英文全称
Java Virtual Machine Java Configuration Info 显示虚拟机配置信息，可以用来查看正在运行的Java应用程序的扩展参数，甚至支持在运行时，修改部分参数
jinfo的作用是实时地查看和调整虚拟机的各项参数。使用jps的命令的-v参数可以查看虚拟机启动时显示指定的参数列表，但如果想知道未被显示指定的参数的系统默认值，就可以用到jinfo命令来查看
命令格式
jinfo [option] pid选项
option具体选项及作用如下：
-flags 查看jvm的参数
-sysprops 查看java系统参数
-flag [+|-] 修改正在运行的Java应用程序JVM参数，其中+是开启对应参数，-是关闭对应参数
示例
Tips ：需要有JDK环境
- -flags 查看jvm参数
[root@iZbp13vdh76h8tevitqolvZ ~]# jps -l
25273 org.apache.catalina.startup.Bootstrap
10922 sun.tools.jps.Jps
1914 com.aliyun.tianji.cloudmonitor.Application
[root@iZbp13vdh76h8tevitqolvZ ~]# jinfo -flags 25273
Attaching to process ID 25273, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.66-b17
Non-default VM flags: -XX:CICompilerCount=2 -XX:InitialHeapSize=16777216 -XX:MaxHeapSize=262144000 -XX:MaxNewSize=87359488 -XX:MinHeapDeltaBytes=196608 -XX:NewSize=5570560 -XX:OldSize=11206656 -XX:-PrintGC -XX:+UseCompressedClassPointers -XX:+UseCompressedOops
Command line: -Djava.util.logging.config.file=/usr/local/tools/apache-tomcat-8.0.32/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.endorsed.dirs=/usr/local/tools/apache-tomcat-8.0.32/endorsed -Dcatalina.base=/usr/local/tools/apache-tomcat-8.0.32 -Dcatalina.home=/usr/local/tools/apache-tomcat-8.0.32 -Djava.io.tmpdir=/usr/local/tools/apache-tomcat-8.0.32/temp- -sysprops 查看java系统参数
[root@iZbp13vdh76h8tevitqolvZ ~]# jinfo -sysprops 25273
Attaching to process ID 25273, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.66-b17
java.runtime.name = Java(TM) SE Runtime Environment
java.vm.version = 25.66-b17
sun.boot.library.path = /usr/java/jdk1.8.0_66/jre/lib/amd64
shared.loader =
java.vendor.url = http://java.oracle.com/
java.vm.vendor = Oracle Corporation
path.separator = :
file.encoding.pkg = sun.io
java.vm.name = Java HotSpot(TM) 64-Bit Server VM
java.util.logging.config.file = /usr/local/tools/apache-tomcat-8.0.32/conf/logging.properties
tomcat.util.buf.StringCache.byte.enabled = true
sun.os.patch.level = unknown
sun.java.launcher = SUN_STANDARD
user.country = US
tomcat.util.scan.StandardJarScanFilter.jarsToScan = log4j-core*.jar,log4j-taglib*.jar,log4javascript*.jar
user.dir = /usr/local/tools/apache-tomcat-8.0.32/bin
java.vm.specification.name = Java Virtual Machine Specification
java.runtime.version = 1.8.0_66-b17
java.awt.graphicsenv = sun.awt.X11GraphicsEnvironment
os.arch = amd64
java.endorsed.dirs = /usr/local/tools/apache-tomcat-8.0.32/endorsed
line.separator =
java.io.tmpdir = /usr/local/tools/apache-tomcat-8.0.32/temp
java.vm.specification.vendor = Oracle Corporation
java.util.logging.manager = org.apache.juli.ClassLoaderLogManager
java.naming.factory.url.pkgs = org.apache.naming
os.name = Linux
sun.jnu.encoding = UTF-8
java.library.path = /usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
java.class.version = 52.0
java.specification.name = Java Platform API Specification
sun.management.compiler = HotSpot 64-Bit Tiered Compilers
os.version = 2.6.32-431.23.3.el6.x86_64
user.home = /root
user.timezone = Asia/Shanghai
