🟠 High   ⏱ 5–30 min  Last verified: 19 May 2026
Affected versions: Ubuntu 24.04 LTS

πŸ“– ~1 min read

Table of contents
  1. Symptom & Impact
  2. Environment & Reproduction
  3. Root Cause Analysis
  4. Quick Triage
  5. Step-by-Step Diagnosis
  6. Solution – Primary Fix
  7. Solution – Alternative Approaches
  8. Verification & Acceptance Criteria
  9. Rollback Plan
  10. Prevention & Hardening
  11. Related Errors & Cross-Refs
  12. References & Further Reading

Symptom & Impact

Hostnames fail to resolve, breaking updates and outbound service access.

Environment & Reproduction

Often appears after DNS server change or network profile updates.

resolvectl status
ping -c 2 google.com
sudo apt update

Root Cause Analysis

Incorrect upstream DNS settings or resolver instability causes name lookup failure.

Quick Triage

Verify local stub resolver health and test direct lookup.

systemctl status systemd-resolved
resolvectl query ubuntu.com
getent hosts archive.ubuntu.com

Step-by-Step Diagnosis

Trace resolver path from local stub to upstream nameservers.

cat /etc/resolv.conf
resolvectl dns
resolvectl statistics
sudo journalctl -u systemd-resolved -n 100
Illustrative mockup for ubuntu-24-04-lts β€” terminal_or_shell
DNS and resolver diagnostics β€” Illustrative mockup β€” Progressive Robot

Solution – Primary Fix

Set valid nameservers in netplan and restart resolver.

Still having issues? Our IT Solutions & Services team can diagnose and resolve this for you. Get in touch for a free consultation.

sudoedit /etc/netplan/01-netcfg.yaml
sudo netplan generate
sudo netplan apply
sudo systemctl restart systemd-resolved
Illustrative mockup for ubuntu-24-04-lts β€” logs_or_journal
resolved service logs for lookup failures β€” Illustrative mockup β€” Progressive Robot

Solution – Alternative Approaches

Apply temporary interface-level DNS for short-term recovery.

sudo resolvectl dns eth0 1.1.1.1 8.8.8.8
sudo resolvectl flush-caches

Verification & Acceptance Criteria

Internal and external domains resolve consistently.

resolvectl query security.ubuntu.com
ping -c 2 security.ubuntu.com
sudo apt update

Rollback Plan

Restore previous netplan file if new DNS values introduce routing issues.

sudo cp /etc/netplan/01-netcfg.yaml.bak /etc/netplan/01-netcfg.yaml
sudo netplan apply

Prevention & Hardening

Standardize resolver settings and monitor systemd-resolved health.

systemctl is-enabled systemd-resolved
resolvectl statistics

Frequently overlaps with VPN split DNS and proxy misconfiguration.

Related tutorial: View the step-by-step tutorial for Ubuntu 24.04 LTS.

View all Ubuntu 24.04 LTS tutorials on the Tutorials Hub β†’

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Ubuntu networking and resolver documentation.

Need Expert Help?

If you cannot resolve this yourself, our team offers hands-on Server Management, Managed IT Services, and flexible Support Plans. Contact us today β€” we respond within one business day.