Update Developing_LArSoft_with_Containers.md

LArSoftWiki/Developing_LArSoft_with_Containers.md

@@ -11,6 +11,19 @@ export UPS_OVERRIDE='-H Linux64bit+3.10-2.17'
 
 ```
 
+### Jenkins with apptainer
+
+For Jenkins build jobs, we start the apptainer and run the job in the same command.  The build script then must set `UPS_OVERRIDE`.
+```
+# start the container and run the build
+    /cvmfs/oasis.opensciencegrid.org/mis/apptainer/current/bin/apptainer exec \
+    --pid --ipc \
+    -B /etc/hosts,/tmp,/cvmfs/,${WORKSPACE} \
+    --pwd ${WORKSPACE} \
+    /cvmfs/singularity.opensciencegrid.org/fermilab/fnal-dev-sl7:latest /bin/bash ./larutils/buildScripts/build-larsoft.sh
+    status=$?
+```
+
 ## Docker
 
 Docker is no longer a recommended container.  However, the instructions are here for [a Docker container approach](Developing_LArSoft_on_Unsupported_Operating_Systems_with_Docker).