SESYNC’s Slurm compute cluster allows users to run big memory- and processor-intensive jobs. Many users don’t know that you can access the memory and processing power of the cluster interactively, typing commands directly into the command line or into an R or Python session. This FAQ briefly describes how to start an interactive job on the Slurm cluster.
First, you need to open a terminal window and connect to the SSH server. On Windows machines, if you want to use applications with a graphical interface (such as displaying R plots in real time), you will need to use a third-party client such as PuTTY or MobaXTerm. See this FAQ on accessing Linux resources for help on getting the client set up.
Log into the server by typing
ssh (your username goes here)@ssh.sesync.org
into the terminal prompt, and then entering your password when prompted.
Next, start an interactive job. This is done with the shell command
salloc, which requests an allocation of one or more cluster nodes. A typical interactive job request could be as simple as:
salloc -n 1
-n 1 means you are requesting one node. You can add other options such as
--partition=sesyncshared or request specific amounts of memory or time. See the Slurm documentation page for salloc or the SESYNC cluster Quickstart page for more information — the available options for
salloc are mostly the same as for
If the node(s) you requested are available you will get a message like
salloc: Granted job allocation 363010
and you will get another terminal prompt. Your interactive job is now running!
Now that your interactive job has started, you can do things like start an R session from the command line. This is as easy as typing
R but it is often preferable to type
R --no-save --no-restore
That will ensure that your R workspace will not automatically save to your working directory and clutter things up in case your job terminates abruptly.
You can now run R code from the command line, including code that runs in parallel if you want. If you run code to draw and view a plot, the display will be forwarded from the remote machine to a window on your local machine. (This can be sluggish sometimes so it is often better to write the plot to a file and view it later.)
Once you are done with your job, quit R using
q() (or quit whatever other application you are running). Then type
into the command prompt. You will see a message like
salloc: Relinquishing job allocation 363010
to indicate that the nodes you ran your job on are now freed up for other users.