Installation directories should always be named by variables, so it is
easy to install in a nonstandard place. The standard names for these
-variables are described below. They are based on a standard filesystem
-layout; variants of it are used in SVR4, 4.4BSD, GNU/Linux, Ultrix v4,
-and other modern operating systems.
+variables and the values they should have in GNU packages are
+described below. They are based on a standard filesystem layout;
+variants of it are used in GNU/Linux and other modern operating
+systems.
+
+Installers are expected to override these values when calling
+@command{make} (e.g., @kbd{make prefix=/usr install} or
+@command{configure} (e.g., @kbd{configure --prefix=/usr}). GNU
+packages should not try to guess which value should be appropriate for
+these variables on the system they are being installed onto: use the
+default settings specified here so that all GNU packages behave
+identically, allowing the installer to achieve any desired layout.
These two variables set the root for the installation. All the other
installation directories should be subdirectories of one of these two,
programs rather than by users. This directory should normally be
@file{/usr/local/libexec}, but write it as @file{$(exec_prefix)/libexec}.
(If you are using Autoconf, write it as @samp{@@libexecdir@@}.)
+
+The definition of @samp{libexecdir} is the same for all packages, so
+you should install your data in a subdirectory thereof. Most packages
+install their data under @file{$(libexecdir)/@var{package-name}/},
+possibly within additional subdirectories thereof, such as
+@file{$(libexecdir)/@var{package-name}/@var{machine}/@var{version}}.
@end table
Data files used by the program during its execution are divided into
@item datarootdir
The root of the directory tree for read-only architecture-independent
data files. This should normally be @file{/usr/local/share}, but
-write it as @file{$(prefix)/share}. @samp{datadir}'s default value is
-based on this variable; so are @samp{infodir}, @samp{mandir}, and others.
+write it as @file{$(prefix)/share}. (If you are using Autoconf, write
+it as @samp{@@datarootdir@@}.) @samp{datadir}'s default value is
+based on this variable; so are @samp{infodir}, @samp{mandir}, and
+others.
@item datadir
The directory for installing idiosyncratic read-only
architecture-independent data files for this program. This is usually
the same place as @samp{datarootdir}, but we use the two separate
-variables so that you can move these idiosyncratic files without
+variables so that you can move these program-specific files without
altering the location for Info files, man pages, etc.
-The default definition of @samp{datadir} should be
+This should normally be @file{/usr/local/share}, but write it as
@file{$(datarootdir)}. (If you are using Autoconf, write it as
@samp{@@datadir@@}.)
+The definition of @samp{datadir} is the same for all packages, so you
+should install your data in a subdirectory thereof. Most packages
+install their data under @file{$(datadir)/@var{package-name}/}.
+
@item sysconfdir
The directory for installing read-only data files that pertain to a
single machine--that is to say, files for configuring a host. Mailer