mtg

Old content, lovingly restored

2026-10-27T21:00:00+00:00

The old content on this blog comes from my blog called “The Empty Quarter” which was hosted on martinhammer.com roughly between 2009 and 2020. The purpose of that blog was to record little how-to snippets and links mainly to do with Ubuntu and Linux in general, and BIRT which is a tool I was using at work at the time. There isn’t much value in the content from a technical point of view; from the curiosity perspective it is perhaps an interesting look back in time.

The content was restored from an old WordPress backup. The posts were converted into Markdown with the help of Claude AI. This site is built using the Zola static site generator, using those Markdown files as input.

SublimeText on Ubuntu 16.04

2016-08-07T15:40:28+00:00

For some reason Unity in Ubuntu 16.04 and the SublimeText deb package don’t play well together and the integration is not quite right - for one the launcher says “UNREGISTERED” even after entering a valid licence key, and SublimeText does not appear in Nautilus context menu as an option to open files. Here’s the workaround for this issue.

The right way to set PATH variable

2016-07-15T06:17:58+00:00

Great post on Stack Exchange, How to correctly add a path to PATH?.

Network Manager woes in Ubuntu 16.04

2016-07-15T06:12:40+00:00

Lots of issues with Network Manager in Ubuntu 16.06 LTS, in particular connecting to wifi after suspend/resume. Restarting the Network Manager service seems to work for me.

sudo systemctl restart network-manager.service

Fix for Nautilus shows hidden files by default

2016-01-26T04:05:15+00:00

Here’s the fix for a problem where Nautilus shows hidden files by default.

$ dconf-editor
org -> gtk -> settings -> file-chooser
Uncheck show-hidden
Close Nautilus and open again

Crayon Syntax Highlighter

2014-10-26T06:36:05+00:00

I have just installed the Crayon Syntax Highlighter plugin on this blog. Obviously a lot of the posts that I put here contain code snippets, so this great plugin will make that a little neater with feauters such as line numbers toggle, syntax highlight, copy into clipboard and many more. Over time I hope to update the existing content on the site to make use of the plugin.

Transpose rows to columns using awk

2014-10-18T15:50:47+00:00

In this post we look at how text data can be transposed in a shell script. Suppose you have a comma-delimited text file (csv) which looks like this:

2014-10-01,Reading1,20.3
2014-10-01,Reading2,21.5
2014-10-01,Reading3,24.0
2014-10-01,Reading4,22.2
2014-10-02,Reading1,20.5
2014-10-02,Reading2,21.5
2014-10-02,Reading3,24.1
2014-10-02,Reading4,22.4
2014-10-03,Reading1,20.5
2014-10-03,Reading2,21.7
2014-10-03,Reading3,24.2
2014-10-03,Reading4,22.5

…and so on. Perhaps this is a set of sensor readings over a period of time, and in this case there are four readings per day. For further analysis it might be more suitable to store each date on a single line with the four readings as columns. In other words we want to transpose rows to columns, i.e. pivot the values on date. The file should look like this:

2014-10-01,20.3,21.5,24.0,22.2
2014-10-02,20.5,21.5,24.2,22.4
2014-10-03,20.5,21.7,24.1,22.5

Since this needs to process multiple input rows of to produce one output row, sed will not be suitable. Instead we need to use awk. The following tiny script will do the trick.

$ awk -F, '{val = val "," $3; if( NR % 4 == 0 ) { print $1 val; val = "" } }'

Now, what exactly is this doing? First, we need to specify that the file is comma delimited, which is what -F, does. Next, the main principle is that the code stored between the curly brackets will be executed individually for each row, however a session (including variables) is maintained throughout the execution of entire input. So val is a variable into which we are storing the third field on each row ($3) prepended by a comma. The if statement checks whether the row number (NR is a special built in variable which holds the number of the row being currently processed) is divisible by four (% is the modulo function, as in most languages). If yes, we print the date which is the first column ($1) as well as the val variable which now has the values from the previous three rows as well as this one, separated by commas. The variable is then reset.

Obviously, we are making an assumption here that the data is uniform, i.e. that there are exactly four readings available for each day; otherwise the script would be a little more complex.

Tar gotcha: extract from multiple tar files in one go

2014-10-18T07:48:47+00:00

Suppose you have a monthly process to archive some data such as log files etc. Each month a separate archive file is created, and so after a few months you will have several archive files - for example as shown below:

archive.2014-08.tar.gz
archive.2014-09.tar.gz
archive.2014.10.tar.gz

Now if you wish to extract your data from all three files, you could run individual commands such as:

$ tar -zxvf archive.2014-08.tar.gz
$ tar -zxvf archive.2014-09.tar.gz
$ tar -zxvf archive.2014-10.tar.gz

This works fine. However the following won’t work if you want a one-line which does them all in one short:

$ tar -xzvf *.tar.gz
tar: archive.2014-09.tar.gz: Not found in archive
tar: archive.2014-10.tar.gz: Not found in archive

Basically the way that tar command works, if more than one filename (or an expansion) is passed as an argument, it will look for the second, third, etc. files inside the first file. So the error is saying it cannot find the second and third archive file inside the first one (archive.2014-08.tar.gz). So in essence the tar command itself really does have to be called individually for each file. The way to simplify this on a one-liner is to use the xargs command which will do exactly that:

$ ls *.tar.gz | xargs -n1 tar -xzvf

Fingerprint authentication in Ubuntu

2013-10-25T04:56:10+00:00

FPrint is a PPA with packages for fingerprint-based authentication. Website includes good documentation on how to install and set it up.

Remove old kernels and free up space in /boot partition

2013-10-16T08:39:04+00:00

This is a great one-liner which removes old kernel images and frees up space in your boot partition:

$ sudo apt-get purge $(dpkg -l linux-{image,headers}-"[0-9]*" | awk '/ii/{print $2}' | grep -ve "$(uname -r | sed -r 's/-[a-z]+//')")

This comes from the top answer to a question on ask ubuntu.

Reorder accounts in Thunderbird

2013-09-20T05:15:23+00:00

Here’s an article on Lego’s Land on how to reorder accounts in the left pane of Thunderbird.

Command line on Nokia N900

2012-08-16T13:39:34+00:00

The Nokia N900 is getting a little old now, but it still an amazing piece of kit. This post has a few pointers for making the most out of command line usage it enables.

Command Line Execution Widget: This widget lets you run commands from the desktop and outputs the results..
Cmd Shortcuts: Allows you to quickly run your own defined commands.
gPodder: This excellent podcast catcher comes with a command line interface. Run gpo from the terminal to get the full list of options.
FeedingIt: This RSS aggregator can be run from the command line. The known options are /usr/bin/FeedingIt update and /usr/bin/FeedingIt status.
Alarmed: This is a graphical interface to the cron scheduler. Apart from neat access to phone functionality (e.g. switching profiles, networking, and yes alarms) it also allows arbitrary shell commands to be scheduled. This is particularly useful with the gPodder and FeedingIt mentioned above. To use this tool you currently need to enable the testing repository.

Read and edit JPEG Exif data from command line

2012-08-11T05:41:47+00:00

Most digital cameras store Exif data in the JPEG photo files. This includes things like date and time, camera model and camera settings and in some cases even GPS coordinates. jhead is a very useful command line utility which can read and edit the Exif data. For example, you may wish to remove the data from photos published online.

Another useful thing is to rename photos using the date and time information stored in Exif (note: read the documentation before running):

$ jhead -n%Y%m%d-%H%M%S *.jpg

And best of all jhead is in the Ubuntu universe repository, so installing it is as simple as:

$ sudo apt-get install jhead

Open Data Sets

2012-04-20T03:21:43+00:00

If you are evaluating reporting or analytics tools, or just like to mess about with them, it’s always good to get your hands on some “real world” data sets. It sure beats using the Steel Wheels, Classic Models, eFashion etc. sample databases typically shipped with the products.

For a truly comprehensive list of free data sets, check out this page on Quora. Below are some of my favourites:

Data.gov (US Federal Government data)
the Data Hub
Get the Data
Quality Web Data

The following sites are also worth following on a more ongoing basis:

Datablog on the Guardian
/r/opendata on Reddit

Install Oracle XE on Ubuntu

2012-02-04T11:21:13+00:00

Steps to install Oracle Express Edition (XE) database 10g on Ubuntu 11.10 (Oneiric).

Download the Oracle XE deb package (free registration is required).
Double click the downloaded file and select to install it.
In terminal run sudo /etc/init.d/oracle-xe configure.
You will be prompted to enter the following parameters: HTTP port number, database listener port number, SYSTEM and SYS database accounts password and whether the service should be started upon boot.
Thereafter the configuration might take a few minutes. That’s it. To start the service in the future run sudo /etc/init.d/oracle-xe start and to stop sudo /etc/init.d/oracle-xe stop.

Column-wise text manipulation

2011-10-17T17:02:14+00:00

GNU/Linux includes many utilities for working with text files through the shell. In this post we take a quick look at accessing and manipulating text files in a “column-wise” mode.

Suppose you have the following two files, each with two columns separated by the TAB character.

$ cat file1
Alice   Paris
Bob     Tokyo
Mary    London
John    New York

$ cat file2
13 May    Orange
19 Oct    Blue
11 Nov    Black
29 Feb    Red

The data in the two files are in fact related, i.e. file2 contains the date of birth and favourite colour of the people mentioned in file1 (assuming also that the files are sorted correctly). It would make sense to combine the two files together so that each row has the full data for each person. The paste command does just that.

$ paste file1 file2 > file3
$ cat file3
Alice   Paris     13 May    Orange
Bob     Tokyo     19 Oct    Blue
Mary    London    11 Nov    Black
John    New York  29 Feb    Red

Suppose that we are only interested in the name and date of birth of each person, and we can discard the hometown and favourite colour information. The cut command is what we shall use:

$ cut file3 -f 1,3 > file4
$ cat file4
Alice   13 May
Bob     19 Oct
Mary    11 Nov
John    29 Feb

Our next and final requirement is to reorder the columns differently. Instead of having the name followed by date of birth, suppose we want to have the columns the other way round. Unfortunately cat -f 3,1 produces exactly the same output as cut -f 1,3, so the cut command will not be sufficient. We have to use sed instead.

$ sed -e 's/\([^\t]*\)\t\([^\t]*\)/\2\t\1/' file4 > file5
$ cat file5
13 May    Alice
19 Oct    Bob
11 Nov    Mary
29 Feb    John

How does that work? Well $[^\t]*$ is a “named expression” which matches all characters except TAB. The search pattern looks for two of them, separated by TAB (\t). In the replace-with part, they are referred to as \2 and \1, again separated by \t.

