Extra Packages for Enterprise Linux (EPEL) is both the Fedora Special Interest Group that creates, maintains, and manages a high quality set of additional packages for Enterprise Linux, and the term referring to the set of packages themselves. EPEL packages are usually based on their Fedora counterparts and rarely conflict with packages in the base Enterprise Linux distributions.
On Peregrine, EPEL is a set of packages installed in a custom location, that are made available to users via
module load epel. The module exposes selected libraries and development packages, from both the base Red Hat Enterprise Linux (RHEL) distribution and the EPEL repository, that are not included in the lightweight OS image on Peregrine's compute nodes, or in some cases on the login nodes. The software components comprising the EPEL installation are special in that they were built to be compatible with the core OS, and so should usually not create version conflicts. Nevertheless, some such conflicts have been noted in the past, and so standing advice for application compatibility with the system is to only load the epel module if it is found to be necessary; otherwise, rely on the core packages in the installed OS images when possible.
To request a package to be added to the EPEL module, email firstname.lastname@example.org with the package name. The package can be from either the core RHEL repository or the EPEL repository. Dependencies will be installed automatically, so there is no need to include them in the request.
Currently installed packages exposed by, e.g., the epel/6.6 module can be found using the command
rpm -qa --dbpath /nopt/nrel/apps/epel/6.6/var/lib/rpm