configtest

Configtest is a term used to describe a utility or command that checks the syntax and basic validity of a program’s configuration files without fully starting the service. It is provided by a range of software systems to detect syntax errors, misspelled directives, incorrect values, or missing included files before changes are applied.

Operation and purpose: A configtest typically parses the configuration, resolves includes and references, and reports any errors with file names and line numbers. Depending on the software, it may load the configuration into a temporary process or namespace, perform minimal initialization, and exit with a nonzero status on errors. The main goal is to prevent applying broken configurations that could cause service downtime when reloading or restarting.

Common usage: In practice, admins run a configtest after editing a configuration file and before reloading or restarting the service. A successful test usually prints a confirmation that the configuration file appears to be valid. For example, Apache HTTP Server supports commands such as apachectl configtest or httpd -t to verify syntax and configuration integrity. If issues are found, the tool provides error messages indicating the problematic file and line to guide corrections.

Limitations: A configtest does not guarantee that the configuration will function correctly under all runtime conditions, nor does it catch issues related to external resources, permissions, or plugin behavior that only emerge during operation. Some tests may require specific privileges or environment settings to fully evaluate all references.

See also: configuration validation, dry run, linting, syntax checking.