Accessing the clusters

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Who can access the HPC clusters

The clusters of ID SIS HPC are open to all members of ETH and external users that have a collaboration with a research group at ETH Zurich. Members of ETH have immediate access to the clusters and can login with their NETHZ credentials. Members of other institutes who have a collaboration with a research group at ETH may use the HPC clusters for the purpose of said collaboration. Their counterpart ("sponsor") at ETH must ask the local IT support group (ISG) of the corresponding department to create a NETHZ guest account for them, including e-mail address and VPN service. Once the NETHZ guest account has been created, they can access the clusters like members of the ETH.

Legal compliance

The HPC clusters of ID SIS HPC are subject to ETH's acceptable use policy for IT resources (Benutzungsordnung für Telematik an der ETH Zürich, BOT). In particular:

  • Accounts are strictly personal.
  • You must not share your account (password, ssh keys) wih anyone else.
  • You must not use someone else's account, with our without their consent.
  • If you suspect that someone used your account, change your password and contact cluster support.

In case of abuse, the offender's account may be blocked temporarily or closed. System administrators are obliged by law to investigate abusive or illegal activities and report them to the relevant authorities.


Access to the HPC clusters of ID SIS HPC is only possible via secure protocols ( ssh, sftp, scp, rsync). The HPC clusters are only accessible from inside the ETH network. If you would like to connect from a computer, which is not inside the ETH network, then you would need to establish a VPN connection first. Outgoing connections to computers inside the ETH network are not blocked. If you would like to connect to an external service, then please use the ETH proxy service:

First login

On your first login, you need to accept the cluster's usage rules. Afterwards your account is created automatically. Please find below the user agreement for the Euler cluster as an example:

Please note that the Euler cluster is subject to the "Acceptable Use Policy
for Telematics Resources" ("Benutzungsordnung fuer Telematik", BOT) of ETH
Zurich and relevant documents (, in particular:

  * your Euler account (like your NETHZ account) is *strictly personal*
  * you are responsible for all activities done under your account
  * you must keep your password secure and may not give it to a 3rd party
  * you may not share your account with anyone, including your supervisor
  * you may not use someone else's account, with or without their consent
  * you must comply with all civil and criminal laws (copyright, privacy,
    data protection, etc.)
  * any violation of these rules and policies may lead to administrative
    and/or legal measures

Before you can proceed you must confirm that you have read, understood,
and agree to the rules and policies mentioned above.


You can connect to the HPC clusters via the SSH protocol. For this purpose it is required that you have an SSH client installed. The information required to connect to an HPC cluster, is the hostname of the cluster that you would like to connect to and your NETHZ credentials (username, password).

Cluster Hostname

Linux, Mac OS X

Open a shell (Terminal in OS X) and use the standard ssh command

ssh username@hostname

where username is your NETHZ username and the hostname can be found in the table shown above. If for instance user leonhard would like to access the Euler cluster, then this would look like

leonhard@calculus:~$ ssh's password: 
Last login: Fri Sep 17 14:17:54 1783 from

      ____________________   ___
     /  ________   ___   /__/  /
    /  _____/  /  /  /  ___   /
   /_______/  /__/  /__/  /__/
   Eidgenoessische Technische Hochschule Zuerich
   Swiss Federal Institute of Technology Zurich
                                        E U L E R  C L U S T E R    CentOS 6

                                NEW! -->

[leonhard@euler04 ~]$


Since Windows does not provide an ssh client as part of the operating system, users need to download a third-party software in order to be able to establish ssh connections.

Widely used ssh clients are for instance PuTTY and Cygwin.


