Understanding Intel® Cluster Checker Debug Output and the Secure Shell (SSH)

Intel® Cluster Checker can provide detailed debug output. Debug mode can be enabled either through use of the --debug command line option for all checks, or on a per-check basis using the <debug/> element tag. Debug output is provided in one or more files named using the format <module_name>-<timestamp>.debug.

Most checks verify operations on the compute nodes. In these instances, the node running cluster-check executes a command through SSH to the compute node. The debug output for these modules may appear truncated, because the output in the debug file does not include the SSH command itself.

This is by design. Intel Cluster Checker debug output shows only the command executed by the compute node. To improve readability of debug files, the complete SSH command executed on the head node is not provided.
The command issued over SSH from the head node to a compute node uses the following format:

ssh -T -o BatchMode=yes -o ForwardX11=no -q -o StrictHostKeyChecking=no <compute_node> <remote_command>


Correct function of this SSH command line is verified by the ssh module before any other modules are attempted. At this time, it is not possible to enable complete output of all commands executed on the head node, or to change SSH command line parameters.

Example

The single_authentication module verifies that every compute node can SSH to every other compute node. Enable debug output for this module using the <debug/> configuration tag:

<single_authentication>
<debug/>
</single_authentication>


Debug output will appear as:

*** compute-0-0 ***
ssh -q compute-0-1 echo "test string"

*** compute-0-1 ***
ssh -q compute-0-0 echo "test string"


However, the actual command lines executed on the head node are:

ssh -T -o BatchMode=yes -o ForwardX11=no -q -o StrictHostKeyChecking=no compute-0-0 ssh -q compute-0-1 echo "test string"

ssh -T -o BatchMode=yes -o ForwardX11=no -q -o StrictHostKeyChecking=no compute-0-1 ssh -q compute-0-0 echo "test string"


Both of these commands consist of two parts:

  1. The command issued over SSH from the head node to a compute node:
    ssh -T -o BatchMode=yes -o ForwardX11=no -q -o StrictHostKeyChecking=no compute-0-1
  2. The remote command executed on the compute node; in this case, SSH from one compute node to another compute node:
    ssh -q compute-0-0 echo "test string"

Only the remote command is included in debug output.

Per informazioni più dettagliate sulle ottimizzazioni basate su compilatore, vedere il nostro Avviso sull'ottimizzazione.