RPi change hostname at boot

dynhost.sh

##
# DYNHOST SCRIPT
##

> nano /root/dynhost.sh

#!/bin/bash
name=rpi
source /boot/config.txt
hostnamectl set-hostname "$name"

# ADD name=the-name in /boot/config.txt

##
# SYSTEMD UNIT
##

> nano /etc/systemd/system/dynhost.service

[Unit]
Description=Dynamic Hostname
After=systemd-hostnamed.service

[Service]
Type=oneshot
ExecStart=/root/dynhost.sh

[Install]
WantedBy=multi-user.target

> systemctl enable dynhost