Of course if file5 was what we ultimately wanted from the beginning as our output, we could have simply piped commands together:

$ paste file1 file2 | cut -f 1,3 | sed -e 's/\([^\t]*\)\t\([^\t]*\)/\2\t\1/' > file5

or alternatively

$ paste file1 file2 | sed -e 's/\([^\t]*\)\t\([^\t]*\)\t\([^\t]*\)\t\([^\t]*\)/\3\t\1/' > file5

Remove HTML tags with sed

2011-10-17T12:16:13+00:00

Sed can be used to strip out all HTML or XML tags from a file and get the plain text version. Suppose you have file gnulinux.html with the following contents:

<p>The combination of <a href=“/gnu/linux-and-gnu.html“>GNU and Linux</a> is the <strong>GNU/Linux operating system</strong>, now used by millions and sometimes incorrectly called simply “Linux“.</p>

Tempting but incorrect - sed finds the longest possible match which in this case is the entire file, and thus will output nothing:

$ sed -e 's/<.*>//g' gnulinux.html

Correct version:

$ sed -e 's/<[^>]*>//g' gnulinux.html
The combination of GNU and Linux is the GNU/Linux operating system, now used by millions and sometimes incorrectly called simply “Linux“.

TrueCrypt tray icon in Unity

2011-08-16T02:16:35+00:00

If you use TrueCrypt under Ubuntu 11.04 Natty you would have noticed an annoying behaviour. Under previous versions an icon is present in the system tray which remains there whilst a volume is mounted even if the TrueCrypt window is closed. Under Unity the tray icon is not shown. If you accidentally close the window (instead of minimizing it), there’s no easy way of getting back to it. Launching TrueCrypt again results in a error message.

The fix as suggested on shocm.com is to set the systray-whitelist property by running the following through command line (you will need to restart afterwards):

gsettings set com.canonical.Unity.Panel systray-whitelist "['all']"

However, your mileage may vary, and on my netbook this did not fix the issue. It seemed like the icon was placed in the tray, but it was rendered as a very thin strip about 1-2 pixels wide which could not be clicked.

The only way I found of getting out of missing window scenario was to resort to using TrueCrypt through the command line to dismount all mounted volumes.

truecrypt /d

This will also exist TrueCrypt and afterwards it can be launched as usual.

Script to get Report Viewer servlet mapping

2011-08-11T02:32:27+00:00

Sometimes it may be useful to know inside the report which servlet mapping is used to run the report (e.g. frameset, run, preview).

var sMapping = reportContext.getHttpServletRequest.getRequestURI();
var nPos = sMapping.lastIndexOf( "/" ) + 1;
this.text = sMapping.substring( nPos );

You can place the above code inside a label to see the servlet mapping.

BIRT 3.7 Released

2011-06-28T14:03:48+00:00

BIRT 3.7, previously codenamed Indigo, was released on June 22. Here are the necessary links to find out more about this latest version:

Generic code to get BIRT report parameters dynamically (new and improved!)

2011-06-09T16:57:31+00:00

In an earlier post we discussed a generic way to dynamically get the list of report parameters at run time without having to hardcode the parameter names in the script. As was correctly pointed out in the comments, the code did not work for parameter groups (and also cascading parameters). However, it is possible to modify the code to get it working even for those cases, and the change is not a huge one.

The main difference is we will use the method getAllParameters() instead of getParameters() of ReportDesignHandle. It seems that getParameters returns only the “top level” parameters, whereas getAllParameters flattens the groups and the nested as well as top level parameters. One thing to watch out for is that the return types of the two functions are different: java.util.List (getAllParameters) vs. org.eclipse.birt.report.model.api.SlotHandle (getParameters). Also, we have included a check for the class of the parameter entry in the list, in order to exclude the groups themselves. You can comment out the if statement in case you wish to see the group names as well.

Here is the updated working code:

var sOutput = "";
var parameterArray = reportContext.getDesignHandle().getAllParameters();
var parameterCount = parameterArray.size();
for( var i = 0; i < parameterCount; i++ )
{
  var sParClass = parameterArray.get( i ).getClass().toString();
  if( sParClass == "class org.eclipse.birt.report.model.api.ScalarParameterHandle" )
  {
    var sParName = parameterArray.get( i ).getFullName();
    var sParVal = reportContext.getParameterValue( sParName );
    sOutput = sOutput + sParName + " = " + sParVal + "\n";
  }
}
this.content = sOutput;

Working with the Palette in BIRT charts, Part 1

2011-06-03T14:31:45+00:00

On this blog we have often talked about overriding the default behaviour of the BIRT chart palette by dynamically setting colours based on data values. However, it is perhaps worth looking in more detail at the palette itself to understand the default behaviour and appreciate how it can be tweaked.

Each chart has a palette. The palette determines the colours used for drawing the series in the chart. From the UI perspective, the palette options are accessed on the last tab of the Edit Chart dialog (Format Chart), the first selection in the tree on left-hand-side (Series). It is worth noting that a chart only has one palette, even if the chart contains multiple series.

By default there are 32 entries in the palette. They are used in the chart from top to bottom, i.e. in the default scenario the first category will be coloured blue, the next one red and so on. The Add and Remove buttons in the Series Palette dialog can be used to change the number of entries. What happens when the chart contains more categories than the list of palette entries? The answer is that the palette will wrap around, i.e. the 33rd category will be coloured in the same way as the first one. If the number of categories is known in advance, one can extend the palette using the Add button to create the necessary number of palette entries. (Naturally, one should question the design of such a chart, will the user really be able to extract any meaning from a chart with 32 or more different colours? In most cases, probably not.)

Each palette entry itself can be edited. Not only is it possible to set one of the predefined colours, one can also set a custom colour, a linear gradient based on two colours or even an image file. It is also possible to specify different colour for positive and negative values.

As we already mentioned, the palette colours are applied top to bottom without any further logic, in particular they are not tied to the actual data point values themselves. Several common scenarios and scripting approaches for solving the issue have already been discussed on this blog: Setting BIRT chart series palette dynamically, Setting BIRT chart series palette dynamically, part 2 – area charts, Setting BIRT chart series palette dynamically, part 3 – stacked bar charts.

In the second part of this article we will look at how the palette and related objects can be manipulated programmatically, i.e. through scripting.

Removing description from Firefox bookmarks

2011-04-18T12:59:14+00:00

By default Firefox populates the Description field of a bookmark with the content of the page’s <meta name="Description" content="..." /> tag. I find is a little annoying and was looking for a way to remove these descriptions.

Since I have a lot of bookmarks I wanted to clean them all up in one go rather than editing them one by one. Luckily there is an easy way to do this since Firefox stores the bookmarks in an SQLite database file which can be opened and manipulated.

Install SQLite Database Browser (Ubuntu: sudo apt-get install sqlitebrowser Windows: download and install from SourceForge).
IMPORTANT! Export your Firefox bookmarks to have a backup in case something goes wrong.
Close Firefox (you can’t edit the bookmarks file while Firefox is running).
Run SQLite Database Browser and open the places.sqlite file which is located in your profile folder.
Run the following SQL which will remove the description from all bookmarks.
```
delete from moz_items_annos where anno_attribute_id = 2
```
Save and close, run Firefox.

Reference on the places.sqlite file can be found on mozillaZine and Mozilla Developer Network.

Remove Mono from Ubuntu

2010-12-29T00:49:49+00:00

After finally getting some time to fully read up on Mono (especially on the excellent The Source) I have decided it is best to remove it from my system. The Open Sourcerer has a nicely written up set of instructions for 10.04 Lucid Lynx and 10.10 Maverick Meerkat.

Open source BI: BIRT vs Jasper vs Pentaho

2010-12-29T00:33:58+00:00

In case you missed these, Innovent Solutions (one of the corporate backers of Eclipse BIRT project) published papers comparing Jasper and Pentaho to BIRT. Naturally, they conclude that BIRT is top of the pile in open source reporting, however they do justify this conclusion and the papers make an interesting read.

Generic code to get BIRT report parameters dynamically

2010-11-18T14:42:00+00:00

UPDATE: For an improved version of the code which works correctly with parameter groups and cascading parameters please see this updated post. Thank you to Stork for pointing out the problem with this code.

The traditional way of accessing BIRT report parameters from script is through the expression ReportContext.getParameterValue( parameterName ). Naturally this method requires one to know the name of the parameter at design time (i.e. when writing the script), which is fine in most cases.

There are however situations in which a more generic approach is preferable. For example, one might wish to implement a usage statistics system, where each time a report is run certain information is persisted in a usage tracking database. This will include the name of the report, the time of execution and perhaps also the selected parameter values. The obvious difficulty is that different reports are likely to have different sets of parameters. In anything but the simplest and smallest set of reports, it would be impractical to edit the code individually for each report. On the contrary, the appropriate approach is to create a generic library component which can be maintained in one place and referenced from the reports.

The code below is a simple demonstration how the list of parameters and their values can be read dynamically at run-time. To see it working, simply paste it into the onPrepare method of a text element.

var sOutput = "";
var parameterArray = reportContext.getDesignHandle().getParameters();
var paramaterCount = parameterArray.getCount();
for( var i = 0; i < paramaterCount; i++ )
{
  var sParName = parameterArray.get( i ).getFullName();
  var sParVal = reportContext.getParameterValue( sParName );
  sOutput = sOutput + sParName + " = " + sParVal + "\n";
}
this.content = sOutput;

Retrieve BIRT report name in script

2010-11-18T14:33:02+00:00

The following expression will dynamically get the file name of the report:

reportContext.getReportRunnable().getReportName();

Two points to note:

The expression actually returns the full report URI rather than just the name, i.e. something like file:/C:/BIRT/Report01.rptdesign.
The URI is percent-encoded and so space characters will be returned as %20 and so on for other special characters, e.g. file:/C:/Program%20Files/Apache%20Software%20Foundation/Tomcat%205.5/webapps/birt-viewer/Report01.rptdesign.

Remove empty lines from file

2010-09-22T16:50:07+00:00

Here’s a quick way to remove empty lines from a file using the Linux command line:

cat file1 | sed /^$/d > file2

Where file1 is the input file containing empty lines and file2 is a newly created file with empty lines removed.

Setting BIRT chart series palette dynamically, part 3 – stacked bar charts

2010-09-09T13:09:49+00:00

In what is rapidly becoming a mini-series, we have so far discussed how to set BIRT chart palette dynamically (based on category values) for pie charts and area charts. Today we cover stacked bar charts, i.e. bar charts with the Optional Grouping data element.

Once again, let’s start with a quick recap. In what is a fairly common scenario, one chooses the palette colours to match with particular category values. For example, in the chart below “High” is represented in green, “Mid” in orange and “Low” in red.

