README.md

/etc/systemd/system/ssh_watchdog.service
/usr/local/bin/ssh_watchdog.sh

ssh_watchdog.service

[Unit]
Description=SSH Watchdog

[Service]
ExecStart=/usr/local/bin/ssh_watchdog.sh
Restart=always

[Install]
WantedBy=multi-user.target

ssh_watchdog.sh

#!/bin/bash

# Time in seconds to wait before checking again (e.g., 60 seconds)
CHECK_INTERVAL=60

# Maximum time in seconds without an active SSH connection before shutting down
MAX_IDLE_TIME=600

# Path to the log file
LOG_FILE="/var/log/ssh_watchdog.log"

# Function to check for active SSH connections
check_ssh_connections() {
  # Check if there are active SSH connections
  if ss -t | grep -q ':ssh'; then
    echo "$(date): SSH connection active." >> $LOG_FILE
    return 0
  else
    echo "$(date): No SSH connection found." >> $LOG_FILE
    return 1
  fi
}

# Main loop
idle_time=0

while true; do
  if check_ssh_connections; then
    # Reset idle time if there is an active connection
    idle_time=0
  else
    # Increment idle time if no active connection is found
    idle_time=$((idle_time + CHECK_INTERVAL))
  fi

  # Check if idle time exceeds the maximum allowed idle time
  if [ "$idle_time" -ge "$MAX_IDLE_TIME" ]; then
    echo "$(date): No SSH connections for $MAX_IDLE_TIME seconds. Shutting down." >> $LOG_FILE
    shutdown -h now
    exit 0
  fi

  # Wait for the check interval before checking again
  sleep $CHECK_INTERVAL
done