Ubuntu 22.04 LTS SSH Service Fails After Host Key Permission Change

📖 ~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

OpenSSH daemon does not start, preventing remote login and automation access.

Environment & Reproduction

Seen after manual key copy or incorrect chmod on Ubuntu 22.04 LTS.

Root Cause Analysis

sshd enforces strict private host key permissions and ownership requirements.

Quick Triage

Inspect /etc/ssh host key file modes and owner/group quickly.

Step-by-Step Diagnosis

Read ssh service journal and validate sshd config syntax.

Solution – Primary Fix

Reset host key ownership and mode, then restart ssh service.

Solution – Alternative Approaches

Regenerate host keys if corruption or mismatch is suspected.

Verification & Acceptance Criteria

ssh.service is active and inbound SSH handshake completes from trusted client.

Rollback Plan

Restore prior host keys from secure backup if regenerated keys break trust model.

Prevention & Hardening

Apply configuration management to preserve correct key modes during deployments.

Related Errors & Cross-Refs

Related to sshd_config syntax issues and accidental permission changes in /etc/ssh.

Related tutorial: View the step-by-step tutorial for Ubuntu 22.04 LTS.

View all Ubuntu 22.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Review man sshd, man sshd_config, and Ubuntu OpenSSH server docs.