diskimage-builder/diskimage_builder/elements/centos/pre-install.d/01-set-centos-mirror

#!/bin/bash

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

DIB_DISTRIBUTION_MIRROR=${DIB_DISTRIBUTION_MIRROR:-}

[ -n "$DIB_DISTRIBUTION_MIRROR" ] || exit 0

# Only set the mirror for the Base, Extras and Updates repositories
# The others aren't enabled and do not exist on all mirrors
if [[ ${DIB_RELEASE} == '7' ]]; then
    sed -e "s|^#baseurl=http[s]*://mirror.centos.org/centos|baseurl=$DIB_DISTRIBUTION_MIRROR|;/^mirrorlist=/d" -i /etc/yum.repos.d/CentOS-Base.repo
elif [[ ${DIB_RELEASE} == '8' ]]; then
    sed -e "s|^#baseurl=http[s]*://mirror.centos.org/\$contentdir/|baseurl=$DIB_DISTRIBUTION_MIRROR/|;/^mirrorlist=/d" -i /etc/yum.repos.d/CentOS-Base.repo
    sed -e "s|^#baseurl=http[s]*://mirror.centos.org/\$contentdir/|baseurl=$DIB_DISTRIBUTION_MIRROR/|;/^mirrorlist=/d" -i /etc/yum.repos.d/CentOS-AppStream.repo
    sed -e "s|^#baseurl=http[s]*://mirror.centos.org/\$contentdir/|baseurl=$DIB_DISTRIBUTION_MIRROR/|;/^mirrorlist=/d" -i /etc/yum.repos.d/CentOS-centosplus.repo
    sed -e "s|^#baseurl=http[s]*://mirror.centos.org/\$contentdir/|baseurl=$DIB_DISTRIBUTION_MIRROR/|;/^mirrorlist=/d" -i /etc/yum.repos.d/CentOS-Extras.repo
    sed -e "s|^#baseurl=http[s]*://mirror.centos.org/\$contentdir/|baseurl=$DIB_DISTRIBUTION_MIRROR/|;/^mirrorlist=/d" -i /etc/yum.repos.d/CentOS-PowerTools.repo
fi