Scheduled tasks (cron): Difference between revisions

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Created page with " == Using crontab == With crontab you can run jobs on a fixed timeschedule. This means that you can e.g. download some data every day. To start an edit with '''crontab -l'..."
 
IA migration §8: rewrite around scrontab (SLURM cron); discourage login-node crontab; fix crontab -l/-e bug (via update-page on MediaWiki MCP Server)
 
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Recurring, scheduled tasks on Anunna should be run through the scheduler with '''scrontab''', SLURM's built-in cron. scrontab uses the familiar crontab syntax, but runs each scheduled task as a SLURM job on a compute node — so your recurring work gets proper resources and does not load the shared login nodes.


== Using crontab ==
{{Warning|Do not use a plain login-node <code>crontab</code> for recurring work. Anything scheduled with <code>crontab</code> runs on the login node, which is a shared access point not meant for computation, and the crontab is wiped when the login node reboots. Use <code>scrontab</code> instead.}}


With crontab you can run jobs on a fixed timeschedule.
== Using scrontab ==
This means that you can e.g. download some data every day.


To start an edit with '''crontab -l''' , the info on that file can be found by using '''man 5 crontab'''.
Edit your scrontab with:


Be aware of the following :
<syntaxhighlight lang="bash">
scrontab -e
</syntaxhighlight>


The scripts will run on the login node, so do not use a lot of resources
Each entry has two parts: one or more <code>#SCRON</code> lines that set the SLURM options for the job (partition, time limit, resources, job name, …), followed by a normal crontab time specification and the command to run.
The crontab entry will be wiped upon reboot, so if you want to make sure that it is there, it wise to set that up.
 
<syntaxhighlight lang="bash">
#SCRON --partition=main
#SCRON --time=00:10:00
#SCRON --job-name=daily-download
0 2 * * * /home/<group>/<username>/scripts/download.sh
</syntaxhighlight>
 
This runs <code>download.sh</code> as a SLURM job every day at 02:00. List your current entries with:
 
<syntaxhighlight lang="bash">
scrontab -l
</syntaxhighlight>
 
The crontab time format (the <code>0 2 * * *</code> part) is described in the crontab manual page:
 
<syntaxhighlight lang="bash">
man 5 crontab
</syntaxhighlight>
 
== See also ==
* [[Batch Jobs]]
* [[Scheduler Overview (Slurm)]]

Latest revision as of 12:58, 18 June 2026

Recurring, scheduled tasks on Anunna should be run through the scheduler with scrontab, SLURM's built-in cron. scrontab uses the familiar crontab syntax, but runs each scheduled task as a SLURM job on a compute node — so your recurring work gets proper resources and does not load the shared login nodes. 

 ⚠️ Warning: Do not use a plain login-node crontab for recurring work. Anything scheduled with crontab runs on the login node, which is a shared access point not meant for computation, and the crontab is wiped when the login node reboots. Use scrontab instead.

Using scrontab

Edit your scrontab with: 

scrontab -e

Each entry has two parts: one or more #SCRON lines that set the SLURM options for the job (partition, time limit, resources, job name, …), followed by a normal crontab time specification and the command to run. 

#SCRON --partition=main
#SCRON --time=00:10:00
#SCRON --job-name=daily-download
0 2 * * * /home/<group>/<username>/scripts/download.sh

This runs download.sh as a SLURM job every day at 02:00. List your current entries with: 

scrontab -l

The crontab time format (the 0 2 * * * part) is described in the crontab manual page: 

man 5 crontab

See also

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