Some packages have build time options, usually to select between different dependencies, enable optional support for big dependencies or enable experimental features. To see which options, if any, a package supports, and which options are mutually exclusive, run make show-options, for example: The following options are supported by this package: ssl Enable SSL support. Exactly one of the following gecko options is required: firefox Use firefox as gecko rendering engine. mozilla Use mozilla as gecko rendering engine. At most one of the following database options may be selected: mysql Enable support for MySQL database. pgsql Enable support for PostgreSQL database. These options are enabled by default: firefox These options are currently enabled: mozilla ssl The following variables can be defined in /etc/mk.conf to select which options to enable for a package: PKG_DEFAULT_OPTIONS, which can be used to select or disable options for all packages that support them, and PKG_OPTIONS.pkgbase, which can be used to select or disable options specifically for package pkgbase. Options listed in these variables are selected, options preceded by - are disabled. The following settings are consulted in the order given, and the last setting that selects or disables an option is used: the default options as suggested by the package maintainer the options implied by the settings of legacy variables (see below) PKG_DEFAULT_OPTIONS PKG_OPTIONS.pkgbase For groups of mutually exclusive options, the last option selected is used, all others are automatically disabled. If an option of the group is explicitly disabled, the previously selected option, if any, is used. It is an error if no option from a required group of options is selected, and building the package will fail. Before the options framework was introduced, build options were selected by setting a variable in /etc/mk.conf for each option. To ease transition to the options framework for the user, these legacy variables are converted to the appropriate options setting automatically. A warning is issued to prompt the user to update /etc/mk.conf to use the options framework directly. Support for these legacy variables will be removed eventually.