There are some more things you have to take into account when you create a port. This section explains the most common of those.
If your port installs one or more shared libraries, define a INSTALLS_SHLIB make variable, which will instruct a bsd.port.mk to run ${LDCONFIG} -m on the directory where the new library is installed (usually PREFIX/lib) during post-install target to register it into the shared library cache. This variable, when defined, will also facilitate addition of an appropriate @exec /sbin/ldconfig -m and @unexec /sbin/ldconfig -R pair into your pkg-plist file, so that a user who installed the package can start using the shared library immediately and de-installation will not cause the system to still believe the library is there.
If you need, you can override the default location where the new library is installed by defining the LDCONFIG_DIRS make variable, which should contain a list of directories into which shared libraries are to be installed. For example if your port installs shared libraries into PREFIX/lib/foo and PREFIX/lib/bar directories you could use the following in your Makefile:
INSTALLS_SHLIB= yes LDCONFIG_DIRS= %%PREFIX%%/lib/foo %%PREFIX%%/lib/bar
Remember that non-standard directories will not be passed to ldconfig(8) on (re-)boot! If any port really needs this to work, install a startup-script as x11/kdelibs3 does. Please double-check, often this is not necessary at all or can be avoided through -rpath or setting LD_RUN_PATH during linking (see lang/moscow_ml for an example), or through a shell-wrapper which sets LD_LIBRARY_PATH before invoking the binary, like www/mozilla does.
Note that content of LDCONFIG_DIRS is passed through sed(1) just like the rest of pkg-plist, so PLIST_SUB substitutions also apply here. It is recommended that you use %%PREFIX%% for PREFIX, %%LOCALBASE%% for LOCALBASE and %%X11BASE%% for X11BASE.
Try to keep shared library version numbers in the libfoo.so.0 format. Our runtime linker only cares for the major (first) number.
When the major library version number increments in the update to the new port version, all other ports that link to the affected library should have their PORTREVISION incremented, to force recompilation with the new library version.
If the port installs shared libraries with long version numbers, e.g. libfoo.so.0.2.9, the ports infrastructure will try to rename the files. Define NO_FILTER_SHLIBS to disable this functionality.