π ~1 min read
Table of contents
Symptom & Impact
Host DNS lookups randomly fail despite network connectivity.
Environment & Reproduction
Temporary failure in name resolution appears for apt, curl, and system services.
Root Cause Analysis
Inspect resolvectl status, check upstream DNS reachability, and review journalctl -u systemd-resolved -b.
Quick Triage
Invalid DNS servers from DHCP, split DNS mismatch, or stale cache behavior under network changes.
Step-by-Step Diagnosis
Set reliable nameservers in netplan or resolved config and restart systemd-resolved to refresh state.
Solution – Primary Fix
Run resolvectl query and apt update to confirm stable resolution over time.
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Solution – Alternative Approaches
Standardize DNS via DHCP reservations or static netplan definitions for critical servers.
Verification & Acceptance Criteria
Revert to prior nameserver set and flush caches if new policy degrades lookup performance.
Rollback Plan
Continuously test DNS health endpoints and alert on lookup latency spikes.
Prevention & Hardening
resolvectl status; resolvectl flush-caches; journalctl -u systemd-resolved -b
Related Errors & Cross-Refs
Provide resolver logs, DHCP lease details, and failing domain examples.
Related tutorial: View the step-by-step tutorial for Ubuntu 26.04 LTS.
View all Ubuntu 26.04 LTS tutorials on the Tutorials Hub β
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Containerized workloads may inherit host resolver issues and amplify intermittent failures.
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