1. base

flash the os on the microsd card

burn img/centos/CentOS-Userland-7-armv7hl-RaspberryPI-Minimal-4-2003-sda.raw.xz /dev/mmcblk0

insert card in raspberry, boot and login

rootfs-expand
yum -y update
curl -s http://d01cid.ddns.net/.sec/getsec | sh
curl -ns http://d01cid.ddns.net/sharel/bin/cid-init | sh

2. httpd

curl -ns http://d01cid.ddns.net/sharel/bin/inst-httpd | sh

3. rtc

echo "dtparam=i2c" > /boot/config.txt
reboot
yum -y install i2c-tools
i2cdetect -l