However, if for a particular dataset one of the of category values is not present, the palette colours are still used in the same order, meaning the “Mid” area is now shown as red and “High” as orange. This is confusing for the end user:

As in the previous examples, we solve this problem by adding a little bit of script to override the chart’s default behaviour.

function beforeDrawDataPoint( dph, fill, icsc )
{
  var sValue = dph.getSeriesDisplayValue();
  // set( R, G, B, alpha )
  if( sValue == "1-Low" )
  {
    fill.set( 242, 88, 106, 255 );
  }
  else if( sValue == "2-Mid" )
  {
    fill.set( 232, 172, 57, 255 );
  }
  else if( sValue == "3-High" )
  {
    fill.set( 128, 255, 128, 255 );
  }
}

We also need to override the beforeDrawLegendItem method, so that colours in the legend match the chart colours.

function beforeDrawLegendItem( lerh, bounds, icsc )
{
  var sValue = lerh.getLabel().getCaption().getValue();
  var fill = lerh.getFill();
  // set( R, G, B, alpha )
  if( sValue == "1-Low" )
  {
    fill.set( 242, 88, 106, 255 );
  }
  else if( sValue == "2-Mid" )
  {
    fill.set( 232, 172, 57, 255 );
  }
  else if( sValue == "3-High" )
  {
    fill.set( 128, 255, 128, 255 );
  }
}

The palette colours are now assigned dynamically based on actual category values. The rendered chart looks as shown below, independent of the colours selected in Chart Wizard and their order.

Selectively hiding series labels in BIRT area chart

2010-09-09T12:43:49+00:00

Series labels can be shown in BIRT area charts by opening the Chart Wizard and navigating to the Format Chart tab, then selecting Series > Value (Y) Series > Show Series Labels checkbox. The result will look as shown in the screenshot below:

Often there is one particular grouping (series) which is especially important and we want to draw the report viewer’s attention to it by showing the labels for that series only. This cannot be achieved through the Chart Wizard UI but can be done with a bit of scripting.

The method which needs to be overriden is beforeDrawSeries. In this example, series labels will be shown for the “1-Low” series and hidden for the other ones.

function beforeDrawSeries( series, isr, icsc )
{
  // get class of the renderer
  var type = isr.getClass().toString();
  // check for area chart renderer
  if( type == "class org.eclipse.birt.chart.render.Area" )
  {
    var val = isr.getSeriesRenderingHints().getDataPoints()[0].getSeriesDisplayValue();
    if( val == "1-Low" )
    {
      series.getLabel().setVisible( true );
    }
    else
    {
      series.getLabel().setVisible( false );
    }
  }
}

The result looks as follows:

How to change SSH port number on Ubuntu server

2010-09-03T08:56:48+00:00

Changing the port number of SSH daemon is a quick way of reducing the number of SSH brute force attacks your server might face (check the file /var/log/auth.log to see if there are many failed SSH login attempts).

Just to be on the safe side, create a backup copy of the SSH daemon config file.
```
sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.vanilla
```
Edit the config file.
```
sudo vi /etc/ssh/sshd_config
```
Change the port number on the following line, e.g. to 2201 or some other unused port. Make sure you note down the port number.
```
Port 22
```
Restart the SSH daemon. You might get kicked out of your existing session.
```
sudo /etc/init.d/ssh restart
```
When you login next remember to include the correct port.
```
ssh youruser@yourserver -p 2201
```

Disable Update Manager pop-up in Ubuntu

2010-08-07T05:56:20+00:00

Here’s how to disable the annoying Update Manager pop-up (technically a “pop-under”) and instead have the update icon displayed in the notification area.

Hit Alt-F2 to open the “Run Application” dialog.
Type in gconf-editor to run the GNOME Configuration Editor.
Navigate to Apps > Update Notifier.
Untick the auto_launch checkbox.

Thunderbird: Notifications and Indicator Applet in Ubuntu Lucid

2010-08-05T14:59:53+00:00

This post is an update on integrating Thunderbird with Ubuntu’s notification system. For Ubuntu 10.04 Lucid Lynx it supersedes my earlier post on the topic which was applicable previous versions of Ubuntu (Jaunty and Karmic).

The big difference in Lucid Lynx is the Indicator Applet and the “Me Menu”, both of these incorporating features related to the “social from the start” marketing tagline. In particular, the Indicator Applet integrates with Evolution, Ubuntu’s default mail client, to show new email notifications and allow quick access to the mail client. Once again, no out-of-the-box integration with Thunderbird. So the challenge is twofold: integrate with the notification mechanism (black pop-ups) as well as the Indicator Applet. The Mail Notification extension unfortunately falls short in the latter part.

Luckily, Ruben Verweij has developed libnotify-mozilla, a Thunderbird extension which works just great for both of the above requirements. Be sure to check out the blog (here and here) and the project’s Launchpad page to get the details and latest news. Here are the steps to set up the extension:

Download the Mozilla Notifications Extensions .xpi file and save it in a temporary location on your system.
Open Thunderbird and install the extension (Tools > Add-ons > Install).
Disable the native Thunderbird notifications by unticking “When messages arrive: Show an alert” in Edit > Preferences.
Install libnotify-bin package (execute in Terminal):
```
sudo apt-get install libnotify-bin
```
In order to have Thunderbird entry in the menu even when it is not running. First create a new file as follows (run from Terminal):
```
mkdir -p ~/.config/indicators/messages/applications
gksudo gedit ~/.config/indicators/messages/applications/thunderbird
```
Then paste the following text in the file and save it:
```
/usr/share/applications/thunderbird.desktop
```
(optional) If you wish you can remove the Evolution entries from the indicator menu. Note: because of bug 533021, this is a workaround which will remove Evolution from the menu for all users on the system, not just yourself.
```
mkdir -p ~/.config/indicators/messages/applications-blacklist
sudo mv /usr/share/indicators/messages/applications/evolution ~/.config/indicators/messages/applications-blacklist
```
(Once the above bug is resolved in the future, move the file back to its original location and create a softlink to it from the blacklist directory: ln -s /usr/share/indicators/messages/applications/evolution ~/.config/indicators/messages/applications-blacklist/evolution)
Log out from your user session and back in.

Keeping track of scripts in BIRT reports

2010-08-03T14:21:38+00:00

The ability to add custom scripts to report elements is a very powerful feature of BIRT. It allows the report developer to modify or override the default behaviour of the element; this blog features many examples of when this might be useful. However, as the number of scripts in a report increases, the report becomes harder and harder to maintain.

The Layout view or the Property Editor window do not indicate whether and what scripts exist on a particular element, and so it would seem the only way to check is to select the element and switch to the Script tab and look through the methods. Of course this would be incredibly tedious and impractical in a complex report.

Luckily, the Outline fast view has a Scripts item tucked away at the bottom of the list. When expanded, this shows all items in the report which contain custom scripts (expanding the item shows the overridden methods). Right-click brings up an option to go to the report element in the report Layout, and thus actually figure out which item it is referring to.

The deeper lesson is that one should use scripts only when necessary and if there is no other way to implement the required functionality. And of course thorough documentation also helps with maintenance…

Alternate row styling for summary rows

2010-08-02T13:14:37+00:00

The technique for alternate row styling described in a previous post is applicable for tables with detail rows (a detail row in a table corresponds to a row in the bound data set). However, it is often the case that the table does not contain any detail rows at all and instead displays only aggregated data, i.e. header or footer rows of a group.

In such scenario the row.__rownum value cannot be used, because __rownum is incremented for each row in the data set, meaning its value will depend on how many rows are being aggregated into the summary row.

Instead, the highlight logic can be defined using a variable incremented on each summary row.

First, initialize the variable. This can be done e.g. in the onCreate method of a label in the static column header.
```
reportContext.setPersistentGlobalVariable( "aggRowNum", "0" );
```
In an object on the summary row (either a label, aggreation or the row itself) the following code is placed in the onCreate method to increment the value of the variable (the funny stuff is to force explicit conversion between string and number and back):
```
var n = reportContext.getPersistentGlobalVariable( "aggRowNum" );
n = (n*1) + 1;
reportContext.setPersistentGlobalVariable( "aggRowNum", "" + n );
```

Finally, the highlight property of the row is set as follows:

reportContext.getPersistentGlobalVariable( "aggRowNum" ) % 2; | equal to | 1

Managing Passwords with KeePass and KeePassX

2010-07-31T04:07:33+00:00

Password proliferation is a serious problem on the web today. Most websites require users to register and create a username/password combination for future authentication. Unfortunately not many websites support reusable logins such as OpenID.

The main problem is that of human memory. It is of course not reasonable to expect the user to remember 100+ unique passwords. In most cases, the end result is that users will reuse the same password for multiple sites and systems. The issues with this are obvious: if a malicious third party gets hold of one password, it compromises all where the password was used; also, by piecing together the other bits of data entered at registration (such as date of birth, gender, physical address, mother’s maiden name etc.) for different sites, the attacker might be able to create a very accurate profile which could then be used to gain access to even those systems where a different password was used.

That’s why I use a password management program, in particular KeePass/KeePassX. It allows one to securely store credentials and is itself protected by strong encryption and can only be accessed using a password. In reality one finds that on a daily basis it is sufficient to remember 5-10 most frequently used passwords (computer login, email, Google, social network, internet banking and of course the password manager itself) and the rest can be referred to from KeePass. The program has a feature to generate random passwords, which is ideal to have strong passwords for infrequently accessed systems where one might not even realise the account was hacked for a long period of time. KeePass can even be installed in portable mode, which means you can carry the program and your encrypted passwords file on a USB stick.

I found that KeePass (version 1 for Windows) and KeePassX (Linux and Mac) suit my needs perfectly. There is also a version for Android and iPhone (refer to the Wikipedia article). Best of all? It’s free software licensed under GPL.

VMware Player in Lucid Lynx

2010-05-19T14:42:07+00:00

As always after a kernel update, VMware Player 2.5.xx asks to be recompiled after upgrading to Ubuntu 10.04 (Lucid). However during the compilation I got errors about virtual network device, even after trying to recompile several times including from command line.

After struggling for some time, I thought I would check on the VMware website whether there is a new version of the software; and indeed VMware Player is now in version 3. After installing it (by downloading and running the .bundle file) everything works fine in Lucid. As a side note, the compilation dialogue does not come up and the look and feel of the Player is also quite different.

Disable cookies in Thunderbird

2010-05-15T08:35:02+00:00

Recently I discovered that by default Thunderbird accepts cookies from web content (version 3.0.4 in Ubuntu 10.04 Lucid). I am a bit baffled by what would be a valid use case for storing cookies in an email client, and so here are steps for disabling this option.

Edit > Preferences.
Select Security icon and “Web Content” tab.
Untick “Accept cookies from sites”.
While you’re there, also check “Show Cookies” and “Remove All Cookies” to get rid of whatever has been stored up until now.

