docs: add charliecloud + docker verbage
@@ -2,7 +2,9 @@ The Charliecloud container runtime requires enabling the user namespaces mapping
option. This allows applications to run with root privilege inside a container,
but have them run as a different, typically non-privileged, user on the host.
Though generally regarded as mature and safe, CentOS considers this a Technology
-Preview, so it must be manually enabled with kernel arguments.
+Preview, so it must be manually enabled with kernel arguments. We demonstrate
+enabling on compute nodes, but it would also be required on the SMS if you wish
+to build and run containers there.
% begin_ohpc_run
% ohpc_validation_newline
@@ -17,3 +19,15 @@ Preview, so it must be manually enabled with kernel arguments.
[sms](*\#*) wwvnfs --chroot $CHROOT
\end{lstlisting}
% end_ohpc_run
+
+\begin{center}
+\begin{tcolorbox}[]
+\small
+Typical Charliecloud workflows are based around Docker containers, but it is not
+strictly necessary to install Docker itself on the HPC resource. A common
+pattern is to build the Docker container on a laptop or VM and upload the result
+to the cluster for use with Charliecloud. More information can be found at
+\href{https://hpc.github.io/charliecloud/}
+ {\color{blue}{https://hpc.github.io/charliecloud/}}
+\end{tcolorbox}
+\end{center}
