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--- srun [2014/04/22 16:58]
root created
+++ srun [2021/03/01 11:14] (current)
root
@@ Line 1: / Line 1: @@
 ====== srun ======
-Runs an executable file, not a script (but can “srun /bin/bash ...”).
+Runs an executable file. It is really intended to be used from within **sbatch** scripts. Used within a script, each invocation of **srun** starts a new **job step** (terminology you will see in the slurm documentation).
-Runs the job in the foreground (and blocks unless you use “&”).
+Used from a terminal, srun runs the job in the foreground (and blocks unless you use “&”).
+If you use srun directly (in a login terminal) your job will end if you close your terminal or close your laptop, unless you redirect IO and **disown** the job. You can also use a "terminal multiplexer" like screen, tmux, or byobu. However, even if you take steps to protect against "hang-ups", if the head node needs to be rebooted (to pick up kernel updates, for instance) that will terminate any jobs running through srun. A reboot of the head node will not affect jobs submitted using sbatch.
+==== Examples ====
+srun hostname
+srun --pty bash -i
+  * Runs an interactive shell on a compute node.
+  * You can specify a specific node with -w node5 (for instance).
+    * Will only run if there is a slot available on the node.
+srun -n3 hostname (runs 3 **tasks**: copies of the program specified, may run on the same node)
+srun -n30 hostname (runs 30 **tasks**, will run on multiple nodes since no node in that standard queue has as many as 30 cores)
+srun -N3 hostname (runs on 3 different nodes)
+==== Protecting against "Hang-Ups" ====
+<code>
+srun long-job > srun.out 2>&1 &
+disown
+</code>
+But it's much better to use sbatch.
-Job will end if you close your terminal, unless you redirect IO and **disown** the job.

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