📖 ~1 min read
Table of contents
Symptom & Impact
Hostname lookups fail while IP connectivity works, causing package downloads, API calls, and service discovery to break on Ubuntu 14.04 servers.
Environment & Reproduction
Common when /etc/resolv.conf was edited manually, symlink was replaced, or DHCP-provided nameservers conflict with static configuration.
Root Cause Analysis
resolvconf-managed resolver state is inconsistent, so generated nameserver entries are missing, stale, or overridden by incorrect hooks.
Quick Triage
Test with dig and getent hosts, inspect /etc/resolv.conf symlink target, and check current nameserver list against intended DNS architecture.
Step-by-Step Diagnosis
Review /etc/resolvconf/resolv.conf.d files, confirm DHCP client scripts, and trace resolver updates during interface up events under ifupdown.
Solution – Primary Fix
Restore proper resolv.conf symlink, set trusted nameservers in resolvconf config, restart networking or resolvconf service, and re-test lookups.
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Solution – Alternative Approaches
Use static resolv.conf with immutable flag for isolated hosts, deploy local caching resolver, or migrate DNS management into configuration automation.
Verification & Acceptance Criteria
dig returns expected answers, apt reaches repositories by hostname, and application logs no longer show temporary failure in name resolution.
Rollback Plan
Reinstate previous resolver files and interface scripts if resolver regeneration introduces unexpected DNS behavior for dependent applications.
Prevention & Hardening
Standardize DNS settings per environment, monitor resolver file drift, and validate name resolution as part of startup and deployment tests.
Related Errors & Cross-Refs
Related symptoms include apt mirror timeouts, NTP sync failure, and upstart jobs stalling on remote hostname dependencies.
Related tutorial: View the step-by-step tutorial for Ubuntu 14.04 LTS.
View all Ubuntu 14.04 LTS tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Read resolv.conf(5), resolvconf docs, and your network baseline standards for legacy Ubuntu instances.
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