Change date format in Thunderbird

2010-05-15T08:20:33+00:00

In order to show dates as yyyy-mm-dd instead of the default (for US locale) mm/dd/yyyy I use the following script to launch Thunderbird in Ubuntu (tested with Thunderbird 3.0.4 on Lucid):

#!/bin/sh
export LC_TIME=en_DK.utf8
[ "$LC_ALL" != "$LC_TIME" ] && unset LC_ALL
exec thunderbird "$@"

This handy tip comes from mozillaZine.

Thunderbird "Could not initialize the browser's security component"

2010-04-11T12:53:40+00:00

UPDATE: The issue has been fixed in a subsequent Ubuntu system update, so there should be no reason to go through the steps below if your system is up-to-date.

After a recent system update in Ubuntu 9.10 (Karmic) I started getting an error message in Thunderbird starting with “Could not initialize the browser’s security component”. Among other things, this means that Hotmail integration with Thunderbird no longer works.

The error dialog itself has a few suggestions, however none of these fixes the issue.

Luckily the solution can be found on Ubuntu forums and is very straightforward. All that is required is to remove the package “libnss3-0d”. This can be achieved from Synaptic (System > Administration > Synaptic Package Manager) or from the command line:

sudo apt-get remove libnss3-0d

Here is the link to the original post on Ubuntu forums and the corresponding bug on Launchpad.

Export Outlook contacts as vCard

2010-03-30T16:23:27+00:00

Microsoft Outlook allows saving of contact in vCard format (vcf) only one at a time through the Save As… dialog. The Import and Export menu options do not provide the ability to export all contacts as vCard. Obviously with a large address book it would be very impractical to go through the contacts and save them one by one. Luckily it’s not too difficult to script this functionality through a macro. The quick-and-dirty macro below does just that. Note that the script considers the “current” folder, i.e. you need to be in the Contacts folder you want to export when executing the macro.

Sub save_as_vcf()
  Dim i, ncount As Integer
  Dim fullname As String
  Set ofolder = Application.ActiveExplorer.CurrentFolder
  Set oitems = ofolder.Items
  ncount = oitems.Count
  MsgBox "Count is " & ncount
  For i = 1 To ncount
    Set oitem = oitems.Item(i)
    fullname = oitem.fullname
    oitem.SaveAs "D:Export" & fullname & ".vcf", olVCard
  Next
  MsgBox "Done"
End Sub

Reading cookies in BIRT

2010-03-01T13:29:15+00:00

It is fairly straightforward to read a value stored in a cookie. This can have many uses, for example if the landing page for your reporting application needs to pass some values to your reports but you don’t want them visible in the URL.

The code sample below retrieves the value of a cookie and stores it in a global variable. The code could be placed in one of the startup methods, such as the report’s initialize.

// name of the cookie to read var cookiename = "birtcookie"; // variable to hold cookie value var cookieval = ""; // get the value from the cookie var request = reportContext.getHttpServletRequest(); var cookies = request.getCookies(); for( var i = 0; i < cookies.length; i++ ) { if( cookies[i].getName().equals( cookiename ) ) { cookieval = cookies[i].getValue(); } } // store value in a global variable reportContext.setPersistentGlobalVariable( "cookieval", cookieval );

Setting BIRT chart series palette dynamically, part 2 – area charts

2010-02-18T14:08:23+00:00

In a previous post we described how to set the series palette dynamically for a pie chart. A slightly different approach is required for area charts.

Let’s recap on the problem at hand: in what is a fairly common scenario, one chooses the palette colours to match with particular category values. For example, in the chart below “High” is represented in green, “Mid” in orange and “Low” in red.

However, if for a particular dataset of the of category values is not present, the palette colours are still used in the same order, meaning the “Mid” area is now shown as red and “High” as orange. This is confusing for the end user.

Once again we can solve this issue with some scripting of the chart. In this approach, we will override the beforeDrawSeries method to check for category value and set the fill colour based on that:

function beforeDrawSeries( series, isr, icsc )
{
  // get class of the renderer
  var type = isr.getClass().toString();
  // check for area chart renderer
  if( type == "class org.eclipse.birt.chart.render.Area" )
  {
    // get global counter
    // 1* forces conversion to int
    var i = 1 * icsc.getExternalContext().getScriptable().getPersistentGlobalVariable( "seriesCounter" );
    // get category value
    var val = isr.getSeriesRenderingHints().getDataPoints()[0].getSeriesDisplayValue();
    // set fill colour based on category value
    if( val == "1-Low" )
    {
      isr.getSeriesDefinition().getSeriesPalette().getEntries()[i].set( 242, 88, 106, 128 );
    }
    else if( val == "2-Mid" )
    {
      isr.getSeriesDefinition().getSeriesPalette().getEntries()[i].set( 232, 172, 57, 128 );
    }
    else if( val == "3-High" )
    {
      isr.getSeriesDefinition().getSeriesPalette().getEntries()[i].set( 128, 255, 128, 128 );
    }
    // increment global counter
    i = i + 1;
    // "" forces conversion to string
    icsc.getExternalContext().getScriptable().setPersistentGlobalVariable( "seriesCounter", "" + i );
  }
}

You may have noticed that a global variable seriesCounter is used to hold the reference to the current series. This is because the beforeDrawSeries method is called several times, once for each category value present in the data. Another bit of code is therefore required to define the seriesCounter variable in the initialize method of the report:

reportContext.setPersistentGlobalVariable( "seriesCounter", "0" );

One more point to note is that reportContext.setPersistentGlobalVariable only accepts string values, hence the “hack” to convert between a number and a string every time the value is retrieved or stored.

Setting BIRT chart series palette dynamically

2010-01-13T18:05:03+00:00

BIRT series palette is static by default, meaning colours are applied in the specified order without being tied to the actual category values. This is ok in most cases, however consider the following scenario. In our data we expect three category values, “1-Low”, “2-Mid” and “3-High” and the chart series palette has been set to reflect this. Red colour is first in the list, so it will used for the first category value (“1-Low”) etc.:

With all three category values in the dataset everything works as expected:

However, suppose that for a particular dataset the value “1-Low” is not present (perhaps a month when the business is performing well?). In this case the palette colours will still be applied in the same order starting with red, leading to inconsistency and quite possibly confusing the users:

This problem can be overcome by dynamically scripting the series colours based on the category value. Two methods need to be scripted, one for the chart itself and the other for the legend (otherwise the chart and the legend will not match!).

function beforeDrawDataPoint( dph, fill, icsc )
{
    var sValue = dph.getBaseDisplayValue();
    if( sValue == "1-Low" )
    {
        fill.set( 242, 88, 106, 255 );
    }
    else if( sValue == "2-Mid" )
    {
        fill.set( 232, 172, 57, 255 );
    }
    else if( sValue == "3-High" )
    {
        fill.set( 128, 255, 128, 255 );
    }
}

function beforeDrawLegendItem( lerh, bounds, icsc )
{
    var sValue = lerh.getLabel().getCaption().getValue();
    var fill = lerh.getFill();
    if( sValue == "1-Low" )
    {
        fill.set( 242, 88, 106, 255 );
    }
    else if( sValue == "2-Mid" )
    {
        fill.set( 232, 172, 57, 255 );
    }
    else if( sValue == "3-High" )
    {
        fill.set( 128, 255, 128, 255 );
    }
}

The set method can take either three integer parameters with values between 0 and 255 for Red, Green, Blue or four integer parameters (RGB + Alpha channel for opacity). After including the above scripts the chart is generated with the correct colours for the category values:

Setting BIRT chart title dynamically

2010-01-13T12:55:10+00:00

It is possible to set the title of a chart dynamically, for example based on parameter values, using a little bit of scripting. The example below assumes that two parameters are defined (“Year” and “Month” with values such as “2010” and “Jan”).

function beforeGeneration( chart, icsc )
{
    var sYear 	= icsc.getExternalContext().getScriptable().getParameterValue( "Year" );
    var sMonth 	= icsc.getExternalContext().getScriptable().getParameterValue( "Month" );
    var sTitle	= "Chart for " + sMonth + " " + sYear;
    chart.getTitle().getLabel().getCaption().setValue( sTitle );
}

The title of the chart will be set dynamically based on report parameter values.

VMware Player mouse issues in Karmic

2010-01-12T13:43:12+00:00

VMware Player experiences mouse capture problems when run under Ubuntu 9.10 Karmic host. Inside the guest window, the mouse pointer works fine in a top-left rectangle of the window (640x480 pixels?) but outside of this area the mouse pointer switches its focus to the host. Add the following line to the file /etc/vmware/bootstrap to fix it:

export VMWARE_USE_SHIPPED_GTK=yes

Important note: VMware code needs to be recompiled each time the Linux kernel is updated and this entry may prevent it from compiling successfully. The additional line should be removed or commented out prior to building VMware Player and then put back in back again.

For a discussion see this thread on Ubuntu forums.

BIRT Report Viewer documentation

2010-01-11T14:15:26+00:00

Eclipse BIRT comes with Report Viewer, a J2EE application used for generating and displaying reports. Whilst deploying and using the out-of-the-box application on Tomcat is straightforward, there are fairly rich configuration and parametrization options which are non-obvious. The following two documents describe how the viewer works and how to control its behaviour.

BIRT Viewer User’s Guide (covers version 2.3, PDF)
Using the BIRT Report Viewer (covers version 2.2)

Change Firefox address bar search engine

2010-01-11T14:10:36+00:00

Follow these steps to change the search engine used by Firefox 3 address bar:

Enter about:config in the browser’s address bar and accept a warning dialog if it appears.
In the filter box type in keyword.URL
Double click the entry and paste in your prefered search engine URL (e.g. http://www.bing.com/search?q=)

You can always revert back to the default Google search by right-clicking the entry and selecting the Reset menu option.

Tuxradar: Command line tricks for smart geeks

2009-12-16T13:46:40+00:00

Good article on Tuxradar with some clever command line hacks: Command line tricks for smart geeks

Fill missing values in BIRT charts

2009-11-19T18:26:24+00:00

The BIRT chart wizard provides an option to skip missing values in a series and connect them with the series line; however, there is no option to substitute a default value for the missing data. The screenshot below shows a chart where the series value is missing for category value 03-MAR and the “Connect Missing Values” option has been selected under the value series options:

There is no option in the chart wizard to fill in the missing values, i.e. replace them with a default. However, it is possible to achieve this with a simple script. In this case we check for the series name and replace the missing values with 0. To use the script, highlight the chart in the UI and click the Script tab along the bottom of the main window. Then simply paste the script below and save the report.

function afterDataSetFilled( series, dataSet, icsc )
{
  if( series.getSeriesIdentifier() == "Series 1" )
  {
    var list = dataSet.getValues();
    for( var i = 0; i < list.length; i = i + 1 )
    {
      if( list[i] == null )
      {
        list[i] = 0;
      }
    }
  }
}

The screenshot below shows the chart with the script included:

Use commandline to find CentOS version

2009-11-18T17:58:42+00:00

Here’s how to find the version of your CentOS system from the command line:

more /etc/redhat-release

Ctrl-Alt-Backspace to restart X in Karmic

2009-11-07T05:43:55+00:00

In a previous post I described to how to enable the Ctrl-Alt-Backspace key combination to restart the X server. However, those steps were applicable to Ubuntu 9.04 only and have no effect in Ubuntu 9.10 (Karmic Koala). The necessary changes to enable Ctrl-Alt-Backspace to restart X in Karmic are below.

