varlibchronydrift

Varlibchronydrift refers to the drift file used by the chronyd time synchronization service to store the estimated frequency drift of the system clock. In practice, this file holds the clock’s drift rate, which is the rate at which the local oscillator diverges from true time. Chronyd reads this value on startup to initialize its estimates and uses or updates it during operation to improve the speed and accuracy of synchronization.

Location and format often vary by distribution and configuration. The drift file is commonly located under /var/lib/chrony and may be named drift or chrony.drift, depending on the installation. The exact path is determined by the driftfile directive in chrony.conf. The file is a plain-text, single numeric value, representing the clock’s drift rate in parts per million (ppm). A positive value indicates the local oscillator runs fast relative to true time, while a negative value indicates it runs slow. The value is updated periodically by chronyd as it measures the clock against reference time sources.

Importance and usage: The drift value helps chronyd discipline the system clock, especially after startup or when network time sources become temporarily unavailable. Persisting the drift estimate across reboots allows quicker convergence when chronyd restarts, reducing the time needed to reach accurate synchronization.

Maintenance: The drift file is managed automatically by chronyd. Direct edits are generally discouraged. If the file becomes corrupted or is deleted, chronyd will recreate it and recalibrate over time. Regular backups of configuration files are recommended, but the drift file itself is typically transient data.