求助：PBSpro中$PBS_NODEFILE变量为空问题

Hey there, sorry to hear you're stuck with this frustrating issue—having an empty $PBS_NODEFILE even after requesting multiple nodes can really derail your workflow. Let's break down the most likely causes and fixes to get this sorted:

1. Double-Check Your Job Submission Command #

First, make sure you're requesting multiple nodes correctly in your qsub command. PBS Pro uses the select resource specification to define node counts, and skipping this (or using incorrect syntax) can lead to unexpected node allocations (and an empty node file).

A valid multi-node request looks like this (example for 2 nodes with 4 CPUs each):

qsub -l select=2:ncpus=4 your_job_script.sh

• Avoid using outdated syntax like -l nodes=2 unless your cluster specifically supports it—modern PBS Pro relies on select for node-level resource requests.
• Also, check your job script to ensure you aren't accidentally unsetting or overwriting $PBS_NODEFILE somewhere (e.g., an unset PBS_NODEFILE line that slipped in).

2. Verify Your Job's Actual Node Allocation #

Sometimes the issue isn't with the node file itself, but that your job wasn't actually allocated multiple nodes. Use qstat -f <your_job_id> to inspect the job details:

• Look for the exec_host field: it should list all nodes assigned to your job (separated by commas). If only one node appears here, your resource request didn't work as intended.
• Check the Resource_List.select field to confirm the number of nodes PBS interpreted from your submission command.

3. Check Cluster Permissions and Configuration #

If your resource request looks correct but you're still getting a single node, reach out to your cluster administrator to rule out these possibilities:

• Your user account might not have permissions to submit multi-node jobs.
• The queue you're submitting to could have limits on maximum node count per job.
• There might be a cluster-wide PBS Pro configuration that disables automatic $PBS_NODEFILE generation for certain job types.

4. Manual Node File Workaround #

If all checks pass but $PBS_NODEFILE is still empty, you can manually generate a node list using other PBS environment variables or commands:

# Option 1: Extract nodes from $PBS_EXECHOST
echo $PBS_EXECHOST | tr ',' '\n' > custom_nodefile

# Option 2: Pull node info via qstat
qstat -f $PBS_JOBID | grep exec_host | awk -F= '{print $2}' | tr ',' '\n' > custom_nodefile

You can then use custom_nodefile in your script wherever you'd normally use $PBS_NODEFILE.

5. Check PBS Pro Version Compatibility #

Older versions of PBS Pro had occasional bugs where $PBS_NODEFILE wouldn't populate correctly for multi-node jobs. If your cluster is running an outdated version, ask your admin if upgrading to a newer release (e.g., 20.x or later) might resolve the issue.

内容的提问来源于stack exchange，提问作者Jurgen Strydom