UNIX and Linux System Administration Handbook, 5th Edition

10

Logging

System daemons, the kernel, and custom applications all emit operational data that is logged and eventually ends up on your finite-sized disks. This data has a limited useful life and may need to be summarized, filtered, searched, analyzed, compressed, and archived before it is eventually discarded. Access and audit logs may need to be managed closely according to regulatory retention rules or site security policies.

A log message is usually a line of text with a few properties attached, including a time stamp, the type and severity of the event, and a process name and ID (PID). The message itself can range from an ...