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OpenSSL Cookbook: Create a Self-Signed Cert With SAN, Inspect Expiry, Verify Chains and Fingerprints

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Self-Hosting & Infra intermediate 5 min read $0.01 Updated 2026-10-20

Tested OpenSSL commands for a local-development certificate: req -x509 with subjectAltName, x509 -text fields, openssl verify with and without -CAfile, expiry checks, fingerprints and the s_client inspection pattern.

Generate a throwaway certificate that modern clients accept, read its subject, SAN and expiry, verify it against a CA file, and compute a SHA-256 fingerprint.

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#openssl#tls#certificates#security#linux

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