If you use PuTTY, then it is sufficient to specify the hostname of the cluster that you would like to access and to click on the Open button. Afterwards, the users will be prompted to enter their NETHZ credentials. When using Cygwin, then you can enter the same command as Linux and Mac OS X users.

 ssh username@hostname

SSH keys

ssh keys allow you to login to a cluster without having to type a password. This can be useful for file transfer and automated tasks. When you use ssh keys properly, then this is much safer than passwords. There are always pairs of keys, a private (sotred on your local workstation) and a public (stored on the computer you want to connect to). You can generate as many key pairs as you want. In order to make the keys even more secure, you should protect them with a passphrase.

On your workstation, use ssh-keygen to generate a key pair. By default the private key is stored as $HOME/.ssh/id_rsa and the public key as $HOME/.ssh/ In order to setup passwordless access to a cluster, copy the public key to the .ssh directory on the cluster (for this example, we use the Euler cluster).

cat $HOME/.ssh/ | ssh "cat - >> .ssh/authorized_keys"

Some Linux distributions provide tools for copying keys.


The clusters of ID SIS HPC use the X window System (X11) to display a program's graphical user interface (GUI) on a users workstation. You need to install an X11 server on your workstation to siplay X11 windows. The ports used by X11 are blocked by the cluster's firewall. To circumvent this problem, you must open an SSH tunnel and redirect all X11 communication through that tunnel.


Xorg (X11) is normally installed by default as part of most Linux distributions. If you are using a version newer than 1.16, then please have a look at the troubleshooting section at the bottom of this wiki page.

ssh -Y username@hostname

Mac OS X

Since X11 is no longer included in OS X, you must install XQuartz. If you are using a version newer than 2.7.8, then please have a look at the troubleshooting section at the bottom of this wiki page.

ssh -Y username@hostname


X11 is not supported by Windows. Users need to install a third-party application in order to use X11 forwarding. Widely used X11 servers are for instance Cygwin/X, Xming.


When connecting from outside of the ETH network to one of the HPC clusters of ID SIS HPC, one first needs to establish a VPN connection. A VPN client can be downloaded from The VPN client is configured to connect to the ETH network.



Permission denied

If you enter 3 times a wrong password, then you will get a permission denied error:

leonhard@calculus:~$ ssh's password: 
Permission denied, please try again.'s password: 
Permission denied, please try again.'s password: 
Permission denied (publickey,password,hostbased).

In case you receive a "Permission denied" error, please check if you entered the correct password. If you think that your account has been corrupted, then please contact the service desk of IT services of ETH Zurich.

If you enter a wrong password too many times or in a high frequency, then we might block access to the clusters for your account, because it could be correupted. If you account has been blocked by the HPC group, then please contact cluster support.


If you try to login and receive a timeout error, then it is very likely that you tried to connect from outside of the ETH network to one of the HPC clusters.

leonhard@calculus:~$ ssh -Y
ssh: connect to host port 22: Connection timed out

Please either connect from the inside of the ETH network, or establish a VPN connection.

Indirect GLX rendering error

When using an SSH connection with X11 forwarding enabled, newer versions of the Xorg server show an error message, when the graphical user interface of an application is started:

X Error of failed request: BadValue (integer parameter out of range for operation)
  Major opcode of failed request: 153 (GLX)
  Minor opcode of failed request: 3 (X_GLXCreateContext)
  Value in failed request: 0x0
  Serial number of failed request: 27
  Current serial number in output stream: 30

This error is cause by starting your X11 server without enabling the setting for indirect GLX rendering (iglx), that is required for X11 forwarding. Up to version 1.16 of the Xorg server, the setting iglx, has been enabled by default. With version 1.17, the default has changed from +iglx to -iglx. Now the setting needs to be enabled either in the Xorg configuration file or with a command line setting, when starting the Xorg server manually. For Xquartz versions up to 2.7.8, the iglx setting is enabled by default. If you would like to use XQuartz 2.7.9 or newer, then please make sure that you enable the iglx setting when the X-server is started.

This problem is described in the following article:

Please find below some links, which address the problem for specific operating systems.

Operating system Link
Red Hat Enterprise Linux (RHEL)
Mac OS X