ntp_checker

ntp_checker (also known as Timewatch) is a monitoring tool that ensures the accuracy of internal Network Time Protocol (NTP) servers. It compares their time offsets against a trusted external reference, such as the UK's National Physical Laboratory (NPL), and generates alerts if discrepancies exceed a configurable threshold. This helps maintain time synchronization across network infrastructure, which is critical for logging, security, and operational consistency.

Key Features

• Offset Monitoring — Compares internal NTP server offsets against an external reference (NPL or PTB) and logs warnings if the difference exceeds a defined limit.
• Alert Management — Sends email alerts for new warnings and appends subsequent warnings to a log without spamming; warnings are archived after 7 days.
• Log Rotation — Automatically deletes logs older than 28 days and renames warning files with a date stamp after 7 days.
• Visualization Integration — Evolved into Timewatch with InfluxDB and Grafana for data storage and visualization of NTP offset trends.
• Fault Tolerance — Uses a secondary reference server (PTB) if the primary (NPL) is unavailable and includes flocking to prevent multiple script instances.
• Extended Monitoring — Optional checks for permitted reference clocks and supports SNMP traps for integration with network monitoring systems.

Philosophy

The project emphasizes reliability and minimal alert noise, ensuring administrators are notified of genuine time synchronization issues without being overwhelmed by transient network glitches.