Ubuntu 14.04 LTS SSH login fails with Permission denied publickey

📖 ~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

Administrators lose key-based remote access, interrupting incident response and automation tasks.

Environment & Reproduction

Frequently appears after user migration, backup restore, or SSH hardening updates.

Root Cause Analysis

StrictModes rejects insecure file permissions or missing authorized key entries.

Quick Triage

Review sshd logs for explicit denial reason and validate account shell/home configuration.

Step-by-Step Diagnosis

Audit permissions for home, .ssh, and authorized_keys, then inspect sshd_config directives.

Solution – Primary Fix

Set correct ownership and modes, restore key material, and reload SSH daemon safely.

Solution – Alternative Approaches

Enable temporary console access or password login while restoring compliant key setup.

Verification & Acceptance Criteria

Public key authentication succeeds and logs show Accepted publickey events for target users.

Rollback Plan

Reapply previous SSH configuration backup if policy updates block all remote access.

Prevention & Hardening

Automate account provisioning checks and monitor SSH auth failures centrally.

Related Errors & Cross-Refs

Authentication refused bad ownership, invalid user, and host key mismatch warnings.

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

OpenSSH hardening and Ubuntu server authentication troubleshooting resources.