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CVMFS (CernVM-File System) is a software distribution service heavily used by High-Energy Physics (HEP) experiments to deliver software to multiple different computing systems worldwide. It presents remote software pulled over http as a POSIX read-only file system in user space (normally using FUSE). Access is performant and scalable due to multiple levels of caching such as a local file cache and squid web caches.


Each Perlmutter node has a CVMFS cache on SCRATCH and is connected to CVMFS squid caching proxy servers running on service nodes. If the primary squid caching servers are not avaliable the CVMFS clients on Perlmutter will failover to the off-platform frontier squid caching servers.

NERSC CVMFS Cache system consisting of local node cache with primary CVMFS squid cache and secondary Frontier Squid cache


The CVMFS filesystem is accesible at /cvmfs and can be accessed from any login node or compute node. The current list of supported repositoitories is listed below. If you need a repository added please reach out at

nersc$ ls /cvmfs

CVMFS in Containers

If using shifter you should specify the --modules=cvmfs flag to shifter to make that mount appear inside your container (unless you want to use your own version of cvmfs inside the container).

nersc$ shifter --module=cvmfs

You can also use the new container runtime podman-hpc with CVMFS by mounting the /cvmfs directory into the container.

nersc$ podman-hpc run --rm -it -v /cvmfs:/cvmfs container:tag

CVMFS Batch Jobs

You can also load this module in your batch script and you should also add the cvmfs file system license -L cvmfs which would allow us to pause your jobs from running if the cvmfs mount was unavailable

#SBATCH --module=cvmfs
#SBATCH -L cvmfs