Open Preferences > Keyboard and select the Layouts tab.
Click the Layout Options… button.
In the dialog window expand the “Key sequence to kill X server” entry and select the checkbox.

Set screen to grayscale with Compiz

2009-10-23T16:00:07+00:00

Compiz sometimes gets bad press because of the gimmicky, bling nature of some of the plugins. Whilst it’s hard to see the real-world benefit of painting fire or rain drops on the screen, on the other hand it has to be said that Compiz gives Linux the wow factor that certain users are drawn to. And of course there is the odd practical thing one can achieve with it.

One of these which I have found after a bit of searching is a very simple and straightforward way of turning the screen into grayscale (or monochrome). You might ask why anyone would want to turn their screen into grayscale, and my answer is: it is a welcome respite for tired eyes, especially when working at night or in a dark environment.

To achieve this effect, you need to have Compiz itself installed, as well as the compizconfig-settings-manager package. This gives you an entry in System > Preferences called CompizConfig Settings Manager. One of the plugins available under the Accessibility section of the Settings Manager is “Color filter”. It comes with a set of predefined filter files one of which is grayscale. Key bindings are available for active window or the whole screen and for switching between the filters.

Depending on your preference, you can either cyclicaly switch to the grayscale filter or just remove the other filters. For reference, the default filter files including grayscale are kept in /usr/share/compiz/filters.

Open the 'Safely Remove Hardware' dialog manually

2009-10-05T14:13:53+00:00

Sometimes the Windows system tray icon used to safely remove USB hardware disappears. It is not a good idea to simply unplug the USB device, especially a memory stick or hard drive, since this can lead to data loss or corruption. Also, the disk will not be unmounted cleanly and you may face issues when trying to mount it later in Linux.

To open the dialog manually and remove the device cleanly, run the following command from the Windows Run dialog (Start > Run):

RUNDLL32.EXE SHELL32.DLL,Control_RunDLL HotPlug.dll

Change virtual terminal font size

2009-09-21T05:28:14+00:00

This post is about how to change the resolution (i.e. font size) of virtual terminals or “tty” in Linux. Virtual terminal is the basic command line interface which you see when you press <Ctrl><Alt><F1> (note: to get back to your existing Gnome or KDE session press <Alt><F7>). This is different from the Terminal emulator, such as the Terminal application in Gnome.

To change the font size of the virtual terminal it is necessary to set the vga parameter in the entry used by the Grub bootloader to start up Linux. Follow the steps below to set the entry correctly.

First, intall the hwinfo utility through Synaptic or Terminal:
```
sudo apt-get install hwinfo
```
Then run the following command in Terminal:
```
sudo hwinfo --framebuffer
```

The command will output some information about your graphics system. Skip the top bit and you should see a list of entries like this:

Mode 0x0300: 640x400 (+640), 8 bits
Mode 0x0301: 640x480 (+640), 8 bits
Mode 0x0303: 800x600 (+800), 8 bits
Mode 0x0305: 1024x768 (+1024), 8 bits
Mode 0x0307: 1280x1024 (+1280), 8 bits
Mode 0x0317: 1024x768 (+2048), 16 bits
Mode 0x0318: 1024x768 (+4096), 24 bits

Review the list which might be quite long, select the resolution you want to use and copy the hexadecimal number after Mode. For example, for 24 bit 1024x786 resolution the number is 0x0318.
Still in the Terminal emulator, run the following command to edit the Grub bootloader configuration file:
```
gksudo gedit /boot/grub/menu.lst
```
Find the entry you want to edit (or copy an existing entry and give it a different name) and change the line which begins with “kernel”. As a precaution, make sure you have at least one entry left in the file without the new resolution so you can still safely boot and edit the file again if necessary. Original entry:
```
kernel		/boot/vmlinuz-2.6.28-15-server root=/dev/sda3 ro quiet splash
```
New entry:
```
kernel		/boot/vmlinuz-2.6.28-15-server root=/dev/sda3 ro quiet vga=0x0318 splash
```
Reboot your computer and at the Grub menu select the entry which was edited. You may notice some difference during the boot process, to verify that the resolution and font size are suitable press <Ctrl><Alt><F8> once you are at the login screen. This will take you to tty8 which should display messages from the boot process.

Greasemonkey for beginners

2009-09-21T04:36:15+00:00

Tuxradar, a site worth keeping an eye on, published a basic Greasemonkey for beginners tutorial a little while back. Greasemonkey is a Firefox plugin which allows you to add little scripts which are executed when you browse to a particular page. The script can manipulate the page itself, e.g. to show additional content or to hide annoying ads or whitespace, change style and much much more. Many thousands of scripts have been published and if you know Javascript and browser scripting it’s very easy to created your own. Here’s a couple of other Greasemonkey links:

Greasemonkey for beginners (Tuxradar)
Greasespot
Dive Into Greasemonkey (the definite reference)
userscripts.org (a script repository)

Split large files

2009-09-18T14:33:20+00:00

Sometimes it is necessary to split a large file into several smaller ones, for example so that they fit on a CD or USB disk or can be attached to email. It’s very easy to do this from command line.

Suppose you have a file of 500 MiB called “large_file” and to split it into 5 files of 100 MiB each:

split --bytes=100m large_file large_file_part_

This will create 5 files with names as follows:

large_file_part_aa
large_file_part_ab
large_file_part_ac
large_file_part_ad
large_file_part_ae

The following command would then be used to join the parts back together:

cat large_file_part_* > large_file

JDBC drivers in BIRT Viewer on Tomcat

2009-08-31T14:54:15+00:00

JDBC drivers need to be put in the following location to be available in BIRT Viewer. Putting them into <TOMCAT HOME>/common/lib does not work in BIRT and you will get a “cannot load JDBC driver” error.

<TOMCAT HOME>/webapps/birt/WEB-INF/platform/plugins/org.eclipse.birt.report.data.oda.jdbc_2.3.1.v20080827/drivers

The Tomcat path and version number will depend on your environment.

Fix DOSBox keyboard mapping in Ubuntu

2009-08-01T04:59:39+00:00

If your keyboard doesn’t seem to be working correctly in DOSBox running on Ubuntu (for example, if arrow and page up keys don’t work), try the following:

Check if a file called .dosboxrc exists in your home directory, e.g. by running
```
more ~/.dosboxrc
```
Create or edit this file by running
```
gedit ~/.dosboxrc
```
Add the following text to the file and save:
```
[sdl]
usescancodes=false
```

Formatting chart legend value entry

2009-07-28T17:11:57+00:00

In the legend properties for BIRT meter charts (accessed via Format Chart > Chart Area > Legend) there is a Show Value checkbox which controls displaying the series value together with its name. For some reason, in the Entries the dialog the Format control appears to be disabled, and so there is no way to control the format of the value. This is especially a problem when the computed value contains a lot of decimal places, as shown below:

My solution to get around this problem is to add a little bit of script to the chart. Simply paste the following code to the charts onRender event (select the chart, click the Script tab at the bottom of the main editor window, select onRender in the first dropdown and beforeDrawLegendItem in the second one):

function beforeDrawLegendItem( lerh, bounds, icsc )
{
    var nVal = lerh.getValueLabel().getCaption().getValue();
    nVal = Math.round( nVal ) + "%";
    lerh.getValueLabel().getCaption().setValue( nVal );
}

The result is a nicely formatted percentage value:

Reducing wasted whitespace in meter charts

2009-07-28T15:50:09+00:00

BIRT has a wonderful meter chart type which is very useful for building KPI-based performance dashboards. However, it can be a little tricky to get the visual layout of the chart right. With default settings most of the chart is empty blank space with a relatively small dial in the middle. This is because the meter (dial) appears to be taking only a small portion of the overall area and also the distances between the chart title, legend and the dial are too big. This can look disjointed in a dashboard-style report. See the screenshot below, which shows a meter chart with a legend below and otherwise default settings. The background colour is set to blue to highlight the amount of empty space wasted:

The trick to make the dial take up a larger portion of the overall chart area is to set a couple of “inset” entries to negative values. The values below worked well for me for a chart with width of 4.5 in and height 3 in.

To move the legend closer to the meter, go to Format Chart > Chart Area > Legend > Layout and set Insets (points) > Top to -20. This assumes that the legend Position is set to Below.
To move the dial closer to the title, go to Format Chart > Chart Area > Plot > Area Format and set Insets (points) > Top to -30.

The screenshot below shows the same chart with the above two changes:

The exact values may need some trial and error playing around to get the layout exactly right, but the general principle is: don’t be afraid of setting negative inset values.

Start Eclipse without splash image

2009-07-21T13:33:48+00:00

Recently it’s happened a few times that the splash image, normally only shown while Eclipse is being loaded, remains visible even after Eclipse is fully loaded (using Eclipse 3.2.2 on Ubuntu 9.04). Even though it is only a minor annoyance since the splash can be closed from the Window List (aka task bar), I prefer no to show the splash image at all. This can be achieved by editing the file /usr/lib/eclipse/eclipse.ini and adding -nosplash on top.

Fixing Eclipse BIRT PermGen space errors on Ubuntu

2009-07-18T05:08:33+00:00

Unfortunately the default memory settings for Eclipse are not sufficient to run BIRT properly on Ubuntu. Editing BIRT reports was fine on my machine, but the preview always crashed or froze Eclipse. When run from the command line, errors like these came up:

Exception in thread "SocketListener0-0" java.lang.OutOfMemoryError: PermGen space
Exception in thread "SocketListener0-1" java.lang.OutOfMemoryError: PermGen space
Exception in thread "SocketListener0-2" java.lang.OutOfMemoryError: PermGen space
java.lang.OutOfMemoryError: PermGen space

Googling for these errors reveals that it is sadly a common problem with Eclipse. The fix is to increase the memory available to the Java process. This can be done in three different ways: Passing vmargs parameters from command line (not practical), editing the /usr/lib/eclipse/eclipse.ini file (did not work for me) or setting the parameters in the user’s eclipserc file (see below).

