Connecting to Arrhenius HPC

We will demonstrate different ways to connect to the NAISS Arrhenius high-performance cluster. From the cluster’s point of view, it doesn’t matter which method you use, and you can switch at any time or even use multiple methods simultaneously.

The options are a text-based SSH connection and a graphical remote desktop using ThinLinc, both of which are available on all major operating systems. ThinLinc is useful if you need to view images or documents in GUI programs without first downloading them to your own computer. Because it transfers graphics, it requires a good, stable internet connection.

We show you different methods because some parts of this course require you to view plots and images, and an additional download step would unnecessarily complicate the workflow.

1 SSH connection

Let’s look at the text-based SSH approach first. This type of connection works well even on slow internet connections because it transmits only small amounts of text. You will need a terminal and an SSH client, which are included in most major operating systems:

Linux: use a terminal
macOS: use Terminal
Windows: use PowerShell, Command Prompt, or WSL2

The guide below is based on Arrhenius official instructions.

1.1 Connecting to HPC using SSH

Note

Where username is mentioned, replace it with your cluster username.

Open a terminal and enter the following command:
```
ssh username@login.hpc.arrhenius.naiss.se
```
Enter your password when prompted. As you type, nothing will appear on the screen: no stars and no dots. This is expected. Type the password, press Enter, and then enter your 2FA code.
```
ssh username@login.hpc.arrhenius.naiss.se
(username@login.hpc.arrhenius.naiss.se) Password:
(username@login.hpc.arrhenius.naiss.se) Verification code:
```

Your screen should display a login message and end with a terminal prompt:

Last failed login: Thu Oct  8 20:23:16 CEST 2026 from hxx-xx-xxx-xx.cust.bredband2.com on ssh:notty
There were 2 failed login attempts since the last successful login.
Last login: Thu Oct  8 18:10:47 2026 from hxx-xx-xxx-xx.cust.bredband2.com
Welcome to Arrhenius!

...

[username@arrhenius1 ~]$

Now you are connected to the HPC and can start working.

2 Remote desktop

Note

There are a limited number of ThinLinc licenses, so it’s possible that you might not be able to connect if all licenses are in use. If you are unable to connect, simply try again later.

You can work on the HPC interactively through a graphical user interface (GUI) desktop environment using ThinLinc. This works on all major operating systems ( ).

The Arrhenius ThinLinc server provides a remote desktop on the login nodes. Connect to it using the ThinLinc client by following these steps:

Download and install the ThinLinc client.
Start ThinLinc and enter tl.hpc.arrhenius.naiss.se in the Server field, followed by your username and password. If the client asks for a key instead of a password, click Advanced if necessary, open Options, select the Security tab, and choose Password as the authentication method. Click Connect.
Enter your 2FA code when prompted.
You should now be connected to the remote desktop.
When you have finished using the remote desktop, click your name in the top-right corner of the screen and select Log Out.

For more information, take a look at the official documentation: Arrhenius ThinLinc Guide