bash script + systemd units for auto-shutting down an idle machine (no active ssh logins)

auto_shutdown.service

[Unit]
Description=Auto shutdown service

[Service]
Type=oneshot
ExecStart=/auto_shutdown.sh

auto_shutdown.sh

#!/bin/bash
set -euo pipefail
set -x

# Set the threshold in seconds, 10 minutes = 600 seconds
#threshold=900
threshold=3600

# Check for active SSH connections
if ! active_connections=$(who | grep -E 'pts|tty' | grep -v tmux | wc -l); then
  active_connections=0
fi

if [[ $active_connections -eq 0 ]]; then
  if [[ ! -f /run/last_empty ]]; then
    # Create a file with the current timestamp if no active connections and the file doesn't exist
    date +%s > /run/last_empty
  else
    last_empty=$(cat /run/last_empty)
    now=$(date +%s)

    if [[ $((now - last_empty)) -ge $threshold ]]; then
      # Shutdown the VM if the threshold is reached
      rm /run/last_empty
      shutdown -h now
    fi
  fi
else
  # Remove the file if there are active connections
  rm -f /run/last_empty
fi

auto_shutdown.timer

[Unit]
Description=Auto shutdown timer

[Timer]
OnBootSec=5min
OnUnitActiveSec=1min
Unit=auto_shutdown.service

[Install]
WantedBy=timers.target