edits for upgrade discussion
@@ -62,21 +62,43 @@ rolling updates are pre-configured.
you will need to reboot the compute nodes when convenient to enable the
changes.
-Component additions are also fair game for \OHPC{} micro releases, and the 1.3.1
-release in particular includes GCC 7.1.0, along with runtimes and libraries
-compiled with that toolchain. Installation of these additions is simplified
+\subsubsection{New component variants}
+
+As newer variants of key compiler/MPI stacks are released,\OHPC{} will
+periodically add toolchains enabling the latest variant. To stay consistent
+throughout the build hierarcy, minimize recompilation requirements for existing
+binaries, and allow for multiple variants to coexist, unique delimiters are
+used to distinguish RPM package names and module hierarchy.
+
+In the case of a fresh install, \OHPC{} recipes default to installation of the
+latest toolchains available in a given release branch. However, if upgrading a
+previously installed system, adminstrators can {\em opt-in} to enable new
+variants as they become available. To illustrate this point, we use the \OHPC{}
+1.3.1 release as an example which includes a new {``gnu7''} compiler variant
+providing GCC 7.x along with runtimes and libraries compiled
+with the newer toolchain. Note that prior to the 1.3.1 release, the {``gnu''} variant was
+available which provided GCC 5.x versions.
+%Component additions are also fair game for \OHPC{} micro releases, and the 1.3.1
+%release in particular includes GCC 7.1.0, along with runtimes and libraries
+%compiled with that toolchain.
+In the case where an admin would like to enable the newer {gnu7} toolchain,
+installation of these additions is simplified
with the use of \OHPC{}'s meta-packages (see Table \ref{table:groups} in Appendix
-\ref{appendix:manifest}), and the toolchain package naming
-convention allows the new compiler to be installed concurrently with older
-versions. The following example illustrates configuring a GCC 7.1.0 default
-development environment and installing all correlated packages.
+\ref{appendix:manifest}).
+%and the toolchain package naming
+%convention allows the new compiler to be installed concurrently with older
+%versions.
+The following example illustrates adding the complete ``gnu7'' toolchain
+environment leveraging convenience meta-packages and also updates the modules environment to make it the default.
+%configuring a GCC 7.1.0 default
+%development environment and installing all correlated packages.
\begin{lstlisting}[language=bash,keywords={}]
# Update default environment
[sms](*\#*) (*\remove*) lmod-defaults-gnu-mvapich2-ohpc
[sms](*\#*) (*\install*) lmod-defaults-gnu7-mvapich2-ohpc
-# Install GCC 7.1.0-compiled meta-packages with dependencies
+# Install GCC 7.x-compiled meta-packages with dependencies
[sms](*\#*) (*\install*) ohpc-gnu7-perf-tools \
ohpc-gnu7-serial-libs \
ohpc-gnu7-io-libs \