catalina.useNaming = true
java.awt.printerjob = sun.print.PSPrinterJob
file.encoding = UTF-8
java.specification.version = 1.8
tomcat.util.scan.StandardJarScanFilter.jarsToSkip = bootstrap.jar,commons-daemon.jar,tomcat-juli.jar,annotations-api.jar,el-api.jar,jsp-api.jar,servlet-api.jar,websocket-api.jar,catalina.jar,catalina-ant.jar,catalina-ha.jar,catalina-storeconfig.jar,catalina-tribes.jar,jasper.jar,jasper-el.jar,ecj-*.jar,tomcat-api.jar,tomcat-util.jar,tomcat-util-scan.jar,tomcat-coyote.jar,tomcat-dbcp.jar,tomcat-jni.jar,tomcat-websocket.jar,tomcat-i18n-en.jar,tomcat-i18n-es.jar,tomcat-i18n-fr.jar,tomcat-i18n-ja.jar,tomcat-juli-adapters.jar,catalina-jmx-remote.jar,catalina-ws.jar,tomcat-jdbc.jar,tools.jar,commons-beanutils*.jar,commons-codec*.jar,commons-collections*.jar,commons-dbcp*.jar,commons-digester*.jar,commons-fileupload*.jar,commons-httpclient*.jar,commons-io*.jar,commons-lang*.jar,commons-logging*.jar,commons-math*.jar,commons-pool*.jar,jstl.jar,taglibs-standard-spec-*.jar,geronimo-spec-jaxrpc*.jar,wsdl4j*.jar,ant.jar,ant-junit*.jar,aspectj*.jar,jmx.jar,h2*.jar,hibernate*.jar,httpclient*.jar,jmx-tools.jar,jta*.jar,log4j*.jar,mail*.jar,slf4j*.jar,xercesImpl.jar,xmlParserAPIs.jar,xml-apis.jar,junit.jar,junit-*.jar,ant-launcher.jar,cobertura-*.jar,asm-*.jar,dom4j-*.jar,icu4j-*.jar,jaxen-*.jar,jdom-*.jar,jetty-*.jar,oro-*.jar,servlet-api-*.jar,tagsoup-*.jar,xmlParserAPIs-*.jar,xom-*.jar
catalina.home = /usr/local/tools/apache-tomcat-8.0.32
user.name = root
java.class.path = /usr/local/tools/apache-tomcat-8.0.32/bin/bootstrap.jar:/usr/local/tools/apache-tomcat-8.0.32/bin/tomcat-juli.jar
java.naming.factory.initial = org.apache.naming.java.javaURLContextFactory
package.definition = sun.,java.,org.apache.catalina.,org.apache.coyote.,org.apache.jasper.,org.apache.naming.,org.apache.tomcat.
java.vm.specification.version = 1.8
sun.arch.data.model = 64
sun.java.command = org.apache.catalina.startup.Bootstrap start
java.home = /usr/java/jdk1.8.0_66/jre
user.language = en
java.specification.vendor = Oracle Corporation
awt.toolkit = sun.awt.X11.XToolkit
java.vm.info = mixed mode
java.version = 1.8.0_66
java.ext.dirs = /usr/java/jdk1.8.0_66/jre/lib/ext:/usr/java/packages/lib/ext
sun.boot.class.path = /usr/java/jdk1.8.0_66/jre/lib/resources.jar:/usr/java/jdk1.8.0_66/jre/lib/rt.jar:/usr/java/jdk1.8.0_66/jre/lib/sunrsasign.jar:/usr/java/jdk1.8.0_66/jre/lib/jsse.jar:/usr/java/jdk1.8.0_66/jre/lib/jce.jar:/usr/java/jdk1.8.0_66/jre/lib/charsets.jar:/usr/java/jdk1.8.0_66/jre/lib/jfr.jar:/usr/java/jdk1.8.0_66/jre/classes
server.loader =
java.vendor = Oracle Corporation
catalina.base = /usr/local/tools/apache-tomcat-8.0.32
file.separator = /
java.vendor.url.bug = http://bugreport.sun.com/bugreport/
common.loader = "${catalina.base}/lib","${catalina.base}/lib/*.jar","${catalina.home}/lib","${catalina.home}/lib/*.jar"
sun.io.unicode.encoding = UnicodeLittle
sun.cpu.endian = little
package.access = sun.,org.apache.catalina.,org.apache.coyote.,org.apache.jasper.,org.apache.tomcat.
