Checks and ensures that the ntpd service is started and running, and sets it to start at system boot.

ntp.sh

#!/bin/bash

# Check if ntp is installed, and, if not, install it.
if ! rpm -qa | grep -qw ntp; then
    yum install -y ntp
fi

# Start ntpd if it's not already running.
if ps aux | grep -v grep | grep "[n]tpd" > /dev/null
then
    echo "ntpd is running." > /dev/null
else
    systemctl start ntpd.service > /dev/null
    echo "Started ntpd."
fi
# Make sure ntpd is enabled on system startup.
systemctl enable ntpd.service