Getting the parameters of a running JVM

Question

Is there a way to get the parameters of a running JVM  Is there a command line tool like jstat which takes as input the pid of the JVM and returns its starting parameters  I am particularly interested in the -Xmx and -Xms values that were given when starting the JVM  Thank you   Edit  To clarify my constraints  The JVM we would like to check is running on a production server  That s why  we prefer the minimum disruption  We are able to monitor the JVM using jstat  and so we hope there s a similar simple solution to access the parameters   Edit  We also tried to get the parameters using jvisualvm  But in order to connect to a remote jvm  we need to run jstatd and modify the security settings of the JVM  which we found to be very disruptive and risky on a production server

User · Answer

You can use the JConsole command  or any other JMX client  to access that information

User · Answer

This technique applies for any java application running local or remote    Start your java application  Run JVisualVM found in you JDK  such as C  Program Files Java jdk1 8 0 05 bin jvisualvm exe   When this useful tool starts look at the list of running java application under the  Local  tree node  Double click  your application   pid  n    On the right side there will be inspection contents in tab for the  application  In the middle of the Overview tab you will see the JVM arguments for the application    jvisualvm can be found in any JDK since JDK 6 Update 7   Video tutorial on jvisualvm is here

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On linux  you can run this command and see the result    ps aux   grep  java

User · Answer

If you can do this in java  try   RuntimeMXBean  ManagementFactory  Example   RuntimeMXBean runtimeMXBean   ManagementFactory getRuntimeMXBean    List lt String gt  jvmArgs   runtimeMXBean getInputArguments    for  String arg   jvmArgs        System out println arg

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JConsole can do it  Also you can use a powerful jvisualVM tool  which also is included in JDK since 1 6 0 8

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You can use jps like  jps -lvm   prints something like  4050 com intellij idea Main -Xms128m -Xmx512m -XX MaxPermSize 250m -ea -Xbootclasspath a    lib boot jar -Djb restart code 88 4667 sun tools jps Jps -lvm -Dapplication home  opt java jdk1 6 0 22 -Xms8m

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Windows 10 or Windows Server 2016 provide such information in their standard task manager  A rare case for production  but if the target JVM is running on Windows  the simplest way to see its parameters is to press Ctrl Alt Delete  choose the Processes tab and add the Command line column  by clicking the right mouse button on any existing column header

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Alternatively  you can use jinfo  jinfo -flags  lt vmid gt   jinfo -sysprops  lt vmid gt

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If you are interested in getting the JVM parameters of a running java process  then just do kill -3 java-pid  You will get a core dump file in which you can find the jvm parameters used while launching the java application

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JAVA OPTIONS is an env variable that can be expanded  echo   JAVA OPTIONS

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On Linux   java -XX  PrintFlagsFinal -version   grep -iE  HeapSize PermSize ThreadStackSize    On Mac OSX   java -XX  PrintFlagsFinal -version   grep -iE  heapsize permsize threadstacksize    On Windows   C   gt java -XX  PrintFlagsFinal -version   findstr  i  HeapSize PermSize ThreadStackSize    Source  https   www mkyong com java find-out-your-java-heap-memory-size

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I am adding this new answer because as per JDK8 documentation jcmd is suggested approach now      It is suggested to use the latest utility  jcmd instead of the   previous jstack  jinfo  and jmap utilities for enhanced diagnostics   and reduced performance overhead    Below are commands to get your properties flags you want   jcmd pid VM system properties jcmd pid VM flags   We need pid  for this use jcmd -l  like below  username users-Air   javacode  jcmd -l  11441 Test  6294 Test  29197 jdk jcmd sun tools jcmd JCmd -l    Now time to use these pids to get properties flags you want  Command  jcmd 11441 VM system properties  11441   Tue Oct 17 12 44 50 IST 2017 gopherProxySet false awt toolkit sun lwawt macosx LWCToolkit file encoding pkg sun io java specification version 9 sun cpu isalist  sun jnu encoding UTF-8 java class path   java vm vendor Oracle Corporation sun arch data model 64 java vendor url http    java oracle com  user timezone Asia Kolkata java vm specification version 9 os name Mac OS X sun java launcher SUN STANDARD user country US sun boot library path  Library Java JavaVirtualMachines jdk-9 jdk Contents Home lib sun java command Test http nonProxyHosts local   local 169 254 16   169 254 16 jdk debug release sun cpu endian little user home  Users XXXX user language en java specification vendor Oracle Corporation java home  Library Java JavaVirtualMachines jdk-9 jdk Contents Home file separator   java vm compressedOopsMode Zero based line separator  n java specification name Java Platform API Specification java vm specification vendor Oracle Corporation java awt graphicsenv sun awt CGraphicsEnvironment sun management compiler HotSpot 64-Bit Tiered Compilers ftp nonProxyHosts local   local 169 254 16   169 254 16 java runtime version 9 181 user name XXXX path separator    os version 10 12 6 java runtime name Java TM  SE Runtime Environment file encoding UTF-8 java vm name Java HotSpot TM  64-Bit Server VM java vendor url bug http    bugreport java com bugreport  java io tmpdir  var folders dm gd6lc90d0hg220lzw m7krr00000gn T  java version 9 user dir  Users XXXX javacode os arch x86 64 java vm specification name Java Virtual Machine Specification java awt printerjob sun lwawt macosx CPrinterJob sun os patch level unknown MyParam 2 java library path  Users XXXX Library Java Extensions   Library Java Extensions   Network Library Java Extensions   System Library Java Extensions   usr lib java    java vm info mixed mode java vendor Oracle Corporation java vm version 9 181 sun io unicode encoding UnicodeBig java class version 53 0 socksNonProxyHosts local   local 169 254 16   169 254 16   Command   jcmd 11441 VM flags output   11441  -XX CICompilerCount 3 -XX ConcGCThreads 1 -XX G1ConcRefinementThreads 4 -XX G1HeapRegionSize 1048576 -XX InitialHeapSize 67108864 -XX MarkStackSize 4194304 -XX MaxHeapSize 1073741824 -XX MaxNewSize 643825664 -XX MinHeapDeltaBytes 1048576 -XX NonNMethodCodeHeapSize 5830092 -XX NonProfiledCodeHeapSize 122914074 -XX ProfiledCodeHeapSize 122914074 -XX ReservedCodeCacheSize 251658240 -XX  SegmentedCodeCache -XX -UseAOT -XX  UseCompressedClassPointers -XX  UseCompressedOops -XX  UseFastUnorderedTimeStamps -XX  UseG1GC    For more instructions of usages of jcmd  see my blog post

[java] Getting the parameters of a running JVM

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