Delta Login Methods

Note

If you don’t have an allocation on Delta, go to Delta Allocations to learn how to submit an allocation request.

Once you have a Delta allocation, the primary methods for logging into Delta are:

Direct Access Login Nodes - Most common login method for users.
Open OnDemand - Simplest login method; uses a web browser. Good for verifying that your account is working.
VS Code

Direct Access Login Nodes

Direct access to the Delta login nodes is via SSH using your NCSA username, password, and NCSA Duo MFA. The login nodes provide access to the CPU and GPU resources on Delta. See the NCSA Allocation and Account Management page for links to NCSA Identity and NCSA Duo services.

ACCESS awarded projects - Your NCSA username is in your ACCESS Profile; once logged in, scroll to the bottom of the page to the “Resource Provider Site Usernames” table. If you don’t know your NCSA username, submit a support request for assistance.

Login Node Hostnames

Warning

In January 2024, Delta was upgraded to Slingshot11. Please use the round robin login, login.delta.ncsa.illinois.edu, to SSH into the system. For single host SSH, use dt-login01.delta.ncsa.illinois.edu, dt-login02.delta.ncsa.illinois.edu, or dt-login03.delta.ncsa.illinois.edu. See the ACCESS Delta Notice: Delta maintenance 01-23-2024 - 01-25-2024 for more details.

Login Node Hostnames
Login Node Hostname	Description
login.delta.ncsa.illinois.edu	Preferred hostname. Alias that round-robin logs in to one of Delta login nodes.
dt-login.delta.ncsa.illinois.edu	Alias that round-robin logs in to one of the Delta login nodes.
`dt-login[01-04].delta.ncsa.illinois.edu`	There are four Delta login nodes, `dt-login01`, `dt-login02`, `dt-login03`, and `dt-login04`.

SSH Examples

In the examples below, replace username with your Delta login username.

Round robin log into a login node
```
ssh [email protected]
```
-l username is an alternative syntax for <user>@<host>
```
ssh -l username login.delta.ncsa.illinois.edu
```
-Y allows X11 forwarding from Linux hosts
```
ssh -Y [email protected]
```

Use of SSH key pairs is disabled for general use. This means that most individual users, even principal investigators (PIs), are not allowed to use SSH key pairs to log in instead of 2-factor authentication.

The one exception is: if you are the PI of a Gateway allocation (this is not most projects), then please submit a support request to get the Gateway account’s key pairs set up.

Login Node Limits

To keep the login nodes responsive and usable by all, limits on effective CPU-core use and memory by user on a node are enabled through Linux cgroups.

Currently, the effective CPU-core utilization is limited to 16 cores although the actual CPU-core count is not limited. This means that installers that look at the number of CPUs will see 128 cores, while actual effective use will be limited to 16 cores by an individual user (not per shell or per process).

To prevent the login nodes from running out of memory, and please note that login nodes do not have swap enabled, the memory cgroup settings are 37G (15% of total memory) for High and 62G (25% of total memory) for Max memory use by an individual user (not per shell or per process).

Maintaining Persistent Login Sessions: tmux

The tmux utility is available on login nodes to maintain persistent login shells. This is a great technique to keep your shell alive for days and between network disconnects.

After making note of the hostname, use the targeted login hostnames (dt-login01, dt-login02, dt-login03, or dt-login04) to attach to the login node where you started tmux. Avoid the round-robin hostname when using tmux.

See the tmux man page for more information.

SSH Keyboard-Interactive

For command line SSH clients, use the following settings if you have trouble logging in to Delta:

ssh -o PreferredAuthentications=keyboard-interactive,password

Open OnDemand

With Open OnDemand (OOD), you can access Delta, in a web browser! Go to Open OnDemand on Delta for more topics including:

Shell interface.

Interactive apps: Jupyter Lab, Code Server (VS Code), TensorBoard, and Desktop (virtual Linux desktop).

Jupyter Lab customization for Anaconda Environments and R.

How to Log Into the Delta OOD Dashboard

Navigate to the Open OnDemand dashboard.
Log in through CILogon with your NCSA username, password, and Duo MFA.
Once logged in, navigate the dashboard using the menu bar at the top of the window.

VS Code

Refer to Visual Studio Code, Remote - SSH