The file `mk.conf` is the central configuration file for everything that has to do with building software. It is used by the BSD-style `Makefiles` in `/usr/share/mk` and especially by pkgsrc. Usually, it is found in the `/etc` directory. If it doesn't exist there, feel free to create it.

Because all configuration takes place in a single file, there are some variables so the user can choose different configurations based on whether he is building the base system or packages from pkgsrc. These variables are:

* `BSD_PKG_MK`: Defined when a pkgsrc package is built.
* `BUILDING_HTDOCS`: Defined when the NetBSD web site is built.
* None of the above: When the base system is built. The file /usr/share/mk/bsd.README is a good place to start in this case. 

A typical `mk.conf` file would look like this:
<pre><code>
# This is /etc/mk.conf
#

.if defined(BSD_PKG_MK) || defined(BUILDING_HTDOCS)
# The following lines apply to both pkgsrc and htdocs.

#...
LOCALBASE=          /usr/pkg
#...

.else
# The following lines apply to the base system.

WARNS= 4

.endif
</code></pre>