IBM AIX 7.2 – Common Problem 057 – 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 from client fails ‘Permission denied (publickey)’ to AIX 7.3 host.

Environment & Reproduction

OpenSSH on AIX 7.3 with stricter HostKeyAlgorithms and key permissions.

Root Cause Analysis

Modern client offers ed25519 while sshd_config restricts to RSA, or ~/.ssh perms too open.

Quick Triage

Tail /var/adm/ras/syslog.caa or /var/log/messages for sshd errors.

Step-by-Step Diagnosis

Run ssh -vvv user@host and check /etc/ssh/sshd_config on AIX.

Solution – Primary Fix

Add PubkeyAcceptedAlgorithms +ssh-rsa or generate ed25519 key.

Solution – Alternative Approaches

Use password auth temporarily via PasswordAuthentication yes.

Verification & Acceptance Criteria

ssh login succeeds with key and authlog records Accepted publickey.

Rollback Plan

Revert sshd_config from /etc/ssh/sshd_config.bak and stopsrc/startsrc sshd.

Prevention & Hardening

Standardise on ed25519 keys and audit ~/.ssh permissions (700/600).

Related Errors & Cross-Refs

sshd_config syntax errors, AIX OpenSSH version mismatch.

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 OpenSSH for AIX documentation.