Software Distribution

Software distribution in the EGI infrastructure

This page documents usage the CernVM-FS (CVMFS) service operated for EGI by UKRI-STFC.


The CernVM-File System (CVMFS) provides a scalable, reliable and low-maintenance software distribution service. It was developed to assist High Energy Physics collaborations to deploy software on the worldwide distributed computing infrastructure used to run data processing applications. CVMFS is implemented as a POSIX read-only file system in user space. Files and directories are hosted on standard web servers and mounted in the universal namespace /cvmfs. CernVM-FS uses outgoing HTTP connections only, thereby it avoids most of the firewall issues of other network file systems. It transfers data and metadata on demand and verifies data integrity by cryptographic hashes. CVMFS is actively used by small and large collaborations. In many cases, it replaces package managers and shared software areas on cluster file systems as means to distribute the software used to process experiment data.

This documentation is for the VO content managers.

Official CVMFS pages

Requesting the creation of a new repository

In the case of a new repository for EGI, steps are described in PROC22.

Onboarding new Content Managers

Steps for a new VO Content Manager to be granted access to the Stratum-0.

Requesting access

Request access to the service sending an email to In the email, include the following information:

Mailing list

All VO content managers should join the CVMFS-UPLOADER-USERS mailing list in JISCMAIL.

Distributing new content

To log into the service, just use ssh. You need to specify explicitly which username you want to use to log in. The username is composed as reponame+"sgm". For example, for the repository, the username is diracsgm.

# Replace with the proper username
$ ssh

To copy data:

# Replace with the proper username
$ scp source_file.txt

When running the ssh or scp commands, a message like this is displayed:

# Replace with the proper username
$ ssh
Authenticate at
Hit enter when you have finished authenticating

Copy and paste the URL into a browser, and follow the instructions to authenticate yourself using your home institution Identity Management Service.

After login, you will find a single directory in the home directory:

$ ls

Add to that directory the new content you want to distribute.

Files and directories cannot be distributed with CVMFS if they are not world-wide readable. You may want to ensure they have the right permissions with the following commands:

$ find . -type d -exec chmod go+rx {} \;
$ find . -type f -exec chmod go+r {} \;

Building your software

CVMFS is an infrastructure to distribute software world-wide. However, the uploader host should not be used for the purposes of building and compiling it prior to distribution.

The right approach is for you to have your own local building environment, and use the uploader host only to upload the new content for distribution.

If you have non-relocatable software, then you will need a /cvmfs/<myrepo>/ directory on your building host. One option is to use an actual CVMFS client, so you have ready all the existing content being already distributed by CVMFS. By default, the /cvmfs/ directory on a CVMFS client host is read-only, but that can be solved using an ephemeral writable container.