Table of Contents

Accessing the Cluster

Caviness currently features two login nodes through which users interact with the cluster. The host name caviness.hpc.udel.edu will connect you to one of those two nodes1). For example, from a terminal window on a Mac or Linux client:

localhost$ ssh «username»@caviness.hpc.udel.edu
    :
[«username»@login01 ~]$

The default shell prompt on Caviness displays the name of the login node. If a user must connect to a specific login node, use that node's full domain name:

localhost$ ssh «username»@login00.caviness.hpc.udel.edu
    :
[«username»@login00 ~]$

When reporting connection problems, please include the -vvv flag in your ssh command to produce verbose output and include that output in your help ticket.

Do not run the ssh-keygen command on Caviness. This command can destroy your account's ability to login to compute nodes without requesting a password. If you do this by mistake, you can either:

Workgroups

Each entity that invests in the Caviness cluster is given a workgroup which encompasses sponsored user accounts, on-cluster storage, and purchased compute resources. The workgroup name (referenced as «workgroup» in this documentation) can refer to

The default workgroup for all users is everyone; this workgroup has no Slurm partitions available to it and no shared storage space. To change your shell to a specific workgroup, use the workgroup command:

[«username»@login00 ~]$ workgroup -g «workgroup»
[(«workgroup»:«username»)@login00 ~]$

The workgroup command is often the first command you will issue after logging-in to the cluster, since it prepares the shell for work within a specific workgroup context2).

Workgroups can create a $WORKDIR/sw/bin directory and add executables to it. If that directory exists, it is automatically prepended to a sponsored user's $PATH when using the workgroup command to enter that workgroup.

Thereafter, the exit command will return you to your original login shell:

[(«workgroup»:«username»)@login00 ~]$ exit
[«username»@login00 ~]$

Workgroup queries

The workgroup command also allows you to query to which workgroups you belong:

[«username»@login00 ~]$ workgroup --query workgroups
 1001  workgroup1
 1010  workgroup10

All available options are summarized using the workgroup –help command.

Shell customization

Alteration of your .bashrc and .bash_profile files is strongly discouraged. Adding directories to the PATH, LD_LIBRARY_PATH, and PYTHONPATH environment variables is best done using VALET packages and not by adding code to your .bashrc file. Keeping .bashrc and .bash_profile as close to pristine as possible often prevents difficult-to-debug problems from occurring when running jobs on the cluster.

The .bash_udit file in your home directory controls shell customizations offered by UD IT:

VariableDescription
IT_WANT_ENV_EXTENSIONSSet to yes to enable the effects of the other variables
IT_SET_WORKGROUP_ON_LOGINSet to yes to automatically change to your default workgroup at login
IT_DEFAULT_WORKGROUPThe name of the workgroup to use by default; if unspecified, then the first workgroup listed by the workgroup –query workgroups command
IT_WORKGROUP_CHDIRChange to the workgroup's $WORKDIR by default

For example, if the user edits .bash_udit to set:

IT_WANT_ENV_EXTENSIONS="yes"
IT_DEFAULT_WORKGROUP="«workgroup»"
IT_WORKGROUP_CHDIR="yes"
IT_SET_WORKGROUP_ON_LOGIN="no"

then the shell and workgroup command will behave as follows:

localhost$ ssh «username»@caviness.hpc.udel.edu
    :
[«username»@login01 ~]$ workgroup
WARNING:  Your working directory has been changed to /work/«workgroup»

[(«workgroup»:«username»)@login01 «workgroup»]$

All additional adjustments to the shell environment should be handled using VALET.

1)
Round-robin DNS load balancing returns multiple IP addresses when the name caviness.hpc.udel.edu is looked-up, in random order. Your SSH client will use the first IP address returned.
2)
The workgroup's VALET package definitions will become available to you, and the $WORKDIR environment variable will point to the shared storage. Also, the Slurm sbatch/srun/salloc commands will default to using the «workgroup» account for job submission.