local0local7

Local0 through Local7 are facilities in the syslog protocol used for local, application-defined logging. They are part of the standard set of facilities that categorize log messages, allowing administrators to route and manage logs from diverse applications without colliding with system or standard service categories. Local0 to Local7 provide eight distinct channels for messages generated by local processes or custom subsystems.

In the facility field of a syslog message, Local0 maps to a numeric code (Local0 = 16) and Local7 to (Local7 = 23). These codes enable log servers and clients to filter, forward, or store messages based on their origin within the local environment. Because the content and purpose of local facilities are defined by the administrator or application, they are particularly useful for separating application logs from system logs or for grouping related components.

Usage examples include directing a web application’s logs to a dedicated file or remote destination via local0, while a database subsystem might use local1, and a background task processor local2. Modern syslog implementations, such as rsyslog, syslog-ng, and systemd-journald, support local facilities and allow configuration rules like local0. to route messages to specific files or destinations.

Configuration typically involves assigning a facility to messages produced by a given application and then creating appropriate logging rules. It is common practice to assign a separate local facility to each major subsystem, aiding in log management, analysis, and troubleshooting. Since severity remains separate from the facility, administrators can combine any facility with any priority level for flexible logging.