Troubleshooting:Service Troubleshooting

This guide covers troubleshooting for reverse proxy services.

Common Issues

Issue: 502 Bad Gateway

Causes:

• Backend not running (Docker on VPS or service on NAS)

• Caddy misconfigured or not reloaded after Caddyfile change

• Wrong port number

• Service not accessible via VPN

Solutions:

==== Test from VPS to NAS ====
ping 10.8.0.2
curl http://10.8.0.2:PORT_NUMBER

== Check if service is listening ==
== (from Synology NAS or via SSH) ==
netstat -tlnp | grep PORT_NUMBER

Issue: SSL Certificate Failed

Causes:

• DNS not pointing to VPS

• Port 80 blocked

• Rate limiting from Let's Encrypt

Solutions:

==== Check DNS ====
nslookup newservice.jb-vpn.uk

== Verify port 80 is open ==
curl -I http://newservice.jb-vpn.uk

== Check firewall ==
sudo iptables -L -n -v | grep 80

Issue: Service Not Loading

Causes:

• Wrong proxy_pass URL

• Missing headers

• Service requires specific path

Solutions:

• Check Caddy: journalctl -u caddy -n 50

• Verify backend directly: curl http://127.0.0.1:PORT (VPS) or curl http://10.8.0.2:PORT (NAS via VPN)

• Test with different proxy_pass formats

Issue: Connection Timeout

Causes:

• VPN tunnel down

• Service not accessible

• Firewall blocking

Solutions:

==== Check VPN ====
ip addr show tun0
ping 10.8.0.2

== Check routing ==
ip route | grep 10.8.0.2

== Test connectivity ==
curl -v http://10.8.0.2:PORT_NUMBER

Diagnostic Commands

=== Check service status ===
systemctl status nginx

== Test nginx configuration ==
nginx -t

== View error logs ==
tail -f /var/log/nginx/error.log

== View access logs ==
tail -f /var/log/nginx/access.log

== Check SSL certificates ==
certbot certificates

== Test service directly ==
curl -I https://service.jb-vpn.uk

Related Documentation

• [Adding Services](index.md) - Service configuration

• [System Overview](index.md) - System architecture