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Request an Account

Before you can log in, submit jobs, or even poke around the system, you need a Unity account. Unity is a shared cluster operated by a multi-institutional consortium based at MGHPCC, so the account flow has two parts: you sign in once via your home institution's identity provider, then you join a PI group that grants you compute and storage allocations.

This page walks you through the four steps that take you from "no account" to a working SSH login:

  1. Register on the Unity portal with your Dartmouth NetID.
  2. Join a PI group so you have a place to put your data and run your jobs.
  3. Generate an SSH key through the portal.
  4. Connect from your local machine.

Who can have an account?

Any researcher at a member institution of the Unity consortium can request an account. If you're at Dartmouth, you're eligible. External collaborators not affiliated with a member institution can sometimes get sponsored access through their PI's institution; see the Dartmouth-specific notes after the walkthrough.

What you get

Once your account is qualified (registered + at least one PI group approved), you receive:

  • Login access to Unity's 4 login nodes via SSH at login.unityhpc.org.
  • A home directory at /home/<your_username> (100 GB) for configuration files, scripts, and small personal files.
  • A PI-group work directory at /work/pi_<your_pi_group> (1 TB shared with the group) for research data and job I/O.
  • Scratch space at /scratch (15 TB) for fast temporary work. Files here are not backed up and are auto-purged after a period of inactivity.
  • Access to the Slurm scheduler for submitting work to compute nodes.

For the full storage tour, see Storage Fundamentals.

Step 1: Register on the Unity portal

  1. Browse to https://unity.dartmouth.edu/ and click Login / Request Account in the left sidebar.
  2. In the dropdown, select Dartmouth College and click Continue.
  3. Sign in with your Dartmouth NetID via SSO.
  4. Verify your information and click Register.

You'll start as 'unqualified'

Right after registration, your account is marked unqualified: you can sign into the portal but you can't yet log in to the cluster or submit jobs. You'll qualify in Step 2 by joining a PI group.

Step 2: Join a PI group

Every Unity user must belong to at least one PI (Principal Investigator) group. The PI group determines your storage allocations, scheduler accounting, and which partitions you can run on.

  1. Read the Terms of Service linked above the request button.
  2. Check the box confirming you've read it and click Request to Join a PI Group.
  3. On the My Principal Investigators page, click the + button.
  4. Search for your PI's group (typically named pi_<pi_username>).
  5. Click Send Request.

Your PI receives an email and approves the request. Once approved, your account is qualified and you can log in.

Don't have a specific PI group?

If you aren't yet attached to a particular research group, your institution may run a general-purpose PI group you can join to get started. The Dartmouth-specific notes below tell you which one to search for.

Step 3: Generate an SSH key

Unity uses SSH key authentication, not passwords. The portal generates the key pair for you and registers the public half automatically; you just need to download the private half and put it where your SSH client can find it.

  1. In the left sidebar of the portal, click Account Settings.
  2. Under SSH Keys, click the + button.
  3. Select Generate Key, then choose OpenSSH (macOS/Linux) or PuTTY (Windows).
  4. Download the private key file and click Upload Public Key.

Then move the private key into place on your local machine and load it into your SSH agent:

mv ~/Downloads/privkey.key ~/.ssh/unity-privkey.key
chmod 600 ~/.ssh/unity-privkey.key
ssh-add ~/.ssh/unity-privkey.key

Move-Item ~\Downloads\privkey.key ~\.ssh\unity-privkey.key
ssh-add ~\.ssh\unity-privkey.key

For deeper detail on key management and connection options, see Unity's SSH documentation.

Step 4: Connect

Personalize this page. Enter your NetID and we'll fill it into every copy-pasteable command below. It's saved only in your browser.

Once your key is loaded, connect to the cluster:

ssh your_netid_dartmouth_edu@login.unityhpc.org

Replace your_netid with your actual NetID.

Create a shell alias

Add this to ~/.bashrc or ~/.zshrc so you can simply type unity to connect:

alias unity='ssh your_netid_dartmouth_edu@login.unityhpc.org'

Unity has 4 login nodes. The cluster assigns you to one automatically, but if you want to return to a specific node (for example, to reattach a screen or tmux session), you can SSH directly to login1 through login4 once you've logged in once.

For the full SSH walkthrough including running graphical applications and troubleshooting, see Connecting to the Cluster.

Dartmouth-specific notes

The walkthrough above works for any Unity institution. A few details are specific to Dartmouth:

Username. When you log in via SSH, your username is your NetID with the suffix _dartmouth_edu. For example, if your NetID is f006pfk, your Unity username is f006pfk_dartmouth_edu.

Catch-all PI group. If you don't have a specific research group to join in Step 2, search for pi_general_dartmouth_edu and request to join. Dartmouth maintains this group so any Dartmouth researcher can get started on Unity without waiting on a sponsoring lab.

Storage tiers at Dartmouth. Members of the catch-all group get the free tier:

  • 100 GB home directory
  • Shared access to /scratch for temporary work

If you need the full 1 TB /work allocation or dedicated /project storage, your PI group needs to upgrade to a paid tier. See https://rc.dartmouth.edu/hpc/unity/ for the current pricing and request process.

Non-Dartmouth collaborators

External collaborators need an account through their own institution's Unity portal. If your collaborator's institution is not part of the Unity consortium, they may be able to get an affiliate account at Dartmouth; contact Research Computing and Data for guidance, or see https://unityhpc.org/documentation/getting-access/ for the consortium-wide affiliate process.

Where to ask for help

Managing disk quotas

Every directory you can write to on Unity has a quota, a limit on how much space it can use. Quotas exist to make sure no single user (or runaway program) consumes more than their fair share of a shared resource.

Use df (disk free) to see how much space is left under the quota of any directory you have access to:

df -h ~

Output looks like:

Filesystem      Size  Used Avail Use% Mounted on
vast2:/home      100G   29G   71G  29% /home

If you're running low on space, here are some strategies:

1. Find what's using space. The du command (disk usage) walks a directory and reports per-file or per-subdirectory size:

du -h --max-depth=1 ~ | sort -hr | head -20  # (1)!
  1. This lists the 20 largest directories in your home, sorted by size. It's a quick way to find where space is going.

For an interactive view, ncdu lets you navigate the tree with arrow keys and delete with d:

ncdu ~

2. Remove what you don't need. Old output files, logs from completed jobs, and stale ~/.cache/ entries (especially ~/.cache/huggingface and ~/.cache/pip) are common culprits.

3. Compress files you want to keep but aren't actively using:

gzip large_output.csv           # (1)!
tar -czf old_results.tar.gz old_results/  # (2)!
  1. Compresses a single file in-place. The original is replaced by large_output.csv.gz.
  2. Archives and compresses an entire directory into one file.

4. Move large datasets to a more appropriate storage tier. Your home directory is for small, frequently accessed files. Large research data belongs on /work (shared with your PI group) or /scratch (fast, temporary). See Storage Fundamentals for guidance on choosing the right tier.

Disk quota exceeded

If you see errors like Disk quota exceeded or No space left on device, the filesystem you're writing to is full. Run df -h ~ (or df -h /work/pi_<your_pi_group>) to confirm which quota you've hit, then follow the strategies above to free up space. If you need a temporary workaround to unblock yourself, you can work from /scratch while you clean up.

What's next?

With your account in hand, you're ready to put the cluster to work: