Helix/Login

Access to bwForCluster Helix is only possible from IP addresses within the BelWü network which connects universities and other scientific institutions in Baden-Württemberg. If your computer is in your University network (e.g. at your office), you should be able to connect to bwForCluster Helix without restrictions. If you are outside the BelWü network (e.g. at home), a VPN (virtual private network) connection to your University network must be established first. Please consult the VPN documentation of your University.

Login nodes are the access points to an HPC system, your $HOME directory and your workspaces. All users must log in to the login nodes to submit jobs to the compute nodes.

Prerequisites for successful login:

You need to have

• completed the 3-step bwForCluster registration procedure.
• set a service password for bwForCluster Helix.
• registered a token for the two factor authentication (2FA).

1 Username

For your username on bwForCluster Helix you need to add a prefix to your local username. For prefixes please refer to the Username Wiki.

Example: If your local username at your University is ab123 and you are a user from Heidelberg University this would combine to: hd_ab123.

2 Hostnames

The system has two login nodes and we use so-called DNS round-robin scheduling to load-balance the incoming connections between the nodes. If you open multiple SSH sessions, these sessions may be established to different login nodes, so processes started in one session might not be visible in other sessions.

Hostname	Node type
helix.bwservices.uni-heidelberg.de	login to one of the two login nodes

3 SSH Clients

For a more detailed information on SSH clients, visit the SSH clients Wiki page.

4 Login from Linux or Mac

Most Unix and Unix-like operating systems like Linux or MacOS come with a built-in SSH client provided by the OpenSSH project.

ssh <username>@helix.bwservices.uni-heidelberg.de
ssh -l <username> helix.bwservices.uni-heidelberg.de

To run graphical applications, you can use the -X or -Y flag to ssh:

ssh -Y -l <username> helix.bwservices.uni-heidelberg.de

5 Login from Windows

For Windows we suggest using MobaXterm for login and file transfer. More recent versions of Windows 10 and Windows 11 using the Windows Subsystem for Linux (WSL) also come with a built-in OpenSSH client. After installing a linux system with WSL use the instructions for linux.

Start MobaXterm, fill in the following fields:

Remote name              : helix.bwservices.uni-heidelberg.de
Specify user name        : <username>
Port                     : 22

After that click on 'ok'. Then a terminal will open where you can enter your credentials.

6 Login Example

To log into bwForCluster Helix, you must provide your service password. Proceed as follows:

1. Use an SSH client as shown above.
2. The system will ask for a one-time password Your OTP:. Please enter your OTP and confirm it with Enter/Return. The OTP is not displayed when typing. If you do not have a second factor yet, please create one (see Registration/2FA).
3. The system will ask you for your service password Password:. Please enter it and confirm it with Enter/Return. The password is not displayed when typing. If you do not have a service password yet or have forgotten it, please create one (see Registration/Password).
4. You will be greeted by the cluster, followed by a shell.

$ ssh -l hd_ab123 helix.bwservices.uni-heidelberg.de
Your OTP:
Password: 

7 Allowed Activities on Login Nodes

To guarantee usability for all the users of clusters you must not run your compute jobs on the login nodes. Compute jobs must be submitted to the queuing system. Any compute job running on the login nodes will be terminated without any notice. Any long-running compilation or any long-running pre- or post-processing of batch jobs must also be submitted to the queuing system.

The login nodes of the bwHPC clusters are the access point to the compute system, your $HOME directory and your workspaces. These nodes are shared with all the users therefore, your activities on the login nodes are limited to primarily set up your batch jobs. Your activities may also be:

• short compilation of your program code and
• short pre- and post-processing of your batch jobs.

We advise users to use interactive jobs for compute and memory intensive tasks like compiling.

8 Password Reset

See Password Guide.

9 De-registration

See De-registration Guide.

10 SSH Keys

In contrast to many other HPC systems it is no longer possible to self-manage your SSH Keys by adding them to the ~/.ssh/authorized_keys file. Existing files will no longer be evaluated. SSH Keys have to be managed via bwServices instead. Please refer to the user guide for this functionality:

• Registering SSH Keys with your Cluster

10.1 Login to bwForCluster Helix

After registration bwForCluster Helix can be accessed via Secure Shell (SSH). Only SSH is allowed for login.

From Linux machines, you can log in using the following command:

ssh <UserID>@helix.bwservices.uni-heidelberg.de

To run graphical applications, you need to enable X11 forwarding with the -X option:

ssh -X <UserID>@helix.bwservices.uni-heidelberg.de

For SSH client programs with graphical user interfaces, fill in UserID and login server name accordingly. For Windows you can use PuTTY or MobaXterm. The later comes with an integrated X11 server which is necessary for the work with graphical applications.

The bwForCluster Helix has serveral login nodes. The selection of the login node is done automatically. If you log in multiple times, different sessions might run on different login nodes. In general, you should use the generic hostname given above to allow us to balance the load over the login nodes.

10.2 Allowed activities on login nodes

The login nodes are the access point to the compute system and to your $HOME directory. The login nodes are shared with all the users of the cluster. Therefore, your activities on the login nodes are limited to primarily set up your batch jobs. Your activities may also be:

• compilation of your program code and
• short pre- and postprocessing of your batch jobs.

To guarantee usability for all the users of the bwForCluster you must not run your compute jobs on the login nodes. Compute jobs must be submitted as Batch Jobs. Any compute job running on the login nodes will be terminated without notice.