Syslog is an operating system administrative logging tool, and provides valuable information for use in system management and security auditing. Most suited to medium and large sites, syslog provides filtering tools that allow messages to be routed by type and severity. On UNIX/Linux systems, the file /etc/syslog.conf defines this routing configuration; on Microsoft Windows, all messages are sent to the Event Log. For more information on syslog facilities, severity levels, and how to set up a syslog.conf file, see <a href="@syslog_conf">UNIX/Linux syslog.conf</a> and PHP's <a href="@php_openlog">openlog</a> and <a href="@php_syslog">syslog</a> functions.