ntfy
ntfy lets you send push notifications to your phone or desktop via scripts from any computer, using simple HTTP PUT or POST requests.

🔔 Low Space
Script 
 #!/bin/bash

mingigs=20
avail=$(df | awk '$6 == "/" && $4 < '$mingigs' * 1024*1024 { print $4/1024/1024 }')

if [ -n "$avail" ]; then
 curl \
 -H "Title: Low Disk Space" \
 -H "Priority: urgent" \
 -H "Tags: warning,cd" \
 -d "Hello TTBB! Only $avail GB available on the root disk. Better clean that up." \
 https://notify.boreux.work/raspberrypi?auth=<TOKEN>
fi
 
 Cron 
 0 * * * * root /bin/bash /root/ntfy/low-disk-space.sh

⛔️ SSH Access
Script 
 #!/bin/bash
if [ "${PAM_TYPE}" = "open_session" ]; then
 curl \
 -H "Title: SSH Login" \
 -H "Priority: urgent" \
 -H "Tags: warning,door" \
 -d "Hello TTBB! There was an SSH login with user ${PAM_USER} from ${PAM_RHOST} host" \
 https://notify.boreux.work/pihole?auth=<TOKEN>
fi
 
 /etc/pam.d/sshd 
 At the end of the file, add the following line: 
 session optional pam_exec.so /root/ntfy/ssh-login.sh

🐚 Useful Commands
Creating an Administrator 
 docker exec -it <NTFY_CONTAINER_NAME> ntfy user add --role=admin <USERNAME>