CentOS Stream 10 – Common Problem 097 – 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

sshd refuses keys after policy hardening on CentOS Stream 10 disrupts services and slows incident response until the root cause is resolved.

Environment & Reproduction

Crypto-policies update to FUTURE breaks legacy ssh-rsa keys for service automation.

sshd -T | grep -i pubkey
update-crypto-policies --show
grep -i rsa /etc/ssh/sshd_config

Root Cause Analysis

Misalignment between auth configuration and CentOS Stream 10 defaults causes the failure path described above.

Quick Triage

Confirm package state, service status, and recent changes before deeper diagnostics.

systemctl status
rpm -qa | grep -i 
journalctl -p err -b --no-pager | tail -100

Step-by-Step Diagnosis

Capture detailed logs, configuration deltas, and runtime state to isolate the failing component.

ssh -vvv user@host
journalctl -u sshd -n 100
update-crypto-policies --show

Solution – Primary Fix

Apply the targeted configuration change and restart the relevant services to restore expected behavior.

sudo update-crypto-policies --set DEFAULT
sudo sshd -t && sudo systemctl restart sshd
sudo ssh-keygen -lf /etc/ssh/ssh_host_ed25519_key.pub

Solution – Alternative Approaches

Re-key automation accounts to ed25519 and retire ssh-rsa fully.

Verification & Acceptance Criteria

Validate the fix with deterministic checks and ensure no regressions in dependent services.

ssh user@host true
ssh-keygen -lf ~/.ssh/id_.pub

Rollback Plan

Revert configuration and restart services to return to the previous known-good state.

update-crypto-policies --set FUTURE
systemctl restart sshd

Prevention & Hardening

Inventory key types and run crypto-policies in a staged rollout.

Related Errors & Cross-Refs

Related: crypto-policies, ssh-rsa, ed25519; see also adjacent topics in the CentOS Stream 10 common problems series.

Related tutorial: View the step-by-step tutorial for centos-stream-10.

View all centos-stream-10 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

CentOS Stream documentation, Red Hat upstream guides, and CentOS Stream 10 release notes covering this subsystem.