JSTATD(1) JDK Commands JSTATD(1)
NAME
jstatd - monitor the creation and termination of instrumented Java
HotSpot VMs
SYNOPSIS
Note: This command is experimental and unsupported.
jstatd [options]
options
This represents the jstatd command-line options. See Options
for the jstatd Command.
DESCRIPTION
The jstatd command is an RMI server application that monitors for the
creation and termination of instrumented Java HotSpot VMs and provides
an interface to enable remote monitoring tools, jstat and jps, to at-
tach to JVMs that are running on the local host and collect information
about the JVM process.
The jstatd server requires an RMI registry on the local host. The js-
tatd server attempts to attach to the RMI registry on the default port,
or on the port you specify with the -p port option. If an RMI registry
is not found, then one is created within the jstatd application that's
bound to the port that's indicated by the -p port option or to the de-
fault RMI registry port when the -p port option is omitted. You can
stop the creation of an internal RMI registry by specifying the -nr op-
tion.
OPTIONS FOR THE JSTATD COMMAND
-nr This option does not attempt to create an internal RMI registry
within the jstatd process when an existing RMI registry isn't
found.
-p port
This option sets the port number where the RMI registry is ex-
pected to be found, or when not found, created if the -nr option
isn't specified.
-r rmiport
This option sets the port number to which the RMI connector is
bound. If not specified a random available port is used.
-n rminame
This option sets the 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, then
the name of the exported RMI object for each server can be made
unique by specifying this option. However, doing so requires
that the unique server name be included in the monitoring
client's hostid and vmid strings.
-Joption
This option passes a Java option to the JVM, where the option is
one of those described on the reference page for the Java appli-
cation launcher. For example, -J-Xms48m sets the startup memory
to 48 MB. See java.
SECURITY
The jstatd server can monitor only JVMs for which it has the appropri-
ate native access permissions. Therefore, the jstatd process must be
running with the same user credentials as the target JVMs. Some user
credentials, such as the root user in Linux and macOS operating sys-
tems, have permission to access the instrumentation exported by any JVM
on the system. A jstatd process running with such credentials can mon-
itor any JVM on the system, but introduces additional security con-
cerns.
The jstatd server doesn't provide any authentication of remote clients.
Therefore, running a jstatd server process exposes the instrumentation
export by all JVMs for which the jstatd process has access permissions
to any user on the network. This exposure might be undesirable in your
environment, and therefore, local security policies should be consid-
ered before you start the jstatd process, particularly in production
environments or on networks that aren't secure.
For security purposes, the jstatd server uses an RMI ObjectInputFilter
to allow only essential classes to be deserialized.
If your security concerns can't be addressed, then the safest action is
to not run the jstatd server and use the jstat and jps tools locally.
However, when using jps to get a list of instrumented JVMs, the list
will not include any JVMs running in docker containers.
REMOTE INTERFACE
The interface exported by the jstatd process is proprietary and guaran-
teed to change. Users and developers are discouraged from writing to
this interface.
EXAMPLES
The following are examples of the jstatd command. The jstatd scripts
automatically start the server in the background.
INTERNAL RMI REGISTRY
This example shows how to start a jstatd session with an internal RMI
registry. This example assumes that no other server is bound to the
default RMI registry port (port 1099).
jstatd
EXTERNAL RMI REGISTRY
This example starts a jstatd session with an external RMI registry.
rmiregistry&
jstatd
This example starts a jstatd session with an external RMI registry
server on port 2020.
jrmiregistry 2020&
jstatd -p 2020
This example starts a jstatd session with an external RMI registry
server on port 2020 and JMX connector bound to port 2021.
jrmiregistry 2020&
jstatd -p 2020 -r 2021
This example starts a jstatd session with an external RMI registry on
port 2020 that's bound to AlternateJstatdServerName.
rmiregistry 2020&
jstatd -p 2020 -n AlternateJstatdServerName
STOP THE CREATION OF AN IN-PROCESS RMI REGISTRY
This example starts a jstatd session that doesn't create an RMI reg-
istry when one isn't found. This example assumes an RMI registry is
already running. If an RMI registry isn't running, then an error mes-
sage is displayed.
jstatd -nr
ENABLE RMI LOGGING
This example starts a jstatd session with RMI logging capabilities en-
abled. This technique is useful as a troubleshooting aid or for moni-
toring server activities.
jstatd -J-Djava.rmi.server.logCalls=true
JDK 21 2023 JSTATD(1)
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