I couldn't believe it, but the whole java web start and stuff around it is just messed up on Linux platform. First, I tried to develop simple Hello world application and it worked OK. Great, I said to myself, but when I wanted to force JWS into some serious cooperation with serious 'Hello World 2' application, I encountered many problems there. First - JWS under Linux has really poor tools. I mean, yes, they work, but don't expect such a comfort as you have on MS Windows platform. No detailed information about errors if they are any. JWS simply won't run and when I want to have some feedback, I have to run my Windows XP box and run JWS app from there to find out what's going on. Second - Jar signing. When you want to do something serious, you will certainly want to sign your .jar files with your deployed application. So I bundled all my application's .jar files and .jar libraries into one .jar archive (BTW. see JPackItJPackIt which does this and it does really good job, but unfortunately has issues with JWS...this is another story) and I wanted to sign this .jar. OK, let's Google how to do that... keytool -genkey -keystore mykeystore {create keystore} jarsigner -keystore mykeystore mindtermfull.jar mykey {sign jar} That's nice and easy, however I encountered very wild errors on my Linux box and I'm still not able to fix them. keytool error: gnu.javax.crypto.keyring.MalformedKeyringException: MAC verification failed If anybody has experience in signing .jars on Linux, please share you knowledge in comments. On MS Windows XP box, it went smoothly and now I have my .jar signed and can keep moving... OS used: Debian Lenny and MS Windows XP EN Professional JDK 6 with latest updates on both platforms #### Part 2 - some good news Niklas Mehner made some good points in comments to this post, that led me into right direction. I discovered that Java has more solid ground in Linux than I thought. First, JWS has many settings I didn't know about and you can access it by simple command "javaws -viewer". Second, I thought I'm using 1.6 sun jdk, but there was still GJC stuck in my system and that was why I encountered such errors. Now everything works like a charm and commands that I wrote before are working too. Next time I will try to look at problems I encounter more deeply before blaming innocent pieces of SW in blog posts ...