HPC @ Uni.lu

High Performance Computing in Luxembourg

Working directories

After a successful login onto one of the access node (see Cluster Access), you end into your personal home directory $HOME which is shared over GPFS between the access node and the computing nodes.

Thus every piece of data transferred within $HOME is reachable (under the same path) on the computing nodes.

The Directory Structure is actually more complex and define in your environment the following paths with specific properties:

  • $HOME: your home directory under GPFS This directory is under a regular backup policy, except for Iris.
  • $SCRATCH is also a non-backed up area put if possible under Lustre for fast I/O operations. The $SCRATCH filesystem is for applications which are I/O intensive and benefit from high read/write speed, and only temporarily need a large amount of disk space. Use the alias cds to quickly change your current directory to $SCRATCH.

    • under iris, all files not accessed for more than 60 days will be removed.
  • PROJECT directories are partially backed up, only the files placed under the /backup subdirectory will be backed up.
Avoid hard-coding paths inside your code, use the environment variables `$HOME`, `$SCRATCH`, `$PROJECTWORK` as much as possible.

Important The below tables list the quota restrictions applied to these directories - they are likely to evolve over time. The commands given in the last column allows you to read from the access nodes: the storage capacity and the number of files used in your directories.

Directory Max size Max #files Backed up Storage usage command
$HOME 500 GB 1.000.000 YES df-ulhpc
$SCRATCH 10 TB 1.000.000 NO df-ulhpc
$PROJECT per request   PARTIALLY (/backup subdir) df-ulhpc

In order to apply for both project folders or project folder extensions please open a ticket.


bash is the default shell. To change your login shell to other shells, please send a request to the system administrators.

Note We currently support the following login shells:

Operating Systems

Each computing node runs the Centos Linux operating system, version 7 (or Debian Linux in the case of Chaos, Gaia and G5K) and you’ll have to interface with them by using the command line.

Thus, you are more than encouraged to become familiar - if not yet - with Linux commands. We can recommend the following sites and resources:

Software - Environment modules

The UL HPC provides environment modules with the module command to manage the user environment, e.g. changing the environment variables.

By loading appropriate environment modules, the user can select:

  • compilers,
  • libraries, e.g. the MPI library, or
  • other third party software packages.

An exhaustive list of the available software is proposed in this page.

Compiling your code