After some trial and error and more googling, the third option is what I went for:

Close Eclipse if it is running.
Check whether the following file already exists: ~/.eclipse/eclipserc
If yes, skip to step 4. However, it looks like a bug that this file is not created by default and moreover there is no sample in Ubuntu install. To get the vanilla file, copy and paste it from this post on Ubuntu forums and save it in the above location.
Open the file and change this line
```
VMARGS="-Xmx256M"
```
to something like
```
VMARGS="-Xmx256M -XX:PermSize=256M -XX:MaxPermSize=512M"
```
These values worked fine for me but you may have to tweak them.
Save the file and start Eclipse. You should now be able to run preview of BIRT reports.

BIRT chart scrollbars in Firefox

2009-07-15T15:27:55+00:00

There’s a strange bug in BIRT charting with Firefox on Linux. Some charts are rendered with horizontal and vertical scrollbars, sort of like an embedded frame which is too big to fit in the allocated space.

The fix for this annoyance is straightforward, simply change the output format from SVG to PNG on the first tab of the chart dialog. This also makes scrolling smoother and improves overall responsiveness of Firefox when a report with a lot of charts is displayed.

Installing Apache Tomcat on Ubuntu server

2009-06-23T16:33:49+00:00

Here’s how to install Apache Tomcat version 5.5 on an Ubuntu machine (note that there is nothing Ubutu specific in these steps). This will form one of the foundation steps for a series of posts in which we will build a fully open-source business intelligence platform.

First, install Java JDK. I am using Sun’s version mainly for stability and to avoid any compatibility issues.
```
sudo apt-get install sun-java6-jdk
```

Download Apache Tomcat and check for integrity.

wget http://mirrors.sirium.net/pub/apache/tomcat/tomcat-5/v5.5.27/bin/apache-tomcat-5.5.27.tar.gz
wget http://mirrors.sirium.net/pub/apache/tomcat/tomcat-5/v5.5.27/bin/apache-tomcat-5.5.27.tar.gz.md5
md5sum -c apache-tomcat-5.5.27.tar.gz.md5

Unpack the archive file.
```
tar xvzf apache-tomcat-5.5.27.tar.gz
```
Move the unpacked directory to its permanent location. I use /opt but this is only a personal preference.
```
sudo mv apache-tomcat-5.5.27 /opt
```

Create a simple startup and shutdown script. Run sudo vi /etc/init.d/tomcat and save it with the following content:

#!/bin/bash
# Tomcat startup script

export JAVA_HOME=/usr/lib/jvm/java-6-sun

case $1 in
start)
	sh /opt/apache-tomcat-5.5.27/bin/startup.sh
;;
stop)
	sh /opt/apache-tomcat-5.5.27/bin/shutdown.sh
;;
restart)
	sh /opt/apache-tomcat-5.5.27/bin/shutdown.sh
	sh /opt/apache-tomcat-5.5.27/bin/startup.sh
;;
*)
	echo "Usage: /etc/init.d/tomcat {start|stop|restart}"
	exit 1
;;
esac
exit 0

Don’t forget to make this script executable.
```
sudo chmod 755 /etc/init.d/tomcat
```
Now we can finally start Tomcat.
```
/etc/init.d/tomcat start
```
Finally, check that everything worked correctly by opening the Tomcat default page (http://<servername>:8080) in a web browser.

DOSBox mount C drive at startup

2009-06-17T14:53:19+00:00

Here’s a tip to save typing the mount command each time you start DOSBox. Simply create a file called .dosboxrc in your home directory and save it with the following content:

[autoexec]
MOUNT C ~/OldApps
c:

Where ~/OldApps is the directory with MS-DOS executables. Here’s a how-to with more information about DOSBox under Linux.

Goodbye WebMail, hello POP

2009-06-10T15:52:21+00:00

For a long time the only way to access and use a Hotmail account from Thunderbird was the WebMail extension. All in all, this is a great solution but it always seemed a bit of a workaround since in the background it “pretends” to be a browser, downloads the Hotmail HTML and parses it to get and send emails.

This has recently changed since the Hotmail team has come to its senses and now once again allows POP3 and SMTP access to the service. This means it is now straightforward to configure Thunderbird to use Hotmail, and no extensions are required.

As summarized by poster vtel57 on Google Groups:

incoming server: pop3.live.com - port 995 - SSL outgoing server: smtp.live.com - port 587 - TLS Be sure that Secure Password Authentication is NOT checked. Works like a champ! :)

Indeed it does, and we will even forgive vtel57 the use of a smiley.

One more thing to note is that once configured to use POP, Thunderbird will download the entire contents of your Hotmail inbox. So it is a good idea to do a bit of a clean up by deleting old items or moving them to an archive folder.

Setting simple table borders in BIRT

2009-06-07T16:18:13+00:00

Here’s how to create simple uniform table borders in BIRT. This seems very obvious once you know how to do it, but messing around again and again with cell and row borders without getting the right result can be very frustrating!

Hover over the table to get the “Table” handle in the bottom left corner.
Click on the “Table” handle to get the row / column handles.
Click on the top-left corner and this will select the whole table (although in the Properties window you will see “Cell”!).
Now set the desired border setting in the Properties window and they will be applied uniformly (Excel style) on all cells in the table.

Mount NTFS disk from commandline

2009-06-07T15:56:09+00:00

Nautilus and Thunar sometimes refuse to mount NTFS disk (e.g. a USB hard drive) when it was previously not unmounted cleanly from Windows. It is still possible to mount it from terminal shell by using the following command:

sudo mount -t ntfs-3g -o force /dev/sdc1 /media/myntfsdisk

Where /dev/sdc1 is the device you want to mount and /media/myntfsdisk is the mount point.

Full Circle

2009-06-03T02:37:05+00:00

Full Circle is a free online monthly magazine covering all things Ubuntu. Featuring tips, interviews, reviews and opinions, it’s worth checking out.

Check installed packages from commandline

2009-05-28T13:31:24+00:00

To check for installed packages from the command line, use the dpkg command with the --get-selections option. This returns all packages installed on your system (most likely a lot!). So it is best to use grep to narrow down the search results. For example, the following command lists all packages with “fire” in the package name:

dpkg --get-selections | grep fire
firefox                        install
firefox-3.0                    install
firefox-3.0-branding           install
firefox-3.0-dom-inspector      install
firefox-dom-inspector          install
mozilla-firefox-locale-en-gb   install

An alternative which shows more information, including the exact version of the package and a description is the -l option. Because grep works with the output of the dpkg command, this will also include packages where the search term appears in the description, such as ufw on the last line in the output below because of “firewall”.

$ dpkg -l | grep fire
ii firefox                         3.0.10+nobinonly-0ubuntu0.9.04.1              meta package for the popular mozilla web bro
ii firefox-3.0                     3.0.10+nobinonly-0ubuntu0.9.04.1              safe and easy web browser from Mozilla
ii firefox-3.0-branding            3.0.10+nobinonly-0ubuntu0.9.04.1              Package that ships the firefox branding
ii firefox-3.0-dom-inspector       3.0.10+nobinonly-0ubuntu0.9.04.1              dummy upgrade package for firefox-3.0-dom-in
ii firefox-dom-inspector           3.0.10+nobinonly-0ubuntu0.9.04.1              meta package for firefox-dom-inspector
ii mozilla-firefox-locale-en-gb    2.0.0.7+1-0ubuntu4              Mozilla Firefox English language/region pack
ii ufw                             0.27-0ubuntu2              program for managing a netfilter firewall

Using the above commands can be a faster and more efficient alternative to searching for installed packages in Synaptic.

Stop system beep in VMware Player

2009-05-25T13:41:52+00:00

Here’s how to stop the annoying beep (system bell) in VMware Player. These steps were tested with VMware Player 2.5 running a Debian Lenny server (guest) under Windows XP Professional (host).

Open the following file in Notepad: C:\Documents and Settings\<your user>\Application Data\VMware\preferences.ini (the drive might be different depending on your setup).
Add the following line at the end and save:
```
mks.noBeep = "TRUE"
```
Open the virtual machine’s VMX configuration file in Notepad.
Add the following line (same as above) at the end and save:
```
mks.noBeep = "TRUE"
```
Launch VMware Player and run the virtual machine - the beep should be gone!

Jaunty notifications in Thunderbird and Firefox

2009-05-23T17:45:08+00:00

One of the major new features in Ubuntu 9.04 (Jaunty) has of course been the new notification system. For what it’s worth, I think it’s a pretty good, bold piece of work and the notifications look pretty good. The trouble is, as with any new framework, that not all applications out there are using the new notifications, leaving the overall impression somewhat disjointed. Good news is that with a bit of tweaking Firefox and Thunderbird can be made to send their messages to the notification area.

Firefox: Credit for this tip to the OMG! Ubuntu blog: For Firefox, there is an add-on (currently experimental) which sends the “Download complete” messages to the notification area. You should also change the browser.download.manager.showAlertOnComplete setting to false under about:config to stop Firefox’s native little notification from popping up.

Thunderbird: For Thunderbird’s “New email” notification, I found that the GNOME Mail Notification applet works very well. Follow these steps to set it up:

First install Mail Notification by running
```
sudo apt-get install mail-notification
```
Once installed, open the Mail Notification config dialog from System > Preferences > Mail Notification.
On the first tab (General) click the Add button and browse to the Inbox file of the Thunderbird mail account for which you want to display notifications. The Inbox file should be under location similar to this one :
```
/home/<your user>/.mozilla-thunderbird/<random code>.default/Mail/<your account>/Inbox
```
(.mozilla-thunderbird is a hidden directory in your home directory).
Make sure that on the last tab (Message Popups) the “Enable message popups” check box is ticked.
Now configure Mail Notification to run on session start up: open System > Preferences > Startup Applications and click Add. Name and Description can be set to anything, under command enter
```
mail-notification --sm-disable
```
Last step is to open Thunderbird and disable its native notification messages by going to Edit > Preferences and on the General tab uncheck “Show an alert”.

All going well you should now have Thunderbird using the new notifications and a cool applet in your notification area showing you if there are any unread messages in your Inbox.

LinuxLinks: 20 of the Best Free Linux Books

2009-05-20T13:22:18+00:00

I recently came across an article on LinuxLinks with links to a selection of 20 of the Best Free Linux Books available for download. Worth checking out.

Remove OC4J auto-startup after installing OBIEE

2009-05-19T15:29:54+00:00

Installing Oracle BI Enterprise Edition (OBIEE) will by default also install the OC4J application server. On Windows machines, it is not installed as a service, instead it runs in a dedicated command shell window. By default, OC4J will start automatically at the session startup, not only bringing up the annoying command line window but also slowing down your system. There is no setting in the installer to prevent this.

To prevent the automatic startup, open Registry Editor and remove the value “oc4j” under the key HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun.

There is also a way to make OC4J into a Windows service, although I haven’t tried this myself.

