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:

• recover an older copy of ~/.ssh from your home directory's ZFS snapshots
• execute mv ~/.ssh ~/.ssh.bak, logout and log in to Caviness again (the system will generate a new key pair for you)

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 Unix group to which all sponsored user accounts are members
• The shared storage allocated to the workgroup
• The Slurm:
  • Account to which jobs are submitted
  • Partition which grants priority-access to purchased compute resources

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⁾.

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

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

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.

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:

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.