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Administration Guide


Diagnosing problems with Distributed Command Execution Manager

DCEM uses IBM Cluster Systems Management (CSM), which, in turn, uses several other tools. Understanding this relationship can be helpful in diagnosing problems.

Problems due to insufficient setup of underlying subsystems

The underlying CSM uses the Resource Monitoring and Control (RMC) subsystem to monitor and communicate with all nodes. If you are experiencing problems communicating with managed nodes, verify that RMC is running on each node, and that the security access and control list (ACL) file has been set up to allow the nodes to communicate with the management server.

DCEM uses the CSM dsh command to run commands on the nodes. In order for the dsh command to work, security needs to be set up on each node in such a way that dsh is allowed to run commands on that node. The security setup is dependent upon the type of remote shell you are using. The default remote shell is rsh, and to set up security on each node to allow dsh to run commands on that node (using rsh), you must add the management server host name to the /.rhosts file on the nodes that will be managed nodes. For example, if you want to run commands as root on machine2 from machine1, to the /.rhosts file on machine2, you would have to add the line machine1 root.

To verify the successful installation of CSM, list the active nodes by running the lsnode -p command and verify that dsh is working by running the dsh -a date command. For information, see IBM CSM for Linux: Software Planning and Installation Guide.

Interactive commands and GUI applications

The CSM dsh command does not support the execution of interactive commands. Therefore, attempting to run an interactive command (one that requires input from standard in) from DCEM will not work.

To run an XWindows GUI application from DCEM, make sure that the DISPLAY variable is first set to your system's DISPLAY address, so that the GUI will display on your system. (For example, in the General panel, command area, you could first export the DISPLAY variable to your display's address prior to issuing your command name.) If you run a GUI application correctly from DCEM, the application will remain in the "Working" state until you choose to exit the GUI.

Security considerations and remote shells

DCEM takes in the same underlying security considerations as the CSM dsh command. You can use any underlying remote shell, but it is the system administrator's responsibility to configure and enable remote shell access. DCEM uses the CSM dsh command, which uses the underlying rsh security protocol by default. For more information about security considerations for dsh and preparing for dsh and configuring the remote shell, see the IBM CSM for Linux: Software Planning and Installation Guide.

Diagnostic information

All DCEM command activity of failures and successes are saved in log files to use later if you have to diagnose problems. These log files are stored in the following directory:

home/dcem/log/log file name

To see more detail on the actual underlying CSM command execution string specified as a result of running your created command specification, run the Perl script (outside of DCEM) in debug mode and directly from your AIX command line, as follows:

<commandSpecificationName>.pl -debug


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