My personal CentOS configuration scripts: installs elrepo, epel, enables centosplus and PowerTools, sets sudoers to require root password, enables some nano settings, fixes dnf tab completion if system is centos 8. Written on CentOS 8, only somewhat tested on CentOS 7

centos-config.sh

#!/usr/bin/env bash

if  (( EUID != 0 ))
then
        echo "Script should be run as root"
        exit 1
else
        echo "Detected running as root"
fi

if [[ $(cat /etc/centos-release | cut -d ' ' -f 4 | cut -d '.' -f 1) -ge 8 ]]
then
  CENTVER="8+"
  ELREPO="https://www.elrepo.org/elrepo-release-8.0-2.el8.elrepo.noarch.rpm"
  PACKAGE_MANAGER="dnf"
else
  CENTVER="7"
  ELREPO="https://www.elrepo.org/elrepo-release-7.0-4.el7.elrepo.noarch.rpm"
  PACKAGE_MANAGER="yum"
fi
echo ${PACKAGE_MANAGER}
# Configure shell
wget -O /etc/profile.d/colorprompt.sh https://gist.githubusercontent.com/kholis/3985921/raw/d55393f64c4a21dbd419c769548c6319a21d84b4/colorprompt.sh

if [ "${CENTVER}" == "8+" ]
then
  # Enable centosplus
  sed -i 's/enabled=0/enabled=1/' /etc/yum.repos.d/CentOS-centosplus.repo

  # Enable PowerTools
  sed -i 's/enabled=0/enabled=1/' /etc/yum.repos.d/CentOS-PowerTools.repo
  if [[ -f /etc/yum.repos.d/CentOS-Stream-PowerTools.repo ]]
  then
        sed -i 's/enabled=0/enabled=1/' /etc/yum.repos.d/CentOS-Stream-PowerTools.repo
  fi
fi

# Install epel
"${PACKAGE_MANAGER}" install -y epel-release

# Install elrepo
rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org

"${PACKAGE_MANAGER}" install -y "${ELREPO}"
sed -i 's/enabled=0/enabled=1/4' /etc/yum.repos.d/elrepo.repo

# Require root password for sudo
echo "Defaults rootpw" > /etc/sudoers.d/Require_Root_Pass

# Modify nano, CentOS 7 has an older version so some options arent'y the same
if [ "${CENTVER}" == "8+" ]
then
  sed -i 's/# set smooth/set smooth/' /etc/nanorc
  sed -i 's/# set constantshow/set constantshow/' /etc/nanorc
else
  sed -i 's/# set smooth/set smooth/' /etc/nanorc
  sed -i 's/# set const/set const/' /etc/nanorc
fi

echo ${CENTVER}

# Fix DNF tab completion
if [ "${CENTVER}" == "8+" ]
then
  echo "fixing dnf tab completion"
  "${PACKAGE_MANAGER}" install python36
  wget -O /usr/lib/python3.6/site-packages/dnf/cli/completion_helper.py https://raw.githubusercontent.com/rpm-software-management/dnf/master/dnf/cli/completion_helper.py.in
  sed -i -e 's/@PYTHON_EXECUTABLE@/\/usr\/libexec\/platform-python/g' /usr/lib/python3.6/site-packages/dnf/cli/completion_helper.py
fi