Check JVM settings of running java process

If you want to check the configuration of a running JVM process you can use jcmd.

1. List the running processes:

   $ jcmd -l
   1 /app.jar
   140 jdk.jcmd/sun.tools.jcmd.JCmd -l
   

   The first column shows the PID of the process.

2. Print system configuration with the PID:

   $ jcmd 1 VM.system_properties
   1:
   #Thu Jan 26 10:34:20 UTC 2023
   java.specification.version=17
   sun.jnu.encoding=UTF-8
   java.class.path=/app.jar
   java.vm.vendor=Eclipse Adoptium
   sun.arch.data.model=64
   catalina.useNaming=false
   java.vendor.url=https\://adoptium.net/
   user.timezone=Etc/UTC
   os.name=Linux
   java.vm.specification.version=17
   sun.java.launcher=SUN_STANDARD
   user.country=US
   sun.boot.library.path=/opt/java/openjdk/lib
   sun.java.command=/app.jar
   jdk.debug=release
   sun.cpu.endian=little
   user.home=/home/spring
   user.language=en
   java.specification.vendor=Oracle Corporation
   java.version.date=2023-01-17
   java.home=/opt/java/openjdk
   file.separator=/
   java.vm.compressedOopsMode=32-bit
   line.separator=\n
   java.specification.name=Java Platform API Specification
   java.vm.specification.vendor=Oracle Corporation
   FILE_LOG_CHARSET=UTF-8
   java.awt.headless=true
   java.protocol.handler.pkgs=org.springframework.boot.loader
   sun.management.compiler=HotSpot 64-Bit Tiered Compilers
   java.runtime.version=17.0.6+10
   user.name=spring
   path.separator=\:
   os.version=5.4.219-126.411.amzn2.x86_64
   java.runtime.name=OpenJDK Runtime Environment
   file.encoding=UTF-8
   java.vm.name=OpenJDK 64-Bit Server VM
   java.vendor.version=Temurin-17.0.6+10
   java.vendor.url.bug=https\://github.com/adoptium/adoptium-support/issues
   java.io.tmpdir=/tmp
   catalina.home=/tmp/tomcat.8080.11647654595355715119
   java.version=17.0.6
   user.dir=/
   os.arch=amd64
   java.vm.specification.name=Java Virtual Machine Specification
   PID=1
   CONSOLE_LOG_CHARSET=UTF-8
   catalina.base=/tmp/tomcat.8080.11647654595355715119
   native.encoding=UTF-8
   java.library.path=/usr/java/packages/lib\:/usr/lib64\:/lib64\:/lib\:/usr/lib
   java.vm.info=mixed mode, sharing
   java.vendor=Eclipse Adoptium
   java.vm.version=17.0.6+10
   sun.io.unicode.encoding=UnicodeLittle
   java.class.version=61.0
   

3. Print flags of the process with PID:

   $  jcmd 1 VM.flags
   -XX:CICompilerCount=2 -XX:InitialHeapSize=8388608 -XX:MaxHeapSize=134217728 -XX:MaxNewSize=44695552 -XX:MinHeapDeltaBytes=196608 -XX:MinHeapSize=8388608 -XX:NewSize=2752512 -XX:NonNMethodCodeHeapSize=5826188 -XX:NonProfiledCodeHeapSize=122916026 -XX:OldSize=5636096 -XX:ProfiledCodeHeapSize=122916026 -XX:ReservedCodeCacheSize=251658240 -XX:+SegmentedCodeCache -XX:SoftMaxHeapSize=134217728 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseFastUnorderedTimeStamps -XX:+UseSerialGC