[web] Added docs on Docker usage.

web/content/docs/userguide/basics/container.md

@@ -81,3 +81,31 @@ Singularity ogs-6.2.2-serial.sif:...> exit
 * `singularity exec --app ogs ogs-xxx-gui-xxx.sif DataExplorer`
 
 You may use this container on e.g. `envinf1` with X11 forwarding (`ssh -XY envinf1`).
+
+----
+
+## With Docker
+
+Although Singularity is the preferred container runtime you can use [Docker](https://www.docker.com) too.
+
+### Prerequisites
+
+* A running [installation of Docker](https://docs.docker.com/get-docker/)
+
+### Run OGS inside a Docker container
+
+* Get the container: `docker pull registry.opengeosys.org/ogs/ogs/ogs-serial`
+* Start interactive container session: `docker run --rm -it registry.opengeosys.org/ogs/ogs/ogs-serial`
+* Run ogs: `/scif/apps/ogs/bin/ogs --version`
+* Exit the container: `exit`
+
+You will notice that the interactive session in your container is isolated from your host, i.e. you do not have access to files on your host. You need to explicitly [mount](https://docs.docker.com/storage/bind-mounts/) them on `docker run`:
+
+```bash
+mkdir ~/ogs_out
+docker run --rm -it -v $HOME/code/ogs6/ogs/Tests/Data:/tmp/data:ro -v $HOME/ogs_out:/tmp/out registry.opengeosys.org/ogs/ogs/ogs-seria
+/scif/apps/ogs/bin/ogs -o /tmp/out /tmp/data/Elliptic/cube_1x1x1_SteadyStateDiffusion/cube_1e4.prj
+exit
+ls ~/ogs_out
+# [shows ogs generated output files]
+```