IBM AIX 7.2 – Common Problem 166 – Diagnosis and Fix

📖 ~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

Application servers cannot resolve external hostnames. Backups, monitoring agents, and patch downloads all fail until DNS is restored.

Environment & Reproduction

Occurs after manual edits to /etc/resolv.conf or /etc/netsvc.conf.

cat /etc/resolv.conf
oslevel -s
uname -a

Root Cause Analysis

Cause is misconfigured resolver order, unreachable nameservers, or netcd cache holding stale entries.

Quick Triage

Verify resolver config, reachability, and name-service switch.

cat /etc/resolv.conf

Step-by-Step Diagnosis

Capture deeper evidence to isolate the failure path.

cat /etc/resolv.conf
cat /etc/netsvc.conf
host google.com
nslookup google.com
lssrc -s netcd

Solution – Primary Fix

Apply the proven primary fix in a controlled change window.

cat > /etc/resolv.conf <<EOF
search example.com
nameserver 10.0.0.2
nameserver 10.0.0.3
EOF
stopsrc -s netcd
startsrc -s netcd
netcdctl -c hosts

Solution – Alternative Approaches

Use these alternatives when the primary fix is blocked by environmental constraints.

echo 'hosts = local, bind' > /etc/netsvc.conf
refresh -s netcd

Verification & Acceptance Criteria

Confirm the system meets acceptance criteria after the change.

host pkg.ibm.com
nslookup -timeout=2 pkg.ibm.com 10.0.0.2
dig @10.0.0.2 pkg.ibm.com

Rollback Plan

Revert cleanly if regressions appear during validation.

cp /etc/resolv.conf.bak /etc/resolv.conf
stopsrc -s netcd
startsrc -s netcd

Prevention & Hardening

Reduce recurrence with monitoring and preventive tuning.

errnotify -a 'en_name=netcd'
chsubsys -s netcd -a '-T 600'
backup /etc/resolv.conf weekly

Related Errors & Cross-Refs

Related to firewall changes, IPv6 misrouting, and NIS/LDAP fallback issues.

Related tutorial: View the step-by-step tutorial for aix-7.2.

View all aix-7.2 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

IBM AIX 7.2 Networks and Communications, resolv.conf and netsvc.conf man pages.