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I used the Ubuntu (12.04) Software-Center to install IcedTea Web Control Panel and IcedTea Java Web Start to start a WebStart java-file with the ending jnlp. After this is done I tried to start a file from within firefox - I was able to select Open with IcedTea Java Web Start (default) from the pull down menu.

This did not work (unknown error occurred) with the suggestion to download the file and start is then. I did so, and after I found out that the command for Java Web Start is javaws I tied with that - just to find out it is not installed (or not in the search path).

I do not know how to continue, i.e. how to start this jnlp file from a terminal. Maybe I need to install something else? If so, what and how? Maybe I am confusing the different java 'things'? Maybe IceTea is no coffee? I am very unexperienced with java...

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I'm quite new to java too but here are some things you could try:

  • Check the Java alternatives config:

    In a terminal type: sudo update-alternatives --config java

    Icedtea is the open source implementation of javaws so I'd choose the java-6-openjdk-i386 option.

  • Check you have the correct plugin installed

    Make sure that icedtea6-plugin is installed

    (Not sure if it's strictly needed but it might be)

  • Check you have icedtea-netx installed

    I looked in the Software-Center at IcedTea Web Control Panel and IcedTea Java Web Start and in More Info both show at the bottom: version: icedtea-netx-common 1.2-2ubuntu1.3 However, there is also the package icedtea-netx which is what I installed on my system and icedtea-netx-common was installed automatically as a dependency.
    Using the Aptitude package manager I saw that:
    icedtea6-plugin Depends on icedtea-6-plugin and that
    icedtea-6-plugin depends on icedtea-netx

  • Make sure you are using javaws correctly.

    I use javaws to run the program 'Compass and Ruler C.a.R.' and the command looks like this:

    javaws -open %U -localfile -J-Djnlp.application.href= /home/jesse/.java/deployment/cache/6.0/31/7bca389f-718ab01a

    See man javaws for details about the command.

    You could also try installing C.a.R. from Start C.a.R. using Java Web Start to test if javaws is working. (I'm sure there is a simpler way to test it but I don't know what it is, sorry)

P.S. I find the Software-Center rather annoying because while it's visually very nice and great for finding new programs you might like to try, if you want to know the actual package name you have to click through to the More Info and check the version information at the bottom to discover what the actual package name is. (hint hint developers :-)

You can check whether a package in installed on your system by opening a terminal and typing: dpkg-query -l packagename e.g. dpkg-query -l icedtea* or dpkg-query -l *jdk*

You can then install the package by typing sudo apt-get install packagename pressing tab twice will also give you a list of possible options. e.g. type sudo apt-get install icedtea TAB TAB and you should get:

icedtea-6-jre-cacao  icedtea-7-jre-cacao  icedtea-netx-common
icedtea-6-jre-jamvm  icedtea-7-jre-jamvm  icedtea-plugin
icedtea-6-plugin     icedtea-7-plugin     
icedtea6-plugin      icedtea-netx
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