Disk usage monitor for a single disk that posts to Slack if the usage percent surpasses a configurable threshold.

disk-monitor.sh

#!/bin/bash
PERCENT_THRESHOLD=95
DISK_NAME=/dev/sda1
DISK_PERCENTAGE=$(df -hl $DISK_NAME | sed 1d | awk 'BEGIN{print "Use%"} {percent+=$5;} END{print percent}' | column -t | sed 1d);
if (( $PERCENT_THRESHOLD <= $DISK_PERCENTAGE )); then
        curl -X POST -H 'Content-type: application/json' --data "{\"text\":\"Disk is almost full - $DISK_PERCENTAGE% used on $DISK_NAME. Threshold set to $PERCENT_THRESHOLD%.\"}" https://hooks.slack.com/services/XXXXXXXXX/XXXXXXXXX/XXXXXXXXXXXXXXXXXXXXXXXXX
fi

1. Set the disk usage percent threshold (line 2)
2. Set disk path (run command "df" to find the correct disk path) (line 3)
3. Insert your own Slack cURL call / update the Slack URL (line 6)
4. Add the path of this script to your crontab at desired interval. This example will run every 3rd hour: "0 */3 * * * /path/to/your/disk-monitor.sh". Use crontab.guru to generate an interval that suits you.
5. Et voilà!