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.

To clarify my constraints for the JVM, we would like to check if it 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.

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.

You can find a tool there : [JDK Tools and Utilities](http://docs.oracle.com/javase/8/docs/technotes/tools/index.html) — Guillaume Husta, Sep 04 '17 at 08:53

score 193 · Accepted Answer · edited Jan 10 '22 at 17:29

193

You can use jps like:

jps -lvm

It 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

edited Jan 10 '22 at 17:29

Peter Mortensen

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answered Mar 15 '11 at 19:55

Peter Lawrey

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Works like a charm. I also discovered the jinfo tool in the jdk which has a similar function – H-H Mar 16 '11 at 18:51
2

Notice that the output of `jps -lvm` might be misleading. Always double check with jinfo or other tool. The problem can be if "-XX" is passed like the normal program argument and ignored by JVM. This is the case if you use `java -jar my.jar -Xmx3g` instead of `java -Xmx3g -jar my.jar` – Juraj Martinka Jun 28 '17 at 15:02

score 71 · Answer 2 · edited Jan 10 '22 at 16:53

As per JDK 8 documentation jcmd is the suggested approach.

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 the PID. For this, use jcmd -l, like below

cd ~/javacode
jcmd -l

11441 Test
6294 Test
29197 jdk.jcmd/sun.tools.jcmd.JCmd -l

Now it is 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.

pid should be replaced with java process id, Linux os generally we get it by “ps -ef | grep jdk” , if you see multiple processes by this then ask a new question or try to google it — Vipin, Aug 06 '18 at 17:11

score 38 · Answer 3 · edited Jan 10 '22 at 16:41

38

On Linux:

java -XX:+PrintFlagsFinal -version | grep -iE 'HeapSize|PermSize|ThreadStackSize'

On Mac OS X:

java -XX:+PrintFlagsFinal -version | grep -iE 'heapsize|permsize|threadstacksize'

On Windows:

java -XX:+PrintFlagsFinal -version | findstr /i "HeapSize PermSize ThreadStackSize"

Source: Find out your Java heap memory size

edited Jan 10 '22 at 16:41

Peter Mortensen

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answered Aug 17 '16 at 21:19

Diego López

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This does not address the question which is to get JVM flags of a running process – harogaston Aug 03 '21 at 15:22

score 30 · Answer 4 · answered Jul 01 '13 at 08:36

30

Alternatively, you can use jinfo

jinfo -flags <vmid> 
jinfo -sysprops <vmid>

answered Jul 01 '13 at 08:36

Jarek Przygódzki

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This utility is unsupported and may or may not be available in future versions of the JDK. – GoYun.Info May 31 '16 at 19:30
`-flags` option does not exist in OpenJDK 64-Bit Server VM (build 1.8.0_111-internal-alpine-r0-b14) (current `java:8u111-jdk-alpine` Docker image) – Anthony O. Feb 26 '18 at 09:53
I wrote this answer with Java 6/7 in mind. Beyond that jinfo is unreliable, but `flags` works with official Docker java image based on Debian Jessie `docker run --rm -it java:8u111-jdk java -version && jinfo -h` – Jarek Przygódzki Feb 27 '18 at 12:41
1

Perhaps it is time for an update of the answer? – Peter Mortensen Jan 10 '22 at 17:29

score 23 · Answer 5 · edited Jan 10 '22 at 17:26

23

If you can do this in Java, try:

RuntimeMXBean

ManagementFactory

Example:

RuntimeMXBean runtimeMXBean = ManagementFactory.getRuntimeMXBean();
List<String> jvmArgs = runtimeMXBean.getInputArguments();
for (String arg : jvmArgs) {
    System.out.println(arg);
}

edited Jan 10 '22 at 17:26

Peter Mortensen

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answered Mar 15 '11 at 19:53

lukastymo

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Will only provide values if it was passed, hence no default settings. – Behe Feb 08 '16 at 17:18

score 19 · Answer 6 · edited Jan 10 '22 at 17:06

19

On Linux, you can run this command and see the result:

ps aux | grep "java"

edited Jan 10 '22 at 17:06

Peter Mortensen

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answered Nov 21 '19 at 08:53

