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    <p>If you just want to run some shutdown specific code, the "proper Java" way to handle this would not use signals, but would instead add a generic "shutdown hook" that would run when your application was about to terminate. This is one of those least-common-denominator problems that Java sometimes suffers from. (Since not all platforms support <code>SIGINT</code>, in Java, no platform supports <code>SIGINT</code>.)</p> <p>Unfortunately, you don't get much context in a <a href="http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/Runtime.html#addShutdownHook%28java.lang.Thread%29"><code>ShutdownHook</code></a>, but it may still be useful:</p> <pre><code>Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() { public void run() { // cleanup } })); </code></pre> <p>If you really need to distinguish between the signal received, or you want to support signals that Java normally ignores (like <code>USR1</code>), or you want to abort shutdown based on a signal, then a <code>ShutdownHook</code> will be mostly useless for you, unfortunately.</p> <p>There is a non-supported, poorly-documented way to capture signals in the Sun JVM, using the <code>sun.misc.SignalHandler</code> class. This is questionably portable, though it appears that the <a href="http://www.ibm.com/developerworks/ibm/library/i-signalhandling/">IBM JVM also supports this</a>.</p> <p>For example - you could hook up a signal handler to listen to <code>SIGHUP</code> reload your server configuration, which was set up in the <code>init.d</code> script as the <code>reload</code> verb:</p> <pre><code>Signal.handle(new Signal("HUP"), new SignalHandler() { public void handle(Signal signal) { reloadConfiguration(); } }); </code></pre> <p>As for configuring a Java application to be controlled using the <code>system</code> command, you should write a shell script in <code>init.d</code> program that starts it up. This simply needs to respond to the <code>start</code> and <code>stop</code> verbs and take the appopriate action. For example, this could be your <code>/etc/init.d/my-java-program</code>:</p> <pre><code>#!/bin/sh case "$1" in start) java /path/to/my/java/program.jar &amp; echo $! &gt; /var/run/my-java-program.pid ;; stop) if [ ! -f /var/run/my-java-program.pid ]; then echo "my-java-program: not running" exit 1 fi kill -TERM `cat /var/run/my-java-program.pid` ;; reload) if [ ! -f /var/run/my-java-program.pid ]; then echo "my-java-program: not running" exit 1 fi kill -HUP `cat /var/run/my-java-program.pid` ;; *) echo "Usage: /etc/init.d/my-java-program {start|stop|reload}" exit 1 ;; esac exit 0 </code></pre> <p>You can now start your application by running <code>/etc/init.d/my-java-program start</code>, or on CentOS, you can also use service my-java-program start`.</p>
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    1. POWhat should a Java program listen for, to be a good Linux service?
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    1. USEdward Thomson
    1. USEdward Thomson
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    1. POWhat should a Java program listen for, to be a good Linux service?
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    1. COThanks Edward - so does that mean I can run `service <someService> {start|stop}` on any of my Java processes? I ask because this is how one starts/stops Tomcat politely, and I'd like my Java app to behave the same.
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    2. COI'm not completely familiar with the CentOS `service` mechanism. But on Debian and Ubuntu, I use the `/etc/init.d/myProgram start` and `stop` mechanisms without any problem.
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    3. COThanks again - I'm really not trying to be difficult here, I'm just having a tough time understanding the connection between how a shell-level call (either `service <service> start` or `start <service>` in your case) maps to Java being kickstarted and fed the application as an argument. I think once I understand that relation I'll be all set. Thanks again for such amazing help!
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