Linux Time Synchronization and NTP: chrony Configuration, Troubleshooting, and Production Practices
Overview One production incident made me take time synchronization seriously. In the middle of the night, the business team reported mass HTTPS request failures with SSL_ERROR_BAD_CERTIFICATE. We spent two hours troubleshooting—combed through network topology, firewall rules, certificate configs—nothing. Finally, someone happened to glance at the system clock: it was 12 seconds ahead of real time. Those 12 seconds made the server think client certificates hadn’t reached their notBefore time yet, so it rejected every handshake....