d/clamsmtp restart
/etc/init.d/spamassassin restart
/etc/init.d/postfix restart

That's it!

I've written quite a few LaTeX documents during the last few years, but only recently I'm starting to discover very powerful new packages, like memoir and xelatex.

So I just wanted to share my "new" way of writing LaTeX docs.

First read the memoir class documentation. And the fontspec doc.

preamble

This now looks like

\documentclass{memoir}
\usepackage{eurosym}    %% for the EURO
\usepackage{fontspec}   
\usepackage{xltrxta}    %% \XeTeX if you need it

Usually this is hidden in one of my class files which implement a new look for a document. See the following articles for some examples

• atroff style
• blocksbook style

example

This is a small example on how to use XeTeX

\documentclass{article}
\usepackage{fontspec}
\begin{document}
Testing XeLaTeX!

\fontspec[Scale=0.9]{Trebuchet MS}
Something in trebuchet, but too large

\fontspec[Scale=MatchLowercase]{Trebuchet MS}
Size adjusted to the rest of the text!

\LaTeX rules

\rmfamily
\LaTeX in the normal font
\end{document}

Generate the pdf with

xelatex example.tex

xelatex is my new friend now :)