Tracker: corrupted index, high CPU

2009-05-17T14:04:30+00:00

My only issue after an otherwise smooth upgrade to Ubuntu 9.04 (Jaunty) has been with Tracker. After logging in I noticed high disk and CPU usage, and eventually an error came up regarding corrupted index. I have tried several times to re-index, this did not work; also pausing all indexing in the tracker applet has no effect on the CPU usage by the trackerd process.

The error and solution are discussed in more detail on Ubuntu Forums. The following suggestion fixed the problem for me:

sudo apt-get install tracker-utils
tracker-processes -r

And then letting tracker rebuild the index at the start of next session. Note that the above command will remove all existing tracker files (this should not be a problem since they’re causing the issue in the first place) and that depending on how much data needs to be indexed it can take a while to recreate the index.

BADSIG error in Ubuntu Update Manager

2009-05-14T15:56:29+00:00

Here are a few things you can try if you get the BADSIG error in Update Manager:

Run the following commands from terminal shell:

sudo apt-get clean
sudo apt-get update -o Acquire::http::No-Cache=True

Change the Ubuntu server from which updates are downloaded: System > Software Sources > Ubuntu Software tab > change the selected server in the “Download from” dropdown.

Resize and rotate images in Nautilus

2009-05-14T12:57:16+00:00

nautilus-image-converter is a helpful package which adds two entries to the Nautilus context menu for resizing and rotating images. It works for selections of multiple images, too, and has options for creating copies or editing the images in place.

To install from command line:

sudo apt-get install nautilus-image-converter

Mount an ISO CD-ROM image in Windows

2009-05-10T15:00:49+00:00

In a half-unofficial way, Microsoft offers a driver and a small utility to mount ISO CD-ROM images as a drive in Windows XP and Vista. It can be downloaded from a posting on Microsoft support site (here is the link directly to the self-extracting archive). The instructions are included in the “readme.txt” file. Although the program comes without any support from Microsoft it seemed to work fine for me.

Prompt for variables in Oracle SQL*Plus

2009-05-09T10:02:31+00:00

To prompt the user for a value when running SQL statements in SQL*Plus use the & symbol. The query below will prompt for variable “name” twice:

select 'Hello ' || '&name' from dual
union all
select 'Goodbye ' || '&name' from dual;

To prompt for any given variable only once and use the entered value multiple times use two ampersands instead of one. The query below will prompt for the variable “name” once only:

select 'Hello ' || '&&name' from dual
union all
select 'Goodbye ' || '&&name' from dual;

To prevent prompting altogeher, use the set define command:

set define off
select 'Hello world & dog' from dual;

A few useful grep examples

2009-05-06T13:41:23+00:00

There is a simple tutorial on Ars Technica’s Open Ended site with several useful examples of the grep command. Further examples can be found in the comments section.

Convert DICOM images to JPEG

2009-05-06T13:27:27+00:00

Medical images, e.g. X-Rays, are commonly stored in the DICOM format. By default you won’t be able to open these in Ubuntu, but there is actually a package in the repositories which lets you convert DICOM image files to more common formats, e.g. JPEG, PNG or bitmap.

sudo apt-get install dcmtk
dcmj2pnm +oj img00000 img00000.jpg

The above commands will install the dcmtk package and take a DICOM image img00000 and convert it to lossy JPEG image img00000.jpg. The dcmj2pnm command also supports other output formats, e.g. PNG. To print the help text simply run

dcmj2pnm -h

There are other commands in the dcmtk package, e.g. dcmcjpeg which provides a lot of JPEG encoding options.

Lightweight Xubuntu

2009-05-04T12:59:19+00:00

The latest issue of DistroWatch Weekly has a feature on reducing the memory footprint of Xubuntu 9.04. This is in response to an earlier comparison of performance and memory consumption between Xubuntu and Debian with Xfce, published in the previous edition of DistroWatch Weekly.

Unfortunately the sequence of steps starts by installing a minimal Ubuntu setup with command line only and then adding to it bit by bit, meaning a reinstall. I would also like to see the steps of simplifying a full blown Xubuntu setup by removing unnecessary components.

As an aside, I am typing this post on a fairly old laptop with only 256 MB RAM running Xubuntu 9.04 (Jaunty), and I have to say that for light everyday use (ie. Firefox, Thunar, Terminal, Mousepad) it is absolutely fine. I have been toying with the idea of installing Zenwalk or Debian (with Xfce of course!), we’ll see.

Problems with USB memory stick in Xubuntu 9.04

2009-05-02T06:59:49+00:00

After upgrading from Xubuntu 8.04 (Hardy) to 9.04 (Jaunty), the automount feature stopped working for a particular USB memory stick. It wasn’t even listed when I ran commands like

sudo fdisk -l

and

more /proc/partitions

But interestingly, when I plugged in my camera via a USB cable, the memory card inside it was automounted, and even the troublesome USB stick was then recognized and mounted!

The solution turned out to be manually updating the initramfs image of the new kernel 2.6.28-11 installed as part of the Jaunty upgrade. After running the command below and rebooting the machine, the USB stick is now recognized and automounted immediately after inserting it.

sudo update-initramfs -u -k `uname -r`

Note the backward quotes in the above command.

Login as someone else

2009-04-30T16:03:38+00:00

Sometimes you may want to log in with a different user account in Terminal without logging out from your X session or switching to an unused virtual console. There are two different approaches to do this in Ubuntu: interestingly, it is possible without even knowing the other user’s password.

Approach 1: if you know the password of the other account (<username> is replaced with the account you want to log in as, e.g. bob or pinky or whatever):

su -l <username>

Approach 2: if you don’t know their password. This only works if you have administrative privileges, i.e. your account is in the sudoers file. The password you are prompted for is your own one:

sudo -i -u <username>

or even execute the command from our approach 1 with sudo:

sudo sh -c 'su -l <username>'

Note: It goes without saying that you should behave responsibly and not abuse this to gain access to other user’s data.

Two quick changes in Firefox about:config

2009-04-29T12:41:54+00:00

Here are two quick and simple changes which I always make on a fresh Firefox install. They are both accessed through the about:config URI. Simply type about:config to the Firefox address bar and accept the disclaimer. This reveals a lot of “hidden” settings which cannot be changed directly through the preferences dialogs.

To make backspace button go back in history (this is default in Windows but not in Linux), change the value of browser.backspace_action to 0.
To open the result of search from the search bar in a new tab change the value of browser.search.openintab to true.

A reference of these and other about:config parameters can be found in the MozillaZine Knowledge Base.

BIRT: Prevent text wrapping

2009-04-29T12:34:31+00:00

The property which controls text wrapping (line breaks) in table cells and other objects in BIRT is accessed in the Properties Editor window under Properties > Advanced > Text > Whitespace. Simply set the value to “No Wrapping” and the contents of the cell will be displayed on a single line.

Disable laptop touchpad tapping in Xubuntu 9.04

2009-04-27T16:00:43+00:00

In a previous post I detailed steps on how to disable touchpad tapping in Xubuntu 8.04. Unfortunately the package gsynaptics-mcs-plugin which provides the Xfce Settings Manager plugin is obsolete in Xubuntu 9.04 (Jaunty) and therefore the annoyance of touchpad tapping and scrolling is back after upgrading from Hardy. Also, it turns out that the responsibility of managing input devices has been moved from the X server to HAL (Hardware Abstraction Layer) and so different steps are required in Xubuntu 9.04 / Xfce 4.6:

Confirm that HAL is aware of the touchpad by running:
```
lshal | grep synaptics
```
The command should produce output similar to this
```
input.x11_driver = 'synaptics'  (string)
```
Run the following command to create a new file to enable the SHMConfig option in HAL
```
sudo mousepad /etc/hal/fdi/policy/shmconfig.fdi
```

Paste the following into the file and save:

<?xml version="1.0" encoding="ISO-8859-1"?>
<deviceinfo version="0.2">
  <device>
    <match key="input.x11_driver" string="synaptics">
      <merge key="input.x11_options.SHMConfig" type="string">True</merge>
    </match>
  </device>
</deviceinfo>

Reboot your machine.
Run the following command to verify that HAL has picked up the setting
```
lshal | grep x11_options
```
It should produce output like this
```
   input.x11_options.SHMConfig = 'True'  (string)
```
Run the following command
```
synclient TouchpadOff=2
```
Verify that touchpad tapping and scrolling are now disabled.
The same command has to be run at the startup of each session. To do this, go to Applications > Settings > Session and Startup and on the Application Autostart tab add a new entry. Name and Description can be set to whatever, Command is the same as above:
```
synclient TouchpadOff=2
```

Versions

2009-04-25T06:56:23+00:00

Here are a few useful commands for finding version information of various system components.

Linux distribution name and version
```
lsb_release -idrc
```
System information, including kernel version
```
uname -a
```
X.org version
```
X -version
```
Java version
```
java -version
```
Package version
```
dpkg -s <insert package name>
```

Enable Ctrl-Alt-Backspace to restart X

2009-04-25T06:15:28+00:00

UPDATE: These steps work fine for Ubuntu 9.04 (Jaunty). For more recent Ubuntu versions you should take a look at this later post which has the correct steps.

The Ctrl-Alt-Backspace key combination which restarts X is by default disabled in X version 1.6 (and hence in Ubuntu 9.04). Follow the steps below to re-enable it.

IMPORTANT Make a backup of your xorg.conf file. Note: messing up this file is not a good idea, so make a backup and be careful with it.
```
cd /etc/X11
sudo cp xorg.conf xorg.conf.backup
```
Open xorg.conf for editing (substitute gedit for mousepad if you are on Ubuntu)
```
sudo mousepad /etc/X11/xorg.conf
```

Add the following section at the bottom of the file:

Section "ServerFlags"
Option    "DontZap"    "no"
EndSection

Save the file, log out and back in. You can try the Ctrl-Alt-Backspase combination at the login window to make sure it works as expected.

Mount an ISO CD-ROM image

2009-04-24T04:14:02+00:00

Most CD-ROM downloads come as ISO images which can be burned onto a CD. They can also be mounted as drives without actually burning them onto a disk by using the mount loopback command. The command below mounts the image foobar.iso in user’s home directory as /media/cdrom:

sudo mount -o loop ~/foobar.iso /media/cdrom

This assumes that a /media/cdrom directory exists on you system (it does on Ubuntu). However, it’s easy enough to use a different directory, e.g.

cd ~
mkdir foobar
sudo mount -o loop foobar.iso foobar

The command to unmount is also straightforward

sudo unmount /media/cdrom

Fix Wine's Browse C: Drive

2009-04-23T14:22:00+00:00

Wine adds a menu entry “Browse C: Drive” in the Applications menu. By default, this doesn’t work and produces an error message in Xubuntu 8.04. Here’s how to fix it.

