Interactive Cluster Usage
Interactive use of the cluster can take place on the head/login node, but since this node is shared by all users and also supports some of the administrative activities on the cluster, interactive use requiring significant CPU time (more than 1 hour) should take place on a compute node.
Interactive Batch Jobs
An interactive batch job is a process that allows a user to get interactive, command line access to a compute node or nodes. Interactive batch jobs use the same syntax as regular batch jobs, but no job script is specified. All resource requests, etc. are specificed as arguments to the qsub command, and the -I (dash capital i) option is added to specify an interactive batch job. The following command requests an interactive batch job with the default parameters for all resource requests (1 hour of run time on 1 processor):
To request a longer run time or additional nodes, add specific resource requests:
qsub -l nodes=1:ppn=2 -l walltime=4:00:00 -IV
When an interactive batch job is submitted, it is evaluated by the scheduling system to determine if the requested resources are available. The user will see output similar to:
qsub: waiting for job firstname.lastname@example.org to start
When a node is available, the user’s prompt will change to “uniqueID@compute-x-y” to indicate that the job has started on a compute node. When you have finished working on the compute node, type “exit” to end the job and return to the login node.
If no nodes are available, the command will wait until a node is available. If you want to stop waiting and abandon your job request, use the Control-c key combination and then type “y” to confirm that you want to terminate the job.