Etienne

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My company uses Red Hat Linux and I have very limited access to the system. ps aux | grep "java" command lists all the java commands with their jvm arguments and we can even grep the exact jvm argument if needed. This is really useful in case any other tools such as jps, jcmd etc are not available/accessible. – AGan Mar 19 '20 at 20:31

score 12 · Answer 7 · edited Jan 10 '22 at 17:28

12

JConsole can do it. Also you can use the powerful Java VisualVM tool, which also is included in JDK since 1.6.0.8.

edited Jan 10 '22 at 17:28

Peter Mortensen

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answered Mar 15 '11 at 19:53

Vladimir Ivanov

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score 5 · Answer 8 · edited Jan 10 '22 at 16:56

5

Windows 10 or Windows Server 2016 provide such information in their standard Task Manager.

It is 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).

edited Jan 10 '22 at 16:56

Peter Mortensen

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answered Jan 22 '19 at 15:57

Roman Khomyshynets

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mayqueen · Answer 9 · 2022-04-10T21:42:58.140

In case of really small containers (no ps, tree, jcmd etc.) you can also try to guess process id (by listing ls -l /proc) and then read parameters from specific process: cat /proc/<pid>/cmdline.

example:

$ cat /proc/614/cmdline

may print something like:

java-D[Standalone]-server-Xms64m-Xmx512m-XX:MetaspaceSize=96M-XX:MaxMetaspaceSize=256m-Djava.net.preferIPv4Stack=true-Djboss.modules.system.pkgs=org.jboss.byteman-Djava.awt.headless=true-Dkeycloak.profile=preview-Djboss.as.management.blocking.timeout=1800-Djboss.node.name=keycloak1loak/modulesorg.jboss.as.standalone

To read the same for all processes (discarding any permission errors and processes that dissapeared during command execution):

for i in $(find /proc/ -maxdepth 2 -type f -name cmdline -exec ls {} 2>/dev/null \; ); do echo "$i"; cat $i 2>/dev/null; echo; echo; done

Note: It's not narrowed down to java processes only - you can do that using grep.

score 1 · Answer 10 · edited Jan 10 '22 at 17:30

This technique applies for any Java applications running local or remote.

Start your Java application.
Run Java VisualVM 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 applications under the "Local" tree node.
Double click [your application] (pid [n]).
On the right side, there will be inspection contents in a tab for the application. In the middle of the Overview tab, you will see the JVM arguments for the application.

Java VisualVM can be found in any JDK since JDK 6 Update 7. Video tutorial on Java VisualVM is here.

OP explicitly stated that jvisualvm was not an option. – Olivier Gérardin May 13 '20 at 09:49 — Olivier Gérardin, May 13 '20 at 09:49

score 1 · Answer 11 · edited Jan 10 '22 at 17:00

1

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.

edited Jan 10 '22 at 17:00

Peter Mortensen

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answered Apr 02 '19 at 14:50

lambzee

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score 0 · Answer 12 · answered Mar 15 '11 at 19:57

0

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

answered Mar 15 '11 at 19:57

nfechner

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score 0 · Answer 13 · edited Jan 10 '22 at 17:10

0

_JAVA_OPTIONS is an environment variable that can be expanded:

echo $_JAVA_OPTIONS

edited Jan 10 '22 at 17:10

Peter Mortensen

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answered Aug 14 '20 at 01:34

z atef

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score 0 · Answer 14 · answered Aug 09 '22 at 01:05

0

I usually do ps -ef | grep java. It outputs the process with PID + the used command line parameters.

answered Aug 09 '22 at 01:05

Battle_Slug

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Getting the parameters of a running JVM

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