Work Interactively on a Node

Logging in to one of the TACC clusters will place you on a shared login node. These are shared resources and users should not run applications here (including Python, Matlab, R, or any other code downloaded from the internet). Instead, these applications should be run on a compute node.

Determine if You Are on a Login or Compute Node

To determine what type of node you are logged into, use the command hostname. The output of hostname will either show a login node (e.g. login1, login2), or it will show a series of letters and numbers (e.g. nid00015, c001-005) indicating a compute node. The exact output will vary from cluster to cluster. By default, the same information is located at the beginning of the command prompt, as is seen in the next section.

Connect to a Compute Node

To launch an interactive session on a compute node, use the idev command. Below is an example of idev launching from a login node on Lonestar 5 with the default options:

[login]$ idev
 -> Defaults file    : ~/.idevrc
 -> System           : ls5      
 -> Queue            : development   (idev  default       )
 -> Nodes            : 1             (idev  default       )
 -> Tasks per Node   : 24            (~/.idevrc           )
 -> Time (minutes)   : 30            (idev  default       )
 -> Project          : PROJECT-NAME  (~/.idevrc           )

-----------------------------------------------------------------
          Welcome to the Lonestar 5 Supercomputer
-----------------------------------------------------------------

No reservation for this job
--> Verifying valid submit host (login1)...OK
--> Verifying valid jobname...OK
--> Enforcing max jobs per user...OK
--> Verifying availability of your home dir (/home1/01234/username)...OK
--> Verifying availability of your work dir (/work/01234/username)...OK
--> Verifying availability of your scratch dir (/scratch/01234/username)...OK
--> Verifying valid ssh keys...OK
--> Verifying access to desired queue (development)...OK
--> Verifying job request is within current queue limits...OK
--> Checking available allocation (PROJECT-NAME)...OK
Submitted batch job 2573629

 -> After your idev job begins to run, a command prompt will appear,
 -> and you can begin your interactive development session.
 -> We will report the job status every 4 seconds: (PD=pending, R=running).

 ->job status:  PD
 ->job status:  R

 -> Job is now running on masternode= nid00015...OK
 -> Sleeping for 7 seconds...OK    
 -> Checking to make sure your job has initialized an env for you....OK
 -> Creating interactive terminal session (login) on master node nid00015.

[nid00015]$      # note that command prompt has changed

Useful idev Options

You can pass options to idev to control the nature of the interactive job. This includes number of nodes, number of MPI processes, duration of the session, and identity of the queue. For example:

[login]$ idev -N 1 -p development -m 120

The above command will launch a session on one node (-N 1) in the development queue (-p development) for a duration of 120 minutes (-m 120). A full list of idev options can be seen by issuing:

[login]$ idev -h

Connect Multiple Terminals to the Same Interactive Session

It may be useful to have multiple terminals connected to the same interactive session on the same compute node. To do this, first launch a job with idev from one terminal:

Terminal 1

[login]$ idev
...
[nid00015]$

From the command prompt above, you can see the interactive session launched on a compute node with hostname nid00015. From the second terminal, type:

Terminal 2

[login]$ ssh nid00015
...
[nid00015]$

Now both terminals are connected to the same compute node in the interactive session. When the job ends, or when the first terminal disconnects from the compute node, the second terminal will also be disconnected automatically.


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