📖 ~1 min read
Table of contents
Symptom & Impact
DNS lookups intermittently fail and dependent services time out.
Environment & Reproduction
Debian 10 servers rely on mixed resolv.conf management and changing network links.
Root Cause Analysis
Resolver configuration drift and unreachable upstream nameservers break resolution.
Quick Triage
Test direct queries against each configured nameserver and note failures.
Step-by-Step Diagnosis
Inspect resolv.conf ownership, network manager hooks, and resolver timeout behavior.
Solution – Primary Fix
Set authoritative resolver configuration and remove conflicting writers.
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Solution – Alternative Approaches
Deploy local caching resolver to stabilize latency and upstream failures.
Verification & Acceptance Criteria
Consistent DNS answers return quickly for internal and public domains.
Rollback Plan
Restore prior resolver files and service configuration from backups.
Prevention & Hardening
Monitor DNS latency and enforce single source of truth for resolver settings.
Related Errors & Cross-Refs
Related to routing asymmetry and firewall egress drops on DNS ports.
Related tutorial: View the step-by-step tutorial for debian-10.
View all debian-10 tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Debian resolver stack and DNS diagnostics best practice documentation.
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