jdk8下：jps命令

列出正在运行的虚拟机进程，并显示虚拟机执行主类（main class, main()函数所在的类）名称，以及这些进程的本地虚拟机Id（LVMID）。

使用方法：在当前命令行下打jps(jps存放在JAVA_HOME/bin/jps，使用时为了方便请将JAVA_HOME/bin/加入到Path) 。

➜  ~ jps
7808 Launcher
2803 Main
5635 RemoteJdbcServer
5254 RemoteJdbcServer
13640 Jps
3400 RemoteMavenServer
5480 Main
7694 CosumerAckTest
22606 RemoteJdbcServer
4287 RemoteJdbcServer

参数

-q 只显示pid，不显示class名称,jar文件名和传递给main方法的参数

➜  ~ jps -q
7808
2803
5635
5254
15240
3400
5480
7694
22606
4287

-m 输出传递给main方法的参数，在嵌入式jvm上可能是null

[@5fb59500efa6 ~]$ jps -m
42229 App /opt/src/app/config/zk.json
12317 Jps -m

-l 输出应用程序main class的完整package名或者应用程序的jar文件完整路径名

[@5fb59500efa6 ~]$ jps -l
12371 sun.tools.jps.Jps
42229 com.sohu.sns.reco.App

-v 输出传递给JVM的参数

[@5fb59500efa6 ~]$ jps -v
42229 App -Xms6114m -Xmx6114m -Xmn2200m -Xss256k -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/opt/logs/ -Djava.awt.headless=true -XX:MaxPermSize=512m -Djava.rmi.server.hostname=127.0.0.1 -Dcom.sun.management.jmxremote.port=1099 -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.authenticate=false -Dfile.encoding=UTF-8 -Dmonitor_agent_app_id=184461539_7eb18530-4ea0-11e8-ab05-00163e0f092d -Denv=PRODUCT -Dlogback.configurationFile=/opt/src/config/logback.xml
12414 Jps -Denv.class.path=./:/opt/apps/jdk/lib:/opt/apps/jdk/lib/tools.jar -Dapplication.home=/opt/apps_install/jdk1.7.0 -Xms8m

sun.jvm.hotspot.debugger.DebuggerException: Can’t attach to the process

➜ ~ jinfo 31983
Attaching to process ID 31983, please wait…
Error attaching to process: sun.jvm.hotspot.debugger.DebuggerException: Can’t attach to the process
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: Can’t attach to the process
at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.execute(LinuxDebuggerLocal.java:163) at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.attach(LinuxDebuggerLocal.java:278) at sun.jvm.hotspot.HotSpotAgent.attachDebugger(HotSpotAgent.java:671) at sun.jvm.hotspot.HotSpotAgent.setupDebuggerLinux(HotSpotAgent.java:611) at sun.jvm.hotspot.HotSpotAgent.setupDebugger(HotSpotAgent.java:337) at sun.jvm.hotspot.HotSpotAgent.go(HotSpotAgent.java:304) at sun.jvm.hotspot.HotSpotAgent.attach(HotSpotAgent.java:140) at sun.jvm.hotspot.tools.Tool.start(Tool.java:185) at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118) at sun.jvm.hotspot.tools.JInfo.main(JInfo.java:138) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at sun.tools.jinfo.JInfo.runTool(JInfo.java:108) at sun.tools.jinfo.JInfo.main(JInfo.java:76) Caused by: sun.jvm.hotspot.debugger.DebuggerException: Can’t attach to the process at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.attach0(Native Method) at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.access$100(LinuxDebuggerLocal.java:62)
at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$1AttachTask.doit(LinuxDebuggerLocal.java:269) at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.run(LinuxDebuggerLocal.java:138)

解决办法：

echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope