When running a one-off job or developing a PBS script, it is convenient to be able to run commands directly inside the PBS environment.
Interactive PBS sessions can be started using
qsub with the
-I option. By default, interactive sessions are allocated a single CPU and an amount of RAM that varies by system (900MB on sequoia and 1GB on catalpa). If you need more resources than than the default, you can request them. For instance, to request four CPUs and five GB of RAM, you would run:
qsub -I -lncpus=4 -lmem=5gb
Once you have started an interactive job, PBS will place you on a node with the required resources. You may then run your program as you normally would.
If you program uses more resources than it requested, PBS will kill your job to protect other users’ well-behaving jobs.
When you’re done with your interactive job, exit your shell as you normally would to end the job and return to the head node. With the
Control-D will work.