sun.cpu.isalist = - -flag [+|-] 开启PrintGCDetails参数
先查看当前tomcat进程jvm参数开启情况
[root@iZbp13vdh76h8tevitqolvZ ~]# jinfo -flags 25273
Attaching to process ID 25273, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.66-b17
Non-default VM flags: -XX:CICompilerCount=2 -XX:InitialHeapSize=16777216 -XX:MaxHeapSize=262144000 -XX:MaxNewSize=87359488 -XX:MinHeapDeltaBytes=196608 -XX:NewSize=5570560 -XX:OldSize=11206656 -XX:-PrintGC -XX:+UseCompressedClassPointers -XX:+UseCompressedOops
Command line: -Djava.util.logging.config.file=/usr/local/tools/apache-tomcat-8.0.32/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.endorsed.dirs=/usr/local/tools/apache-tomcat-8.0.32/endorsed -Dcatalina.base=/usr/local/tools/apache-tomcat-8.0.32 -Dcatalina.home=/usr/local/tools/apache-tomcat-8.0.32 -Djava.io.tmpdir=/usr/local/tools/apache-tomcat-8.0.32/temp可以看到是没有开启PrintGCDetails参数的，执行jinfo -flag +PrintGCDetails 25273开启PrintGCDetails参数：
[root@iZbp13vdh76h8tevitqolvZ ~]# jinfo -flag +PrintGCDetails 25273
[root@iZbp13vdh76h8tevitqolvZ ~]# jinfo -flags 25273
Attaching to process ID 25273, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.66-b17
Non-default VM flags: -XX:CICompilerCount=2 -XX:InitialHeapSize=16777216 -XX:MaxHeapSize=262144000 -XX:MaxNewSize=87359488 -XX:MinHeapDeltaBytes=196608 -XX:NewSize=5570560 -XX:OldSize=11206656 -XX:-PrintGC -XX:+PrintGCDetails -XX:+UseCompressedClassPointers -XX:+UseCompressedOops
Command line: -Djava.util.logging.config.file=/usr/local/tools/apache-tomcat-8.0.32/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.endorsed.dirs=/usr/local/tools/apache-tomcat-8.0.32/endorsed -Dcatalina.base=/usr/local/tools/apache-tomcat-8.0.32 -Dcatalina.home=/usr/local/tools/apache-tomcat-8.0.32 -Djava.io.tmpdir=/usr/local/tools/apache-tomcat-8.0.32/tempPrintGCDetails参数已开启
- -flag [+|-] 关闭PrintGCDetails参数
[root@iZbp13vdh76h8tevitqolvZ ~]# jinfo -flag -PrintGCDetails 25273
[root@iZbp13vdh76h8tevitqolvZ ~]# jinfo -flags 25273
Attaching to process ID 25273, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.66-b17
Non-default VM flags: -XX:CICompilerCount=2 -XX:InitialHeapSize=16777216 -XX:MaxHeapSize=262144000 -XX:MaxNewSize=87359488 -XX:MinHeapDeltaBytes=196608 -XX:NewSize=5570560 -XX:OldSize=11206656 -XX:-PrintGC -XX:-PrintGCDetails -XX:+UseCompressedClassPointers -XX:+UseCompressedOops
Command line: -Djava.util.logging.config.file=/usr/local/tools/apache-tomcat-8.0.32/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.endorsed.dirs=/usr/local/tools/apache-tomcat-8.0.32/endorsed -Dcatalina.base=/usr/local/tools/apache-tomcat-8.0.32 -Dcatalina.home=/usr/local/tools/apache-tomcat-8.0.32 -Djava.io.tmpdir=/usr/local/tools/apache-tomcat-8.0.32/temp