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