When you need to attach process to jmap you might get following error here i have described how we can avoid that.
Run fllowing to get process ID
:jps
3252 Bootstrap
3513 Jps
Then run following to execute jmap
$ jmap -heap:format=b 3252 Attaching to process ID 3252, please wait... Error attaching to process: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process
Then to avoid error run following
$ echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope
Then run again above command
$ jmap -heap:format=b 3252 Attaching to process ID 3252, please wait... Debugger attached successfully. Server compiler detected. JVM version is 17.0-b16 using thread-local object allocation. Parallel GC with 4 thread(s) Heap Configuration: MinHeapFreeRatio = 40 MaxHeapFreeRatio = 70 MaxHeapSize = 1073741824 (1024.0MB) NewSize = 1310720 (1.25MB) MaxNewSize = 17592186044415 MB OldSize = 5439488 (5.1875MB) NewRatio = 2 SurvivorRatio = 8 PermSize = 21757952 (20.75MB) MaxPermSize = 268435456 (256.0MB) Heap Usage: PS Young Generation Eden Space: capacity = 263847936 (251.625MB) used = 226730648 (216.2271957397461MB) free = 37117288 (35.397804260253906MB) 85.93231822742021% used From Space: capacity = 36372480 (34.6875MB) used = 16924568 (16.140525817871094MB) free = 19447912 (18.546974182128906MB) 46.53124560106982% used To Space: capacity = 40763392 (38.875MB) used = 0 (0.0MB) free = 40763392 (38.875MB) 0.0% used PS Old Generation capacity = 333053952 (317.625MB) used = 179019752 (170.7265396118164MB) free = 154034200 (146.8984603881836MB) 53.75097665858053% used PS Perm Generation capacity = 151519232 (144.5MB) used = 93595192 (89.25933074951172MB) free = 57924040 (55.24066925048828MB) 61.771163148451016% used
You will see correct output
文章出处:
http://sanjeewamalalgoda.blogspot.hk/2014/01/how-to-avoid-jmap-error-error-attaching.html