+you can set and what kinds of files go in them. In general, the
+default for these options is expressed in terms of ‘${prefix}’, so that
+specifying just ‘--prefix’ will affect all of the other directory
+specifications.
+
+ The most portable way to affect installation locations is to pass the
+correct locations to ‘configure’; however, many packages provide one or
+both of the following shortcuts of passing variable assignments to the
+‘make install’ command line to change installation locations without
+having to reconfigure or recompile.
+
+ The first method involves providing an override variable for each
+affected directory. For example, `make install
+prefix=/path/to/alternate' will choose an alternate location, as well as
+influencing all other directory configuration variables that were
+expressed in terms of ‘${prefix}’ (or, put another way, all directories
+specified during ‘configure’ but not in terms of the common prefix must
+each be overridden at install time for the entire installation to be
+relocated). The approach of makefile variable overrides for each
+directory variable is required by the GNU Coding Standards, and ideally
+causes no recompilation. However, some platforms have known
+limitations with the semantics of shared libraries that end up
+requiring recompilation when using this method, particularly noticeable
+in packages that use GNU Libtool.
+
+ The second method involves providing the ‘DESTDIR’ variable. For
+example, ‘make install DESTDIR=/path/to/alternate’ will prepend
+‘/path/to/alternate’ before all installation paths. The approach of
+‘DESTDIR’ overrides is not required by the GNU Coding Standards, and
+does not work on platforms that have drive letters. On the other hand,
+it does better at avoiding recompilation issues, and works well even
+when some directory options were not specified in terms of ‘${prefix}’
+at ‘configure’ time. For packages which support ‘DESTDIR’, the
+variable should remain undefined during ‘configure’ and ‘make all’, and
+only be specified during ‘make install’.
+
+Optional Features
+=================