使用Java监控工具出现 Can't attach to the process
使用Java监控工具出现 Can't attach to the process
问题重现
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➜ jinfo -flags 3032
Attaching to process ID 3032, 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:483)
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)
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解决办法
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echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope
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再次执行时就可以得到结果了
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➜ jinfo -flags 3032
Attaching to process ID 3032, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.5-b02
Non-default VM flags: -XX:InitialHeapSize=41943040 -XX:MaxHeapSize=536870912 -XX:MaxNewSize=178782208 -XX:MinHeapDeltaBytes=524288 -XX:NewSize=1572864 -XX:OldSize=40370176 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseParallelGC
Command line: -Dosgi.requiredJavaVersion=1.6 -XX:MaxPermSize=256m -Xms40m -Xmx512m
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原因
这是因为新版的Linux系统加入了 ptrace-scope 机制. 这种机制为了防止用户访问当前正在运行的进程的内存和状态, 而一些调试软件本身就是利用 ptrace 来进行获取某进程的内存状态的(包括GDB),所以在新版本的Linux系统, 默认情况下不允许再访问了. 可以临时开启. 如:
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echo 0 > /proc/sys/kernel/yama/ptrace_scope
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永久写到文件来持久化:
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emacs /etc/sysctl.d/10-ptrace.conf
添加或修改为以下这一句:(0:允许, 1:不允许)
kernel.yama.ptrace_scope = 0
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