Conffile

Conffile is a term used to refer to a configuration file, typically a text file that stores settings used by a software program or system at runtime. Conffiles are commonly found in Unix-like environments and often reside under directories such as /etc. They define parameters that control how a program behaves, and they may be read when the program starts or when it reloads its configuration. Extensions like .conf are frequently used, but the exact naming is not universal.

In the context of Debian and other Debian-based distributions, conffile has a specific packaging meaning. A conffile is a configuration file that is treated specially by the package management system. Packages declare their conffiles to help the system manage upgrades; when a package is updated, the package manager can compare the existing conffile with the new version and prompt the administrator on how to proceed if local modifications are detected. This behavior aims to preserve administrator changes while still applying upstream updates.

Not all configuration files are necessarily conffiles. The designation is applied to files that are explicitly managed by the package management system as configuration data, typically those that live in /etc or other system-wide settings locations. Conffiles often contain default settings that can be overridden by local modifications, and they are expected to be stable across program updates unless the administrator actively changes them.

Beyond Debian, other systems have analogous concepts (for example, RPM’s config files). In general, conffiles play a crucial role in separating runtime configuration from program code and defaults, facilitating safer upgrades while allowing administrators to tailor behavior to their environments.