diskimage-builder/diskimage_builder/elements/epel/pre-install.d/05-rpm-epel-release

#!/bin/bash

if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
    set -x
fi
set -eu
set -o pipefail

if [[ ${DISTRO_NAME} =~ "centos" ]]; then
    # Centos has "epel-release" in extras, which is default enabled.
    ${YUM} install -y epel-release
else
    # For RHEL, we have to scrape the download page to find the latest
    # release and install that
    [ -n "$ARCH" ]
    if [ 'amd64' = "$ARCH" ] ; then
        ARCH="x86_64"
    fi

    BASE_URL=${DIB_EPEL_MIRROR:-https://dl.fedoraproject.org/pub/epel}
    case "$DISTRO_NAME" in
        rhel7)
            RELEASE=7
            URL=$BASE_URL/$RELEASE/x86_64/Packages/e/
            ;;
        *)
            echo "$DISTRO_NAME is not supported"
            # Not really a failure; we just don't do anything
            exit 0
            ;;
    esac
    PKG_NAME=$(wget -q $URL -O - |grep -oE "(href=\"epel-release-$RELEASE-[0-9,.].*)" | cut -d'"' -f2)
    rpm -q epel-release || yum install -y $URL/$PKG_NAME
fi

if [ ${DIB_EPEL_DISABLED:-0} -ne 0 ]; then
    if [[ ${YUM} == "dnf" ]]; then
        dnf config-manager --set-disabled epel
    else
        yum-config-manager --disable epel
    fi
fi

DIB_EPEL_MIRROR=${DIB_EPEL_MIRROR:-}
[ -n "$DIB_EPEL_MIRROR" ] || exit 0

# Set the EPEL mirror to use
sed -e "s|^#baseurl=http://download.fedoraproject.org/pub/epel|baseurl=$DIB_EPEL_MIRROR|;/^mirrorlist=/d;/^metalink=/d" -i /etc/yum.repos.d/epel.repo