Linux Service Watchdog Shell Script (Auto-Restart Failed Services)

Keep critical services running with a service watchdog script that checks systemd units and restarts them if they stop.

What this script does

• Monitors multiple systemd services
• Auto-restarts stopped or failed services
• Logs every action with timestamps
• Optional email alert on restart
• Safe for cron every 5 minutes

Prerequisites

• systemd-based Linux
• Root/sudo for systemctl restart

Step 1: Save the script

sudo nano /usr/local/bin/service-watchdog.sh
sudo chmod +x /usr/local/bin/service-watchdog.sh

Step 2: Full script (scroll to read)

#!/usr/bin/env bash
set -euo pipefail

WATCH_SERVICES=("nginx" "mariadb" "sshd")
ALERT_EMAIL="[email protected]"
LOG="/var/log/service-watchdog.log"

log(){ echo "[$(date '+%F %T')] $*" | tee -a "$LOG"; }

for svc in "${WATCH_SERVICES[@]}"; do
  if ! systemctl is-active --quiet "$svc"; then
    log "Service $svc is down — restarting"
    systemctl restart "$svc" || log "ERROR: failed to restart $svc"
    if [[ -n "$ALERT_EMAIL" ]] && command -v mail >/dev/null; then
      echo "Service $svc was restarted on $(hostname -s)" | mail -s "Watchdog: $svc restarted" "$ALERT_EMAIL"
    fi
  else
    log "Service $svc OK"
  fi
done

Scroll inside the box to read the full script.

Step 3: Configure settings

• WATCH_SERVICES — systemd unit names to monitor
• ALERT_EMAIL — optional notification
• LOG_FILE — action log path

Step 4: Test manually

sudo systemctl stop nginx

sudo /usr/local/bin/service-watchdog.sh

sudo systemctl status nginx

Schedule with cron

sudo crontab -e

Add:

*/5 * * * * /usr/local/bin/service-watchdog.sh >> /var/log/service-watchdog.log 2>&1

Related tutorials

• Linux Disk Monitor Shell Script
• Linux Backup Shell Script: Files & Database to Remote Server
• Cron Jobs in Linux: Schedule Tasks with crontab
• SSH Key Authentication on Linux Servers

Terminal screenshot is an original illustration created for Gnome IT Solutions (blog.gnomeitsolutions.com).