📖 ~1 min read
Table of contents
Symptom & Impact
Hostnames fail intermittently, causing package, API, and service connectivity errors.
Environment & Reproduction
Appears after network changes, DHCP renewals, or resolver configuration drift.
Root Cause Analysis
Incorrect nameserver order, stale resolv.conf updates, or unreachable upstream DNS.
Quick Triage
Run direct dig tests and compare resolver file with active network settings.
Step-by-Step Diagnosis
Trace name resolution path from local cache through upstream servers.
Solution – Primary Fix
Normalize DNS configuration and restart networking or resolver components.
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Solution – Alternative Approaches
Use reliable fallback resolvers and pin explicit DNS in interface configuration.
Verification & Acceptance Criteria
Repeated forward and reverse lookups succeed without timeout or SERVFAIL.
Rollback Plan
Restore previous resolver and interface files from backup snapshots.
Prevention & Hardening
Monitor DNS latency and keep resolver settings managed through one source.
Related Errors & Cross-Refs
Frequently tied to proxy issues, mirror failures, and TLS verification problems.
Related tutorial: View the step-by-step tutorial for Debian 10.
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References & Further Reading
Debian networking and resolver behavior documentation.
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