Merge branch 'singularity' into 'master'

Minor instruction improvements for Singularity example

Closes #2

See merge request !6

singularity/README.md

@@ -23,6 +23,9 @@ singularity run sl.simg
 
 ## Things to Note
 
+- In order to build a singularity image, you need to be a member of the `singulars` group on juseless.
+  You can check this with the `groups` command on juseless - if `singulars` shows up, you're good.
+  Please contact [Alex or Jan](https://www.fz-juelich.de/inm/inm-7/EN/Forschung/Data%20and%20Platforms/_node.html) if you need to be added to this group.
 - Please note that in this example the singularity container is built on a
   compute node. This is convenient, because it allows for the job to be
   completed faster. More on this can be found in the **Further Reading** section
@@ -31,6 +34,18 @@ singularity run sl.simg
   request machines with faster scratch disks (it'll prefer, but not require
   these machines to be used).
 
+## Things to Adjust
+
+This example is entirely self contained and can be used to build a toy example container.
+In order to build a custom container, adjust the Definition file `.def` to your needs.
+More information on how to write a Singularity Definition file can be found [here](https://sylabs.io/guides/3.6/user-guide/definition_files.html)
+
+In order to build the singularity image from `sl.def`, your repository will be cloned to a temporary location on the compute node.
+Please adjust the `git clone` call in `singularity.sh` to point to your clone of `htcondor-templates` on juseless (in which you have adjusted your `.def` file) instead of the original template from JuGit.
+
+This example assumes that it is located in `~/htcondor-templates/singularity`.
+If you have cloned it elsewhere, adjust the submit file as necessary.
+
 ## Further Reading
 
 Juseless is a collection of systems. The most important ones are the head node
@@ -48,9 +63,3 @@ write a lot. Local disk are faster than the network, so it's a win all around.
 
 Compute jobs see this *scratch disk* as `/tmp`. Read the docs linked above for
 more detailed information.
-
-## Prerequisites
-This example assumes that it is located in `~/htcondor-templates/singularity`.
-If you have cloned it elsewhere, adjust the submit file as necessary.
-
-Otherwise, this example is entirely self contained.

singularity/singularity.sh

 #!/bin/bash
 
 # clone the repo (with the singularity recipe file) to the scratch disk
+# adjust the command to point to your clone, e.g.
+# "git clone /data/project/llamas/htcondor-templates.git /tmp/htcondor-templates"
 git clone https://jugit.fz-juelich.de/inm7/tools/htcondor-templates.git /tmp/htcondor-templates
 cd /tmp/htcondor-templates/singularity