A script that sends a telegram message when an ubuntu server needs update or reboot

update-reboot-check.sh

#!/bin/bash
IFS=';' read updates security_updates < <(/usr/lib/update-notifier/apt-check 2>&1)
HOSTNAME=`hostname`
BOT_TOKEN='THISTOKENISFROMBOTFATHER'
# Numeric id of the chat to publish messages to
CHAT_ID=1234567890

if [ ! -f ".update-check-status" ] ; then
    echo "0:0" > .update-check-status
fi

CONTROL="$updates:$security_updates"
HASCHANGED=false
ACTUALSTATE=`cat .update-check-status`

if [ "$ACTUALSTATE" != "$CONTROL" ]; then
    HASCHANGED=true
    echo $CONTROL > .update-check-status
fi

function send_message {
    curl -s -X POST https://api.telegram.org/bot$BOT_TOKEN/sendMessage -d chat_id=$CHAT_ID -d text="$1" -d parse_mode="markdown" > /dev/null
}

if [ $updates -gt 0 ] || [ $security_updates -gt 0 ] ; then
    if $HASCHANGED; then
        send_message "There are *$updates* updates available for *$HOSTNAME* and *$security_updates* of them are security updates"
    fi
fi

if [ -f /var/run/reboot-required ]; then
    send_message "Reboot needed on *$HOSTNAME*"
fi

The script uses /usr/lib/update-notifier/apt-check to check if new updates are available and saves the state in a hidden file (.update-check-status) in order to prevent repeating messages.

The script is than launched hourly with crontab.

To create the telegram bot, you can follow this article.

Needs curl to work properly.