The CernVM-File System (CernVM-FS) provides a scalable, reliable and low-
maintenance software distribution service. It was developed to assist High
Energy Physics (HEP) collaborations to deploy software on the worldwide-
distributed computing infrastructure used to run data processing applications.
CernVM-FS is implemented as a POSIX read-only file system in user space (a
FUSE module). Files and directories are hosted on standard web servers and
mounted in the universal namespace /cvmfs. Internally, CernVM-FS uses content-
addressable storage and Merkle trees in order to maintain file data and
meta-data. CernVM-FS uses outgoing HTTP connections only, thereby it avoids
most of the firewall issues of other network file systems. It transfers data
and meta-data on demand and verifies data integrity by cryptographic hashes.