In genToo your make.conf file located in /etc/make.conf is used by portAge as its primary source of information on how to setup your system. Within your make.conf file you will find a host of options that will determine what and how your system will function.
These flags tell the compiler what type of system you are using along with any optimizations you would like to include. For example a typical AMD64 setup may look like so:
CFLAGS="-march=athlon64 -O2 -pipe"
This variable is set during install and should only be edited if you know what you are doing. It tells the computer what architecture you are running.
This variable is generally set to mirror your CFLAGS setting, but can be set differently, again, if you know what you are doing.
This option tells the complier how many simultaneous threads it can compile at one time. Thus it usually set at your processor plus one. So for a single core processor:
This setting tells portage which servers it can search for the programs you wish to install.
This option tells portage which server to use in order to sync itself. After syncing portage will then know what the latest version of each file is and have an update collection of ebuilds to build packages with.
This is the variable for which Gentoo is famous. Here you tell what settings you like to take effect system wide. For a fresh install which will eventually use Gnome, a good example would be:
USE="gtk gnome X alsa cdr dvd"
This variable is used by portage so when emerging X it knows which drivers to pull in. If you had an nVidia card for example:
This variable again is used by portage in order to know which packages it needs to pull in while emerge X. A typical setup would look like:
The above list only included options that standard to every make.conf file. There are naturally other options that you can include in your make.conf to further refine your system.
The variable allows you to enable and disable various features of portage that are not enabled or disabled by default.
This option allows you to set which options you would want portage to always use when issuing a command. For example if you want portage to always run in verbose mode: