π ~1 min read
Table of contents
Symptom & Impact
Hostnames cannot be resolved, breaking package updates and service discovery.
Environment & Reproduction
Common after manual edits to resolv.conf or resolver service changes.
Root Cause Analysis
Resolver symlink drift, invalid upstream nameservers, or service inactivity causes lookup failures.
Quick Triage
Confirm resolver daemon health and current DNS servers.
Step-by-Step Diagnosis
Trace query path and validate /etc/resolv.conf link target.
Solution – Primary Fix
Restore proper resolv.conf linkage, define valid DNS servers, and restart resolver.
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Solution – Alternative Approaches
Use static resolv.conf with managed updates disabled for specialized environments.
Verification & Acceptance Criteria
Name resolution succeeds consistently across required domains.
Rollback Plan
Restore prior resolved.conf and resolv.conf backups if resolver behavior regresses.
Prevention & Hardening
Standardize DNS configuration management and monitor resolver health.
Related Errors & Cross-Refs
Related to Temporary failure in name resolution and failed DNS lookup messages.
Related tutorial: View the step-by-step tutorial for Debian 11.
View all Debian 11 tutorials on the Tutorials Hub β
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
systemd-resolved administration and Debian networking references.
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