howto.md

HowTo set it up

1. Install the admin_notifications app
2. Create system-notifications.sh with the content from below on your system
3. Add the script to the cronjob crontab -u www-data -e:

0 10 * * * /path/to/file/system-notifications.sh

system-notifications.sh

#!/usr/bin/env bash
#
# @license MIT
# @copyright 2017 Joas Schilling coding@schilljs.com

ADMIN="admin"
OCC_PATH="/var/www/nextcloud/occ"

PACKAGES=$(/usr/lib/update-notifier/apt-check -p 2>&1)
NUM_PACKAGES=$(echo "$PACKAGES" | wc -l)

if [ "$PACKAGES" != "" ]; then
	UPDATE_MESSAGE=$(echo "Packages to update: $PACKAGES" | sed -r ':a;N;$!ba;s/\n/, /g')
	$OCC_PATH notification:generate $ADMIN "$NUM_PACKAGES packages require to be updated" -l "$UPDATE_MESSAGE"

elif [ -f /var/run/reboot-required ]; then
	$OCC_PATH notification:generate $ADMIN "System requires a reboot"
fi

Discuss on https://help.nextcloud.com/t/howto-get-notifications-for-system-updates/10299