Clarify when batch script runs on pack job

doc/html/heterogeneous_jobs.shtml

@@ -95,9 +95,10 @@ containing the line "#SBATCH packjob" as shown below.</p>
 <pre>
 $ cat new.bash
 #!/bin/bash
-#SBATCH --cpus-per-task=4 --mem-per-cpu=1  --ntasks=128
+#SBATCH --cpus-per-task=4 --mem-per-cpu=16g --ntasks=1
 #SBATCH packjob
-#SBATCH --cpus-per-task=1 --mem-per-cpu=16 --ntasks=1
+#SBATCH --cpus-per-task=2 --mem-per-cpu=1g  --ntasks=8
+
 srun run.app
 
 $ sbatch new.pash
@@ -110,10 +111,14 @@ $ cat my.bash
 #!/bin/bash
 srun run.app
 
-$ sbatch --cpus-per-task=4 --mem-per-cpu=1  --ntasks=128 : \
-         --cpus-per-task=1 --mem-per-cpu=16 --ntasks=1 my.bash
+$ sbatch --cpus-per-task=4 --mem-per-cpu=16g --ntasks=1 : \
+         --cpus-per-task=2 --mem-per-cpu=1g  --ntasks=8 my.bash
 </pre>
 
+<p>The batch script will be executed in the first node in the first component
+of the heterogeneous job. For the above example, that will be the job component
+with 1 task, 4 CPUs and 64 GB of memory (16 GB for each of the 4 CPUs).</p>
+
 <h2><a name="managing">Managing Jobs</a></h2>
 
 <p>Information maintained in Slurm for a heterogeneous job includes:</p>

src/slurmctld/proc_req.c

@@ -3896,13 +3896,18 @@ static void _slurm_rpc_submit_batch_pack_job(slurm_msg_t *msg)
 	if (error_code != SLURM_SUCCESS)
 		goto send_msg;
 
+	/* Create new job allocations */
 	submit_job_list = list_create(NULL);
 	_throttle_start(&active_rpc_cnt);
 	lock_slurmctld(job_write_lock);
 	START_TIMER;	/* Restart after we have locks */
 	iter = list_iterator_create(job_req_list);
 	while ((job_desc_msg = (job_desc_msg_t *) list_next(iter))) {
-		/* Create new job allocation */
+		if (alloc_only && job_desc_msg->script) {
+			info("%s: Pack job %u offset %u has script, being ignord",
+			     __func__, pack_job_id, pack_job_offset);
+			xfree(job_desc_msg->script);
+		}
 		error_code = job_allocate(job_desc_msg,
 					  job_desc_msg->immediate, false,
 					  NULL, alloc_only, uid, &job_ptr,