📖 ~1 min read
Table of contents
Symptom & Impact
Clients refuse SSH connection with host key verification errors.
Environment & Reproduction
Common after host rebuild, reprovision, or key rotation.
Root Cause Analysis
Server host key changed but clients still trust old fingerprint.
Quick Triage
Validate current host key fingerprints through trusted channel.
Step-by-Step Diagnosis
Compare old and new fingerprints in client known_hosts entries.
Solution – Primary Fix
Remove stale known_hosts record and add validated key.
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Solution – Alternative Approaches
Use SSH certificates to avoid per-host key pinning overhead.
Verification & Acceptance Criteria
SSH connects successfully with verified host identity.
Rollback Plan
Restore prior key material if unauthorized key changes are suspected.
Prevention & Hardening
Publish key rotation notices and fingerprint inventory for operators.
Related Errors & Cross-Refs
Related to man-in-the-middle alerts and stale DNS records.
Related tutorial: View the step-by-step tutorial for Debian 13.
View all Debian 13 tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
OpenSSH host key verification and key management guidance.
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