Section: User Commands (1)
Updated: 23 Aug 2014
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javaws - a Java Web Start client  


javaws [-run-options] jnlp-file
javaws [-control-option]  


javaws is an implementation of a JNLP client. It uses a JNLP (Java Network Launch Protocol) file to securely run a remote Java application or a Java applet. This implementation of javaws is from the IcedTea project and is based on the NetX project.

A JNLP file is an XML file that describes how to securely run a remote Java application or a Java applet.



When specifying options, the name of the JNLP file must be the last argument to javaws - all the options must precede it.

The JNLP-file can either be a URL or a local path.

Control Options

By default javaws will launch the JNLP file specified on the command line. The control options can be used to change this behaviour.

Shows about dialog.
Shows the trusted certificate viewer. This allows a user to list, examine, remove or export trusted certificates. Note that this only reflects the certificates trusted by javaws and not any other certificates or programs.

Run Options

In the default mode, the following run-options can be used:

Prints out version and exit
-arg arg
Adds an application argument before launching.
-param name=value
Adds an applet parameter before launching.
-property name=value
Sets a system property before launching.
-update seconds
Check for applet/application updates if "seconds" seconds have elapsed since the last check.
Display the GPL license and exit.
Enable verbose output. Very useful in debugging.
Disables the secure runtime environment.
Disables checking for updates.
Disables the download window and other extra UI elements.
Enables strict checking of JNLP file format. Any deviations from the JNLP DTD will cause javaws to abort.
Enables stricter XML validity checking for JNLP files.
Enables following 301, 302, 303, 307 and 308 HTTP redirects for javaws applications.
IcedTea-Web will not attempt to connect to the network to check for or download newer versions of the requested applet or application. Locally cached application files will be used instead, if available. The application itself may still establish its own network connections.
Do not create another JVM, even if the JNLP file asks for running in a separate JVM. This is useful for debugging.
Clean the JNLP application cache.
Skip jar header verification.
This passes along java-option to the Java binary (JVM) which javaws will be executed within. For example, to make javaws run with a max heap size of 80m, use -J-Xmx80m.
Print the javaws help message and exit.



$XDG_CONFIG_DIR/icedtea-web/ specifies the settings used by javaws

$XDG_CONFIG_DIR/icedtea-web/log (may be set to different location by you) contains file log files (if enabled). itw-cplugin-date_time.log for native part of plugin, itw-javantx-date_time.log for everything else.

$XDG_CONFIG_DIR/icedtea-web/security/java.policy contains the user's security policy, which may grant extra permissions to applets.

$XDG_CONFIG_DIR/icedtea-web/security/trusted.*certs contains various stored certificates.

$XDG_CACHE_DIR/icedtea-web/cache contains cached runtime entries (may be modified by the user).

$XDG_CACHE_DIR/icedtea-web/pcache contains saved application data.

$XDG_CACHE_DIR/icedtea-web/tmp contains temporary runtime files.

$XDG_RUNTIME_DIR/icedteaplugin-user-*/ contains in and out pipe for native<->java communication and (if enabled) debugging pipe

Where $XDG_CONFIG_DIR, $XDG_CACHE_DIR and $XDG_RUNTIME_DIR are defined as $HOME/.config, $HOME/.cache and either /tmp or /var/tmp by default. This is in accordance with the FreeDesktop Base Directory Specification:



There aren't any known bugs. If you come across one, please file it at
Please run javaws in debug (via -verbose switch, itweb-settings configuration, or ICEDTEAPLUGIN_DEBUG environment variable set to true) mode and include that output (best is from java console) with URL to JNLP or HTML file (not the JNLP/HTML file or application itself) when filing out the bug report.



Originally written by Jon. A. Maxwell.
Currently maintained by the IcedTea contributors. See javaws -about for more info



java(1), itweb-settings(1)