Ubuntu 18.04 LTS SSL Certificate Chain Incomplete in Nginx

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Clients receive certificate warnings or TLS handshake failures against hosted services.

Environment & Reproduction

Nginx on Ubuntu 18.04 using incorrectly bundled server certificate files.

Root Cause Analysis

Intermediate CA certificates are omitted, so clients cannot build a trust chain.

Quick Triage

Test endpoint with openssl s_client and verify what chain elements are returned.

Step-by-Step Diagnosis

Review Nginx ssl_certificate paths, inspect PEM content order, and validate key-certificate pairing.

Solution – Primary Fix

Deploy proper fullchain file, reload Nginx, and confirm complete chain presentation to clients.

Solution – Alternative Approaches

Use ACME automation tooling to maintain correct chain bundles automatically.

Verification & Acceptance Criteria

External SSL checks pass without trust warnings across major client platforms.

Rollback Plan

Restore prior certificate files if new deployment causes key mismatch or service outage.

Prevention & Hardening

Automate certificate deployment validation with pre-reload checks.

Related Errors & Cross-Refs

Related to expired certificates, hostname mismatch, and OCSP stapling misconfiguration.

Related tutorial: View the step-by-step tutorial for Ubuntu 18.04 LTS.

View all Ubuntu 18.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

See Nginx TLS configuration docs and CA chain validation practices.