CernVM-FS

The distribution of custom software for user groups on the HPC infrastructure is provided using the Cern Virtual Machine File-System (CernVM-FS). CernVM-FS is a read-only network file system based on HTTP and optimized to deliver software in a fast, scalable, and reliable way. Files and file meta-data are cached and downloaded on demand.

Cluster nodes, desktops and interactive machines mount software repositories in the directory /cvmfs/. Every sub-directory is called like the maintainers department, group or experiment name followed by the GSI domain name eg. /cvmfs/fairsoft.gsi.de/ for the Fairoot software or /cvmfs/eel.gsi.de/ for the Experiment Electronics department.

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Usage

Sub-directories in /cvmfs/ will be auto-mounted on demand as soon as they are accessed. This means directories are visible when listing with ls /cvmfs only if they are mounted already.

It is up to the maintainers how to structure the software inside a repository, and how to enable users to load required environment variables to use it.

Repositories

The current list of repositories is available in the Virgo cluster documentation.

Instructions for maintainers

Instuctions for repository maintainers/publishers are available at https://git.gsi.de/dc/cvmfs-server

Best Practice

You should provide a README file in your repository pointing users to information resources, documentation and support.

This file should contain:

• Name and purpose of the software.
• Small how-to for beginners.
• A description of the logical structure of the repository.
• Links to documentation and support pages.
• Your contact information.

You should provide a script to enable users to add your software into their shell environment. The HPC department recommends to use the environment-modules package providing a convenient command called module (→ EnvironmentModules).