Non-broadcast Wireless Networks with Microsoft Windows

When configuring the network ensure that the ‘Connect even if the network is not broadcasting’ option is checked. Can’t believe that I never thought of trying that – seems so obvious in hindsight!

Try the following to diagnose and resolve the problem….

Find Tomcat’s process id:

ps -ef | grep tomcat

Now kill the Tomcat process using the -3 flag (SIGQUIT signal) to force a thread dump:

kill -3 tomcat process id number goes here

Once the process has stopped take a look at the tomcat log file. You should see some thread dumps which will help to identify the application and code that is hanging on to threads.

java.lang.ClassNotFoundException: org.apache.commons.net.ftp.FTPClientConfig

The simple fix is to make sure Ant can find the Apache commons-net Jar, either from under the Ant lib directory or in a custom location.

I installed Ant using Aptitude which places all of the shared Ant jars in /usr/share/ant/lib. I was confused because there was a symbolic link to ant-commons-net.jar which I thought should contain the missing classes. Turns out this Jar is actually the Ant FTP task library, you still need to download the commons-net Jar file.

The answer is – Rarely! Or at least only in exceptional circumstances…..

The -9 signal is the KILL signal which forces a process to immediately terminate. Many processes perform clean up operations when they terminate, perhaps to close open files, remove temporary files & directories etc. Using the -9 signal prevents a process from executing any of its shut down hooks and could potentially leave your application / system in an inconsistent state.

If a process needs to be killed, it’s often better to use the kill command on its own or use kill -15 (-15 is usually the default signal) which sends the TERM signal to the process. The TERM signal tells a process to gracefully terminate which means it will be able to run any shut down hooks and thus leave your system in a potentially nicer state than it would have been if you’d have used kill -9.

I see kill -9 used in so many inappropriate circumstances, such as in scripts to stop some service or application. Kill -9 should never be used in such cases.

The *nix man pages have a good overview of the kill command. You can also get a list of all kill signals by executing kill -l.

I upgraded Ubuntu to 9.10 and found that all of my video content was being displayed with many of the colours totally messed up – pink sky and green skins on people!

For some reason the Hue graphics setting was set to -1000. To fix it, I corrected the setting via the graphics preferences in the Totem media player and everything looked fine afterwards.

I found the simple solution was to start Firefox via the profile manager which prevented the message from showing up again. To start Firefox from the profile manager simply execute the command below and choose your default browsing profile.

firefox -profilemanager

It’s quite simple to do. Just ensure you pass the following JVM argument when launching the application…..

-Dcom.sun.management.jmxremote

Start JConsole and you should get the option of connecting the the application you launched from Eclipse.

java.lang.NoClassDefFoundError: javax/transaction/Synchronization

For some reason I didn’t seem to have jta.jar (required library for Hibernate), so I added it manually to the CF lib directory and everything started working properly.

Wonder if anyone else has had this problem???

http://yokohead.com/2009/02/installing-java-x64-in-ubuntu-810/

From the command line execute (In windows use set instead of export):

export JAVAWS_VM_ARGS="-Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=y"

In Eclipse, configure a new debug configuration by choosing menu options Run -> Debug Configurations. Find the ‘Remote Java Application’ section, right click and choose ‘New’.

Change the port number to whatever you specified when setting up the JAVAWS_VM_ARGS environment variable. Click the apply button and close the window.

Now start your application:

javaws http://hostname:port/yourjnlpfile.jnlp

You can now attach the Eclipse debugger to the process by running the debug configuration you just set up. Set some breakpoints in your code and you should find the application suspends at the relevant points where you can debug the application as per normal.