【HotSpot】 jstatd

jstatd(1)                      General Commands Manual                      jstatd(1)

Name
       jstatd - Virtual Machine jstat Daemon 虚拟机运行状态

SYNOPSIS
       jstatd [ 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 creation
       and termination of instrumented HotSpot Java virtual machines (JVMs) and  pro‐
       vides  a  interface to allow remote monitoring tools to attach to JVMs running
       on the local host.   
	这个工具是远程接口调用工具，说明了JVM虚拟机HotSpot的启动和终止管理，同时提供了一个接口来允许管理工具绑定到运行着的本地虚拟机上

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 application 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 internal RMI registry can be inhibited by specify‐ ing 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 Windows 98 and Win‐ dows ME platforms.这个工具在未来的JDK版本中可能会被弃用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.当存在一个RMI时就不创建 -p port Port number where the RMI registry is expected to be found, or, if not found, created if -nr is not specified.RMI所希望被发现的注册端口，如果没被发现就创建 -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 appropriate native access permissions. Therefor the jstatd process must be running with the same user credentials as the target JVMs. Some user credentials, such as the root user in UNIX(TM) based systems, have permission to access the instru‐ mentation 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 instrumentation export by all JVMs for which the jstatd process has access permissions to any user on the network. This exposure may be undesireable in your environment and local security policies should be considered before starting the jstatd process, particularly in production environments or on unsecure networks. The jstatd server installs an instance of RMISecurityPolicy if no other secu‐ rity manager has been installed and therefore requires a security policy file to be specified. The policy file must conform to the default policy implemen‐ tation'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 customized 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 inter‐ face.EXAMPLES Here are some examples of starting jstatd. Note that the jstatd scripts auto‐ matically start the server in the background. Using Internal RMI Registry This example demonstrates starting jstatd with an internal RMI registry. 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 registry 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 monitoring server activities. jstatd -J-Djava.security.policy=all.policy -J-Djava.rmi.server.logCalls=trueSEE 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/technotes/tools/index.html#rmi - the Java Remote Object Registry 18 Jul 2013 jstatd(1)