The file /etc/make.conf specifies all the defaults that make should use when building programs. Any changes in here will reflect globally, and specific changes can be very handy if you're going to be using the same options on a lot of builds. For example, adding
to your make.conf will mean that if a port that you're building can be made without X11 options, it will be -- very handy for a headless_server. Note that in FreeBSD 7 and above the packages that are compiled moved from make.conf to src.conf. View the man page for src.conf for more information.
Following the tip from [this page], I added the lines
SUP_UPDATE=yes SUP= /usr/local/bin/cvsup # override default `csup` in base SUPFLAGS= -g -L 2 SUPHOST= cvsupX.us.freebsd.org SUPFILE= /usr/share/examples/cvsup/standard-supfile PORTSSUPFILE= /usr/share/examples/cvsup/ports-supfile
to my make.conf, I was able to go into /usr/ports and type in
# make update
and update all my ports. Likewise, I can go into /usr/src and run the same command and update all my system sources.
You can see what options are available to you in /usr/share/examples/etc/make.conf
Note that you can also set compiler settings (for you Gentoo Linux expatriates) and CPU architecture in make.conf.