Ubuntu 20.04 LTS – sudo reports unable to resolve host

📖 ~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

Every sudo command prints hostname resolution warning and delays execution.

Environment & Reproduction

Often appears after hostname changes not mirrored in local hosts mapping.

Root Cause Analysis

Current hostname does not resolve locally via /etc/hosts entry.

Quick Triage

Compare hostnamectl output against /etc/hosts and resolver configuration.

Step-by-Step Diagnosis

Validate short and FQDN mappings for active hostname.

Solution – Primary Fix

Align /etc/hostname and /etc/hosts records, then restart relevant services.

Solution – Alternative Approaches

Set a temporary hostname matching existing hosts mapping until maintenance window.

Verification & Acceptance Criteria

sudo runs without hostname resolution warnings or delays.

Rollback Plan

Restore prior hostname configuration if dependent service discovery breaks.

Prevention & Hardening

Use standardized hostname change procedures with automated hosts updates.

Related Errors & Cross-Refs

sudo: unable to resolve host and getaddrinfo temporary failure.

Related tutorial: View the step-by-step tutorial for Ubuntu 20.04 LTS.

View all Ubuntu 20.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Ubuntu hostname management and local resolver configuration guidance.