Login Node¶

Users accessing CCR's HPC resources will be connected to a login node. A login node is a outward facing node within CCR's HPC environment that users can connect to from their local machines. Once on a login node, users can perform a limited number of tasks:

Edit files
Transfer Data
Submitting Jobs
Access storage resources

This page covers connecting to a login node using SSH (Secure Shell Protocol). When you connect via SSH, you authenticate using a private key file on your local machine. For more information about SSH, see Secure Shell on Wikipedia. You can also connect to CCR's login nodes using a web browser with the OnDemand Portal.

Note

Login nodes should not be used for resource-intensive tasks such as running software or compiling code. For those tasks, users should submit batch or interactive jobs to reserve a node in the cluster.

To get started connecting to CCR's HPC clusters and shared storage you need the following:

A CCR user account with two factor authentication enabled and an active allocation to HPC resources. For more information see our getting access guide.
An SSH Key added to your account
An SSH client. Windows users we recommend using Git Bash
An SSH client. Linux & MacOS include a terminal app. For Windows users, we recommend using Git Bash

VPN Required

Access to CCR login nodes is restricted to UB and Roswell Park networks (either on campus or connected to their VPN services). See here

Connecting with SSH¶

Using the SSH protocol, you can connect and authenticate to CCR login nodes. When you set up SSH, you will need to generate a new public/private SSH key pair enabling you to connect to CCR without supplying your username and password. When you connect via SSH, you authenticate using a private key file on your local machine, password authentication is not allowed. To set up SSH, you will need to generate a new SSH key pair and upload the public key to your CCR account using the IDM portal.

Generate new SSH key¶

You can generate a new SSH key pair on your local machine. After you generate the key pair, you can add the public key to your account using CCR's IDM portal. Follow these easy steps:

Open your terminal or Git Bash if you're on windows
Run the following command, substituting in your email address:
```
$ ssh-keygen -t ed25519 -C "your_ub_itname@buffalo.edu"
```
At the prompt, type a secure passphrase
Copy the contents of the public key to your clipboard. The file is located here:
```
~/.ssh/id_ed25519.pub
```
Login to the IDM portal and click on SSH Keys in the left nav menu
Click on the "New SSH Key" button, paste the contents of your public key in the text box, and click "Add".

Logging in¶

To verify you can ssh into the login node, follow these easy steps:

Open your terminal or Git Bash if you're on windows and enter the following:

ssh username@vortex.ccr.buffalo.edu

You may see a warning like this:

The authenticity of host 'vortex.ccr.buffalo.edu (128.205.41.13)' can't be established.
ED25519 key fingerprint is SHA256:PxBS1XqDaspSTQYQj+LHHh4YBSN4XvB7P/VcYGxMR8Y.
Are you sure you want to continue connecting (yes/no/[fingerprint])?

Verify the fingerprint in the message you see matches CCR's public key fingerprint. If it does, then type yes.
You should now be at a shell prompt on the login node:
```
[username@vortex1:~]$
```

First Login - Additional Step

On first login your home directory will be created automatically. You will see a message prompting you to run a script to generate a SSH key pair for use on the cluster and within the OnDemand terminal app. After login, run /util/ccr/sbin/ssh_no_password.sh

Using the SSH Agent¶

Running an SSH agent process on your local machine allows you to load your SSH private key one time and it will be used for every SSH login attempt. This allows you to skip entering your passphrase each time you login. Follow these steps to add your key to the ssh-agent:

Open your terminal or Git Bash if you're on windows

Start the ssh-agent in the background:

$ eval "$(ssh-agent -s)"
> Agent pid 12345

Add your SSH private key to the ssh-agent. If you created your key with a different name use the correct path to your key. You will be prompted to enter your passphrase for the key:
```
$ ssh-add ~/.ssh/id_ed25519
```
List the SSH keys currently loaded in your running SSH agent:
```
$ ssh-add -L
```

OnDemand for Web-Based Cluster Access¶

Open OnDemand provides access to CCR's clusters, storage, visualization servers, and interactive apps. CCR's OnDemand portal offers Linux desktops for GUI-based applications, software applications like MatLab, RStudio Desktop, Jupyter Notebook, and vscode, an interactive development environment. OnDemand can be used in any browser from almost any device. More information about OnDemand can be found here.