What does the /etc/services file document?

The /etc/services file is a crucial configuration file in Unix-like operating systems, including Linux. It serves as a reference that documents the standard application services and their corresponding port numbers. Each entry in this file typically includes the service name, the corresponding port number, and the type of protocol used (either TCP or UDP).

This standardization helps applications and services to communicate reliably over the network by knowing the specific port number designated for each service. For instance, the entry for HTTP indicates that web traffic operates over port 80, and this consistency ensures that various software components can interact seamlessly.

Other options refer to aspects of system management or configuration that do not belong to the functions served by the /etc/services file. For example, log file sizes and kernel module configurations are not documented in this file, nor are system startup procedures managed through it. The focus of the /etc/services file is entirely on network ports associated with application services.