【問題一】已安裝JDK，可以正常執行jstat，但是執行jmap時提示：bash: jamp: command not found

解決方案：

1、echo $JAVA_HOME，檢視JDK安裝路徑

[[email protected] bin]# echo $JAVA_HOME
/opt/jdk

2、cd /opt/jdk/bin，切換到bin目錄

[[email protected] bin]# cd /opt/jdk/bin

3、./jmap -dump:file=/data/logs/jmap/auto.dump PID，dump記憶體分析日誌

[[email protected]
 
 bin]# ./jmap -dump:file=/data/logs/jmap/auto.dump 13
13: Unable to open socket file: target process not responding or HotSpot VM not loaded
The -F option can be used when the target process is not responding
[[email protected] bin]# ./jmap -F -dump:file=/data/logs/jmap/auto.dump 13
Attaching to process ID 13, please wait...
Error attaching to process: sun.jvm.hotspot.debugger.DebuggerException: cannot open binary file
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: cannot open binary file
        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.HeapDumper.main(HeapDumper.java:83)
        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.jmap.JMap.runTool(JMap.java:201)
        at sun.tools.jmap.JMap.main(JMap.java:130)
Caused by: sun.jvm.hotspot.debugger.DebuggerException: cannot open binary file
        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)
 

【問題二】Ubuntu 系統，執行./jmap -F -dump:file=/data/logs/jmap/auto.dump PID報錯，提示：Error attaching to process: sun.jvm.hotspot.debugger.DebuggerException: cannot open binary file

解決方案：

（1）方法一

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

該方法在下次重啟前有效。 

（2）方法二

永久有效方法 
sudo vi /etc/sysctl.d/10-ptrace.conf 
編輯下面這行: 
kernel.yama.ptrace_scope = 1 
修改為: 
kernel.yama.ptrace_scope = 0 
重啟系統，使修改生效。 
該bug詳細資訊請參考官方文件: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7050524

[[email protected] bin]# ./jmap -F -dump:file=/data/logs/auto.dump 14
Attaching to process ID 14, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.121-b13
Dumping heap to /data/logs/auto.dump ...

【問題三】記憶體日誌分析

上傳檔案：只需在shell終端模擬器中輸入命令“rz”，即可從彈出的對話方塊中選擇本地磁碟上的檔案，利用Zmodem上傳到伺服器當前路徑下。
下載檔案：只需在shell終端模擬器中輸入命令“sz 檔名”，即可利用Zmodem將檔案下載到本地某目錄下。