Access and Login to the Linux-Cluster

How to get an Account

Please see article Compact Guide to first-time Linux Cluster Access Process.

How to apply for a Linux Cluster project

Login and Security

Only the login nodes can be accessed interactively from the outside world. Two mechanisms are provided for logging in to the system; both incorporate security features to prevent appropriation of sensitive information by a third party.

Access via Secure Shell to Login Nodes

Details on how to configure ssh for usage with the LRZ clusters are available in the document ssh - Secure Shell on LRZ HPC Systems.

From the UNIX command line on the own workstation the login to an LRZ account xyyyyzz is performed via the following command:

ssh -Y cool.hpc.lrz.de -l xxyyyzz

Please note, that this is a Round Robin address. You will be forwarded to one of the Linux Cluster login nodes!

Remarks on ssh access:

  • The -Y option of ssh is responsible for tunneling of the X11 protocol, it may be omitted if no X11 clients are required, or if you already have otherwise configured X11 tunnelling in your ssh client.

  • After successful login you will find yourself in the HOME directory on the Linux Cluster. This is a DSS volume, which is uniformly mounted on all cluster nodes.

Two-Factor Authentication

Please refer to Two-Factor Authentication on the Linux Cluster

Usage Policy on Login Nodes

The login nodes are meant for management tasks, such as:

  • preparing your jobs,
  • developing your programs, e.g. compile codes,
  • a gateway for copying data from your own computer to the cluster and back again.

Since this resource is shared among many users, LRZ demands that you do not start any

  • long-running,
  • memory-hogging or
  • parallelized programs

on these nodes! Production runs should use batch jobs (serial or parallel) that are submitted to the SLURM scheduler. Our SLURM configuration also supports semi-interactive testing.

Violation of the usage restrictions on the login nodes may lead to your account being blocked from further access to the cluster, apart from your processes being forcibly removed by LRZ administrative staff!

Changing of Password and Shell

Please always use the web interface on the LRZ server to change your login password or your login shell for the cluster systems. Cluster-local commands cannot be used for this purpose.

Please note the LRZ policy for the selection and use of passwords:

Changing the password is necessary after it has been newly issued, or reset to a starting value by a master user or LRZ staff. This assures that actual authentication is done with a password known only to the account owner.

Support via Service Desk

Questions concerning the usage of the Linux Cluster should always be directed to the LRZ Servicedesk. A member of the LRZ HPC support team will then attend to your needs.

Documentation for Application Software and Packages

Please start from the HPC Software and Programming Support entries on the LRZ web server.


LRZ-specific configuration and policies on the clusters

Moving data from/to the cluster

The preferred method to move data to/from LRZ's Linux Cluster is using the Globus Research Data Management Portal. Details on the usage of Globus can be found here. Alternatively, you can also use scp (Secure Copy) or grid-ftp. FTP access to the cluster from outside (and also within the clusters) is disabled for security reasons. 

User accounts are personalized

User accounts are always assigned to a particular person. For a number of reasons, sharing of user accounts between different persons is not permitted; if noticed, it will lead to the account being deactivated by LRZ. All involved parties (including the Master User of the account's project) will be notified with information on the measures needed to rectify the situation.

Firewall, networking

The cluster is protected from certain types of external attacks by a firewall, the configuration of which may impact the functionality of certain applications as described in the following.

X11 Protocol

Direct X11 connections (via xhost or xauth) are prohibited, only ssh tunneling is supported.

Routing

None of the batch nodes in the cluster are by default routed to the outside world. Please contact LRZ Servicedesk if you require a particular system to be routed to the batch nodes.

Electronic mail

We recommend against using the Linux Cluster for mail purposes (apart from having the batch scheduler send mails to you, occasionally).

Environment

Environment settings are controlled via the LRZ module system. Such settings are needed to access specific application program packages, or to properly establish a development enviornment.

Using the cron or at commands

This is not allowed on the LRZ cluster. Please submit SLURM batch jobs for performing computations.

General Linux System Documentation

Typical for Linux systems there are (at least) two formats for the system documentation:

  • man pages

  • info pages