VirtualBox - Let Host-Only mode access the internet

In an earlier post I described networking modes in VirtualBox. Combining those modes you'll get some kind of swiss knife in realizing somehow exotic networking modes in your VMs.
What if you want your VM that is configured for Host-Only mode access the internet?
Port forwarding using NAT is an option. But for me that sounded to complicated. I had the following requirements:

1. The host should be able to access services like Apache or GlassFish on the guests (the virtual machine)
2. The guests should be able to access the outside world (intranet/internet)
3. The guests should be able to talk to each other using fixed IP adresses
4. The host should be able to talk to the guests using fixed IP adresses

A working solution for these requirements is described in this blog article.

Using symbolic links under Windows

Since Windows Vista it is possible to use symbolic links just like you know it under Linux/Unix systems.
Warning: You have to use the command line to use this tool ;-)
The syntax is as follows:

 mklink [[/d] | [/h] | [/j]] <Link> <Target>  

Most of the time I use it with the /d option. This lets the link point to a directory.

Fixing poor performance (lagging) on Samsung Galaxy Nexus GSM (i9250) phones

Woohoo, I can't believe it. My Galaxy Nexus phone is affected by a bug which causes the phone to slow down and to behave very laggy after a while. Some users reported this might happen when they uploaded or downloaded huge files (e.g. movies).
I can't tell whether huge files caused this problem on my Galaxy Nexus, but from one day to another the phone was reacting very slow. It was no longer usable for me. Typing a single character on the keyboard was a pain in the ass ...
I started to google around and found this posting on XDA which saved my phone's life ;-)
If you are experiencing the same behavior on your Galaxy Nexus you might consider following the steps there. But be careful not to HARD BRICK your phone, because your phone must have a special chipset.
My phone was produced in 08/2012 and really has the "suspicious" V3U00M chipset mentioned in the XDA posting. I checked it using the eMMC Brickbug Check app from the play store.
If your phone is not rooted you can't fix the problem. Either you root it now, or you send it to Samsung and let them repair/swap it. It's up to you.
The next thing to do was to run the LagFix (fstrim) free app or paid version. I now use the paid version, because it has a built in scheduler which runs fstrim every night.
The script mentioned in the posting isn't necessary if you use the paid version of LagFix.
After running the LagFix app my phone was reacting as fast as on the day I bought it and it remains fast until now.

Multi Line Table Cells in Vaadin 6

I had a hard time figuring out how to wrap content in a table cell using Vaadin 6.7.
Content in row headers can be forced to wrap using a simple "<br/>" tag in the string. Unfortunately it isn't that simple with non-header cells.
I found a working solution in this Vaadin forum post.
You simply have to create your own CSS stylesheet definition and add the following code to it:

 .v-table-cell-wrapper {   
  white-space: normal;   
 }  

Howto compress and uncompress a Java byte array using JDK Deflater/Inflater

If you ever came across the requirement to store binary data somewhere (e.g. filesystem or database) it might be handy to compress those data.
Besides the common ZIP algorithm Java offers the Deflater and Inflater classes that uses the ZLIB compression library. ZLIB is part of the PNG standard and not protected by any patents.
Here is a small code snippet which shows an utility class that offers two methods to compress and extract a Java byte array.

 package de.qu.compression.demo;  
   
 import java.io.ByteArrayOutputStream;  
 import java.io.File;  
 import java.io.FileInputStream;  
 import java.io.FileOutputStream;  
 import java.io.IOException;  
 import java.io.InputStream;  
 import java.util.List;  
 import java.util.Map;  
 import java.util.zip.DataFormatException;  
 import java.util.zip.Deflater;  
 import java.util.zip.Inflater;  
   
 public class CompressionUtils {  
  private static final Logger LOG = Logger.getLogger(CompressionUtils.class);  
    
    
  public static byte[] compress(byte[] data) throws IOException {  
   Deflater deflater = new Deflater();  
   deflater.setInput(data);  
   
   ByteArrayOutputStream outputStream = new ByteArrayOutputStream(data.length);   
       
   deflater.finish();  
   byte[] buffer = new byte[1024];   
   while (!deflater.finished()) {  
    int count = deflater.deflate(buffer); // returns the generated code... index  
    outputStream.write(buffer, 0, count);   
   }  
   outputStream.close();  
   byte[] output = outputStream.toByteArray();  
   
   deflater.end();

   LOG.debug("Original: " + data.length / 1024 + " Kb");  
   LOG.debug("Compressed: " + output.length / 1024 + " Kb");  
   return output;  
  }  
   
  public static byte[] decompress(byte[] data) throws IOException, DataFormatException {  
   Inflater inflater = new Inflater();   
   inflater.setInput(data);  
   
   ByteArrayOutputStream outputStream = new ByteArrayOutputStream(data.length);  
   byte[] buffer = new byte[1024];  
   while (!inflater.finished()) {  
    int count = inflater.inflate(buffer);  
    outputStream.write(buffer, 0, count);  
   }  
   outputStream.close();  
   byte[] output = outputStream.toByteArray();  
   
   inflater.end();
   
   LOG.debug("Original: " + data.length);  
   LOG.debug("Uncompressed: " + output.length);  
   return output;  
  }  
 }  
   

It is also possible to receive better compression results by calling the method setLevel of the Deflater class and specify the constant Deflater.BEST_COMPRESSION.

Howto install icinga with the new PHP based web interface on Ubuntu 12.04

I had a hard time finding good articles about how to install icinga with the new web based PHP interface on Ubuntu 12.04.
I didn't want to grab the sources and compile it. Not that I am not able to do that, but in my opinion it should be an easier way to install it. We are living in 2013 and not in the last century ...
Anyway, to make a long story short I found a very good step by step guide on askubuntu which worked for me exactly the way it was described.
Kudos!

Google Kontakte in Roundcube Webmail nutzen

Die Einbindung von Google Kontakten in das Adressbuch von Roundcube ist mittels eines Plugins problemlos möglich.
Diese Anleitung beschreibt das Verfahren genau und ausführlich. Der dort aufgeführte Link auf die Zend GData API funktioniert aber nicht mehr.
Ich habe die aktuelle Version (1.12.1) von dieser URL heruntergeladen. Damit funktioniert es einwandfrei.

Permission problems with BackupPC?

If you encounter permission problems when using BackupPC check out this bug report and the solution in comment #15. It works.

Pure-FTP Daemon unter Ubuntu Linux installieren und konfigurieren

Und noch eine Perle der Installationsdokumentationen zum Aufsetzen eines FTP Servers (hier Pure FTP unter Ubuntu/Debian). Unter diesem Link findet sich eine schnelle und wie ich finde gut geschriebene, verständliche Anleitung zum Aufsetzen eines FTP Servers.

Mailserver für einen Homeserver unter Linux einrichten

Wer schon immer mal einen Mailserver auf seinem eigenen Server zu Hause betreiben möchte (Stichwort DynDNS), der sollte sich mal diese wirklich gute Anleitung durchlesen.
Die dort beschriebenen Komponenten

• Postfix
• Dovecot
• Fetchmail
• Sieve

harmonieren sehr gut zusammen.
Generell ist das komplette Wiki dort sehr gut aufgebaut und enthält einige sehr nützliche und tolle Anleitungen.