This page describes how to automatically update your arch sytem.

First create the necessary configuration and systemd files

/etc/archupgrade.conf

# ignore packages to be updated
# multiple packages seperated by comma
ignore="linux,pacman"
log="/var/log/archupgrade.log"
mailto="<your mail address>"

/etc/sytemd/system/archupgrade.timer

[Unit]
Description=Upgrade arch

[Timer]
OnCalendar=Wed 02:07:00
Persistent=true
Unit=archupgrade.service

[Install]
WantedBy=default.target

/etc/systemd/system/archupgrade.service

[Unit]
Description=Upgrade arch with pacman

[Service]
Type=oneshot
User=root
Environment=SHELL=/bin/sh
Environment=PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
ExecStart=/usr/local/bin/archupgrade minimal reboot

Once your have created the files above add the script to run the update in /usr/local/bin/archupgrade and make it executable (moreutils package is a dependency for ts)

#!/bin/bash

function log() {
	date=$(date +'%Y-%m-%d %H:%M')
 echo "[$date] $1" >> $log 2>&1
}

function mail() {
	host=$(hostname)
	day=$(date +'%Y-%m-%d')
	msg=$(grep "$day" $log)
	echo -e "$msg" | mailx -s "Arch upgrade: $host" $mailto
}


function list_updates() {
	list=$(pacman -Qu)
	if [ $? -ne 0 ]; then
		echo "nothing to do"
		exit 0
	else
		echo "$list"
	fi
}

function will_reboot() {
 dd=$(date +'%Y-%m-%d')
 grep $dd $log | grep "upgrading linux..."
 if [ $? -eq 0 ]; then
 log "Will reboot in 10 minutes"
		shutdown -r +10
	else
		log "no linux kernel upgrade"
	fi
}

function minimal() {
	pacman -Syu --ignore=$ignore --noconfirm --overwrite '*' | tee -a $log
	if [ $? -ne 0 ]; then
		log "Upgrade not complete"
		mail "Minimal upgrade not complete"
		exit 1
	fi

	log "minimal upgrade done"

 if [ $reboot -eq 1 ]; then
		will_reboot
	fi
	mail "minimal upgrade done"
}

function full() {
 # do an archlinux-keyring before upgrading
	sudo pacman -Sy --noconfirm archlinux-keyring | ts '[%Y-%m-%d %H:%M:%S]' | tee -a $log
	sudo pacman -Syu --noconfirm --overwrite '*' | ts '[%Y-%m-%d %H:%M:%S]' | tee -a $log
	if [ $? -ne 0 ]; then
		log "Upgrade not complete"
		mail "Full upgrade not complete"
		exit 1
	fi

 if [ $reboot -eq 1 ]; then
		will_reboot
	fi
	mail "full upgrade done"
}

config="/etc/archupgrade.conf"
if [ ! -f $config ]; then
	echo "No config file found: $config"
	exit 1
fi
 source $config
pacman -Sy

reboot=$2
if [ -z $reboot ]; then
	reboot=0
else
 reboot=1
fi

case "$1" in
	list_updates)
		list_updates
		;;
	minimal)
		minimal $2
		;;
	full)
		full $2
		;;
	*)
		echo "$0 <list_updates|minimal|full> [reboot]"
		echo "reboot: will only reboot if a kernel update has been done"
		exit 0
		;;
esac

chmod 700 /usr/local/bin/archupgrade

Now enable the timer

systemctl enable --now archupgrade.timer