System properties management

If you really want a quick and simple way to change a system property, you can use the script console

System.setProperty("hudson.remoting.Launcher.pingIntervalSec", 0)

But that won't survive a restart. To make it permanent, add the setting to the java args. For me (CentOS, Jenkins 2.7.1) that's a line about halfway down /etc/sysconfig/jenkins (for other distributions I believe it's /etc/default/jenkins) where you should add your option to the existing list like this:

JENKINS_JAVA_OPTIONS="-Djava.awt.headless=true -Dhudson.remoting.Launcher.pingIntervalSec=0"

You'll have to restart Jenkins after you make that change (thanks Mark Tickner)

If you run Jenkins on windows as a service without tomcat, you can edit jenkins.xml. Add the property in <service><arguments> before the -jar. Than restart the service.

<service>
    <!-- ... -->
    <arguments>-Xrs -Xmx256m  -Dhudson.lifecycle=hudson.lifecycle.WindowsServiceLifecycle  -Dhudson.tasks.MailSender.SEND_TO_UNKNOWN_USERS=true  -Dhudson.tasks.MailSender.SEND_TO_USERS_WITHOUT_READ=true  -jar "%BASE%\jenkins.war" --httpPort=8080 --webroot="%BASE%\war"</arguments>

The system properties available and how to set them are listed on the wiki:
https://wiki.jenkins-ci.org/display/JENKINS/Features+controlled+by+system+properties

To disable slave pinging, you can set hudson.remoting.Launcher.pingIntervalSec to 0.

System properties can be set in the same way as with any other Java program, e.g.:
java -Dhudson.remoting.Launcher.pingIntervalSec=0 -jar jenkins.war