jstatd(1)jstatd(1)Namejstatd - Virtual Machine jstat Daemon
SYNOPSISjstatd [ options ]
PARAMETERS
options
Command-line options. The options may be in any order. If there
are redundant or contradictory options, the last option specified
will take precedence.
DESCRIPTION
The jstatd tool is an RMI server application that monitors for the cre‐
ation and termination of instrumented HotSpot Java virtual machines
(JVMs) and provides a interface to allow remote monitoring tools to
attach to JVMs running on the local host.
The jstatd server requires the presence of an RMI registry on the local
host. The jstatd server will attempt to attach to the RMI registry on
the default port, or on the port indicated by the -p port option. If an
RMI registry is not found, one will be created within the jstatd appli‐
cation bound to the port indicated by the -p port option or to the
default RMI registry port if -p port is omitted. Creation of an inter‐
nal RMI registry can be inhibited by specifying the -nr option.
NOTE: This utility is unsupported and may or may not be available in
future versions of the JDK. It is not currently available on the Win‐
dows 98 and Windows ME platforms.
OPTIONS
The jstatd command supports the following options:
-nr
Do not attempt to create an internal RMI registry within the
jstatd process when an existing RMI registry is not found.
-p port
Port number where the RMI registry is expected to be found, or,
if not found, created if -nr is not specified.
-n rminame
Name to which the remote RMI object is bound in the RMI registry.
The default name is JStatRemoteHost. If multiple jstatd servers
are started on the same host, the name of the exported RMI object
for each server can be made unique by specifying this option.
However, doing so will require that the unique server name be
included in the monitoring client's hostid and vmid strings.
-Joption
Pass option to the java launcher called by javac. For example,
-J-Xms48m sets the startup memory to 48 megabytes. It is a common
convention for -J to pass options to the underlying VM executing
applications written in Java.
SECURITY
The jstatd server can only monitor JVMs for which it has the appropri‐
ate native access permissions. Therefor the jstatd process must be run‐
ning with the same user credentials as the target JVMs. Some user cre‐
dentials, such as the root user in UNIX(TM) based systems, have permis‐
sion to access the instrumentation exported by any JVM on the system. A
jstatd process running with such credentials can monitor any JVM on the
system, but introduces additional security concerns.
The jstatd server does not provide any authentication of remote
clients. Therefore, running a jstatd server process exposes the instru‐
mentation export by all JVMs for which the jstatd process has access
permissions to any user on the network. This exposure may be undesire‐
able in your environment and local security policies should be consid‐
ered before starting the jstatd process, particularly in production
environments or on unsecure networks.
The jstatd server installs an instance of RMISecurityPolicy if no other
security manager has been installed and therefore requires a security
policy file to be specified. The policy file must conform to the
default policy implementation's Policy File Syntax @
http://docs.oracle.com/javase/7/docs/technotes/guides/security/Policy‐
Files.html.
The following policy file will allow the jstatd server to run without
any security exceptions. This policy is less liberal then granting all
permissions to all codebases, but is more liberal than a policy that
grants the minimal permissions to run the jstatd server.
grant codebase "file:${java.home}/../lib/tools.jar" {
permission java.security.AllPermission;
};
To use this policy, copy the text into a file called jstatd.all.policy
and run the jstatd server as follows:
jstatd -J-Djava.security.policy=jstatd.all.policy
For sites with more restrictive security practices, it is possible to
use a custom policy file to limit access to specific trusted hosts or
networks, though such techniques are subject to IP addreess spoofing
attacks. If your security concerns cannot be addressed with a custom‐
ized policy file, then the safest action is to not run the jstatd
server and use the jstat and jps tools locally.
REMOTE INTERFACE
The interface exported by the jstatd process is proprietary and is
guaranteed to change. Users and developers are discouraged from writing
to this interface.
EXAMPLES
Here are some examples of starting jstatd. Note that the jstatd scripts
automatically start the server in the background.
Using Internal RMI Registry
This example demonstrates starting jstatd with an internal RMI reg‐
istry. This example assumes that no other server is bound to the
default RMI Registry port (port 1099).
jstatd -J-Djava.security.policy=all.policy
Using External RMI Registry
This example demonstrates starting jstatd with a external RMI registry.
rmiregistry&
jstatd -J-Djava.security.policy=all.policy
This example demonstrates starting jstatd with an external RMI registry
server on port 2020.
rmiregistry 2020&
jstatd -J-Djava.security.policy=all.policy -p 2020
This example demonstrates starting jstatd with an external RMI registry
on port 2020, bound to name AlternateJstatdServerName.
rmiregistry 2020&
jstatd -J-Djava.security.policy=all.policy -p 2020 -n AlternateJstatdServerName
Inhibiting creation of an in-process RMI registry
This example demonstrates starting jstatd such that it will not create
a RMI registry if one is not found. This example assumes an RMI reg‐
istry is already running. If it is not, an appropriate error message is
emitted.
jstatd -J-Djava.security.policy=all.policy -nr
Enabling RMI logging capabilities.
This example demonstrates starting jstatd with RMI logging capabilities
enabled. This technique is useful as a troubleshooting aid or for moni‐
toring server activities.
jstatd -J-Djava.security.policy=all.policy -J-Djava.rmi.server.logCalls=true
SEE ALSO
o java(1) - the Java Application Launcher
o jps(1) - the Java Process Status Application
o jstat(1) - the Java Virtual Machine Statistics Monitoring Tool
o rmiregistry @
http://docs.oracle.com/javase/7/docs/tech‐
notes/tools/index.html#rmi - the Java Remote Object Registry
16 Mar 2012 jstatd(1)