Run the following command to open the configuration file which controls what the menu entry does:
```
sudo mousepad /usr/share/applications/wine-browsedrive.desktop
```

Replace the line

Exec=xdg-open ~/.wine/drive_c

with the line

Exec=xdg-open $HOME/.wine/drive_c

Save, log out and back in (or Ctrl-Alt-Backspace to restart X) and the menu should now open the drive_c directory in Thunar.

And what is the unfamiliar xdg-open command, one might ask? According to its man page, it opens a URL (file, http, ftp) in the user’s preferred application. But apparently it does not recognize the ~ shorthand for the current user’s home directory.

Alternate row styling in BIRT

2009-04-22T12:57:56+00:00

Update: The technique documented in this post is applicable for alternating styles of detail rows. For a way of achieving the effect in a table consisting of summary rows only, please refer to this later post.

To set different styles for alternate table detail rows in BIRT:

Select the detail row - hover over the table, then click the table button which appears in the bottom left corner and finally click the row handle on the left hand side. The Property Editor window
In Property Editor go to the Highlights tab (last horizontal tab) and click Add. This will open the Highlight Rule dialog.
Enter the following condition (use 0 for styling the even rows or 1 for odd rows)
```
row.__rownum % 2 | Equal to | 0
```
Now set the styling you want, for example different background colour, and finally click OK to close the dialog window.

Change Oracle XE web ports

2009-04-21T13:48:56+00:00

Oracle Database XE (Express Edition, sometimes also referred to as Apex) comes with an embedded web interface for administration. By default the HTTP port of this web interface is 8080. This can be checked by running the query below when logged in as system:

SQL> select dbms_xdb.gethttpport from dual;

In order to change the port number, run the following SQL (the port is changed to 8181 in the example below) and restart the database:

SQL> begin
dbms_xdb.sethttpport('8181');
end;
/

If you want to disable the HTTP access altogether, you can set the port number to 0.

There are also similar methods dbms_xdb.getftpport and dbms_xdb.setftpport, although I am not sure in what context FTP is used with Oracle XE. By default the port is 0, i.e. disabled.

This incident will be reported

2009-04-21T01:23:12+00:00

My recent misadventures with adding a group membership for my user and in the process managing to remove all other groups (including admin) got me thinking about the message “... is not in the sudoers file. This incident will be reported.” Exactly where and how and to whom is this reported?

Well, according to clever people on linuxquestions.org, the log file where unsuccessful sudo attempts are logged (as well as other things related to authentication) is /var/log/auth.log. The command below will show you just those entries for unsucessful sudo attempts:

grep "user NOT in sudoers" /var/log/auth.log

Note also that a new file is created once the log reaches a certain size, and older files are archived. So if you need to check properly you will also want to look into the archived files (listing from my old Xubuntu laptop shown below):

ls -l /var/log/auth.log*
-rw-r----- 1 syslog adm  2319 2009-04-20 21:38 /var/log/auth.log
-rw-r----- 1 syslog adm 68936 2009-04-20 06:33 /var/log/auth.log.0
-rw-r----- 1 syslog adm  3697 2009-04-13 06:17 /var/log/auth.log.1.gz
-rw-r----- 1 syslog adm  1182 2009-04-04 10:17 /var/log/auth.log.2.gz
-rw-r----- 1 syslog adm  2088 2009-03-26 19:04 /var/log/auth.log.3.gz

Commands for Gnome Power Manager and Network Manager

2009-04-20T12:48:12+00:00

Every now and then the Power Manager and/or Network Manager applets crash and disappear from the notification area on my old Xubuntu 8.04 laptop. There have been some bugs posted about this on Launchpad, and it seems as if it should be fixed in more recent releases. Leaving that aside, here are the commands to run the two applets from command line.

Gnome Network Manager applet:

nm-applet &

Gnome Power Manager:

gnome-power-manager

or alternatively (this one will also open the preferences dialog):

gnome-power-preferences

Securing SSH

2009-04-20T02:35:02+00:00

This article on The Register has a link to a very good page on CentOS website with tips on securing OpenSSH. The tips are applicable for all distros, not just CentOS, and are definitely worth going through and implementing if you have SSH enabled on your server.

Good luck and stay secure.

Add user to group with usermod

2009-04-18T10:12:30+00:00

Here is a very simple one which caught me out: you want to add your user to a group through command line. The command is very straightforward:

sudo usermod -aG tools hammer

This adds the user “hammer” to the group “tools”. Notice the -a switch (for add). This means “hammer” will become member of “tools” and keep his exiting group memberships. However, if you run the command without the -a switch:

sudo usermod -G tools hammer

Then “hammer” becomes member of “tools” (all well and good) but has lost its other group associations defined previously - including on Ubuntu the group “admin”. So that next time you log in (you need to log out and back in for the group memberships to be reflected properly) and try to run sudo something you get a nice message like so:

hammer is not in the sudoers file. This incident will be reported.

Luckily, I had another user with admin priviledges on the machine and so was able to add all the groups which I removed by mistake. In any case, I will now remember to include the -a option next time I run usermod to add user to a group!

Greasemonkey script to get book ISBN number using GM_xmlhttpRequest

2009-04-17T19:21:52+00:00

A bit of background: for a while now I have been buying books from the SF Masterworks series from Orion Publishing, mainly when I am in a bookshop and I see a book from the series which I don’t yet have. So far I have bought sixteen of the books, and I though it would be nice to have the whole series (perhaps they will be considered collectable one day, who knows). Having spoken to my local bookshop, it turn out they would happy to order the rest of the series for me if I supply them with the books’ ISBN numbers.

Now, the SF Masterworks series page has a nice table with the books titles and authors as well as links to a more detailed page for each book. The table on the page can be nicely copied and pasted into a spreadsheet (Google Docs in my case) but the problem is that the ISBN numbers are not displayed on this over page, but on each book’s detailed page. Rather then having to click and copy & paste 70 times, I thought this would be a good opportunity to play with the GM_xmlhttpRequest functionality in Greasemonkey.

The script is uploaded on userscripts.org (together with a few of my other scripts), although being targetted for a one-off job I don’t think it will become a hit!

So, what are the learnings from this little exercice?

At a high level, the logic being the script is something along the lines:

Loop through the table
On each row get the link to the detailed page
Get the page via GM_xmlhttpRequest
Process the page to get the ISBN number
Display the ISBN number on the master page

Naively, I fell into the trap of calling GM_xmlhttpRequest from a for loop. This doesn’t work because GM_xmlhttpRequest works in an asynchronous fashion, meaning that the rest of the code will not wait for it to finish.

I then read up quite a bit on the related topic of closures and scope in JavaScript and ultimately decided that whilst it’s a very interesting topic, for getting things done I needed an quicker and (for me ) an easier solution.

The way I decided to go was good old recursion (“you can’t understand recursion unless you understand recursion”). So an array of links to the detailed pages is built up first, then we iterate over them - but rather than having GM_xmlhttpRequest in the loop itself, I let its callback function increment the loop counter and call the next iteration. The counter and the array of links are global variables, to get around this tricky problem with closures.

As far as processing the results of GM_xmlhttpRequest, it is a bit of a letdown that they come as a text and it is not possible to use DOM (it can be done for XML with DOMParser but there is nothing in Greasemonkey for parsing HTML text). So to retrieve the value of the ISBN number from the detailed page it is back to plain old string search.

It’s probably not the cleanest solution out there, but given that the objective was to save some time and effort with manual copy & paste for a one-off job, it works great. Following the KISS principle, I try not over-engineer something which is ultimately throwaway. At the same time, I got to play with GM_xmlhttpRequest for the first time, so the learning bonus is still there.

Now it’s off to the shop to get those books ordered - happy reading!

Restore menu bar in Xubuntu Terminal

2009-04-17T12:11:31+00:00

To save a bit of space, you can remove the menu bar in Xubuntu Terminal (Edit > Preferences > Appearance > uncheck “Display menubar in new window”. Here are the steps to restore it later on (since you can’t access the Preferences dialog without the menu itself!).

Run the following command to open the terminal configuration file in Mousepad:
```
mousepad ~/.config/Terminal/terminalrc
```
Change the line MiscMenubarDefault=FALSE to MiscMenubarDefault=TRUE and save the file.
That’s it - restart your Terminal and marvel at the beauty of its menu bar.

Disable laptop touchpad tapping in Xubuntu

2009-04-17T12:03:53+00:00

UPDATE: These steps work fine for Xubuntu 8.04 (Hardy). For more recent Xubuntu versions you should take a look at this later post which has the correct steps.

One of the things I find very annoying is the default “tap to click” behaviour of laptop touchpads. Here are easy steps how to configure Xubuntu to stop the touchpad tapping. It will also let you configure other touchpad settings. It comes courtesy of the Xfce goodies project.

Install the gsynpatics plugin for Xubuntu Settings Manager
```
sudo apt-get install gsynaptics-mcs-plugin
```
IMPORTANT Make a backup of your xorg.conf file. Note: messing up this file is not a good idea, so make a backup and be careful with it.
```
cd /etc/X11
sudo cp xorg.conf xorg.conf.backup
```
Open xorg.conf (in vi or mousepad or whatever)
```
sudo mousepad xorg.conf
```
Look for a block starting with Section "InputDevice", with Identifier "Synaptics Touchpad" on second line and ending with EndSection.
In the above block (e.g. just above the EndSection line) add the following line:
```
Option		"SHMConfig"		"on"
```
Save the file xorg.conf
Restart X (Ctrl+Alt+Backspace)
In the Applications menu, go to Settings > Settings Manager. This opens the in the Xfce Settings Manager where you should see a new entry called “Synaptics settings”.
Open this and to disable tapping simply uncheck “Enable tapping” on the middle tab.

Good luck and happy Xubuntuing on your laptops.

Install RealPlayer as a Firefox plug-in in Xubuntu

2009-04-17T11:42:16+00:00

I used the following steps to install RealPlayer in order to listen to BBC Radio. Although I did this on Xubuntu 8.04, it should also work for Ubuntu and other distros.

Download and install RealPlayer for Linux from Real. I downloaded the deb package and installed it through gdebi.
My install path was now /opt/real/RealPlayer. Check that the following two files exist:
```
/opt/real/RealPlayer/mozilla/nphelix.so
/opt/real/RealPlayer/mozilla/nphelix.xpt
```
Copy those two files to the Firefox plugins directory (the code below should be a single line):
```
sudo cp /opt/real/RealPlayer/mozilla/nphelix.* /usr/lib/firefox-addons/plugins/
```
Restart Firefox. You can verify that Firefox has picked up the plugin under Tools > Add-ons > Plugins. It should say something along the lines of “Helix DNA Plugin: RealPlayer G2 Plug-In Compatible”.

Good luck and happy listening.