IBM AIX 7.3 – Common Problem 213 – 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

ssh logins fail or hang after PAM or sshd configuration changes.

Environment & Reproduction

OpenSSH installed via bos.net or expansion pack with custom /etc/ssh/sshd_config.

lssrc -s sshd
tail /var/adm/messages
cat /etc/ssh/sshd_config

Root Cause Analysis

PAM stack, /etc/security/login.cfg, or sshd_config block authentication paths.

Quick Triage

Check sshd status and recent config changes.

lssrc -s sshd
sshd -t
tail /var/adm/messages

Step-by-Step Diagnosis

Run sshd in debug and inspect PAM/login.cfg attributes.

sshd -ddd -p 2222 &
lssec -f /etc/security/login.cfg -s default -a auth_type
cat /etc/pam.conf

Solution – Primary Fix

Restore a tested sshd_config and PAM stack, then restart sshd.

cp -p sshd_config.good /etc/ssh/sshd_config
stopsrc -s sshd
startsrc -s sshd

Solution – Alternative Approaches

Switch to SAK-style classic auth or temporarily use telnetd over isolated network for recovery.

Verification & Acceptance Criteria

Users log in successfully and lssrc shows sshd active.

lssrc -s sshd
ssh user@host
tail /var/adm/messages

Rollback Plan

Revert to the previous sshd_config or PAM stack if regressions appear.

cp -p sshd_config.bak /etc/ssh/sshd_config
stopsrc -s sshd
startsrc -s sshd

Prevention & Hardening

Version-control /etc/ssh and /etc/pam.conf, and validate with sshd -t before restart.

Related Errors & Cross-Refs

Related to login.cfg lockouts, audit failures, and LDAP auth errors.

Related tutorial: View the step-by-step tutorial for aix-7.3.

View all aix-7.3 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

IBM AIX 7.3 OpenSSH and PAM configuration documentation.