Please, find the debuggerattach.jar file in the attachments.

Starting from the build ea/124 the jcmd command is not able to recognize some java processes.

1) Run the following command in one Terminal:

% /java/re/jdk/9/promoted/latest/binaries/linux-x64/bin/java -cp debuggerattach.jar -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5900
Listening for transport dt_socket at address: 5900

2) In another terminal:

% ps -ef | g debuggerattach
sspitsyn 28995 28282 0 14:20 pts/0 00:00:00 /java/re/jdk/9/promoted/latest/binaries/linux-x64/bin/java -cp debuggerattach.jar -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5900

The process 28995 is not recognized by the jcmd tool:

The command 'jcmd 28995 VM.version' can't find the process 28995:
  % /java/re/jdk/9/promoted/latest/binaries/linux-x64/bin/jcmd 28995 VM.version
  Could not find any processes matching : '28995'

However, the build ea/123 successfully finds the process:
  % /java/re/jdk/9/promoted/ea/123/binaries/linux-x64/bin/jcmd 28995 VM.version
  28995:
  Java HotSpot(TM) 64-Bit Server VM version 9-ea+160
  JDK 9.0.0

It seems the regression was introduced by the build ea/124:
  % /java/re/jdk/9/promoted/ea/124/binaries/linux-x64/bin/jcmd 28995 VM.version
  Could not find any processes matching : '28995'