feat: update docs

docs/munin.md

@@ -2,16 +2,30 @@
 
 All nf-core pipelines have been successfully configured for use on the MUNIN cluster.
 
+## Usage
+
 To use, run the pipeline with `-profile munin`.
+
 This will download and launch the [`munin.config`](../conf/munin.config) which has been pre-configured with a setup suitable for the MUNIN cluster.
-Using this profile, a docker image containing all of the required software will be downloaded, and converted to a Singularity image before execution of the pipeline.
 
 Example: `nextflow run -profile munin`
 
-## Docker
+### Singularity
+
+This is the default behavior of this configuration profile.
+
+Using this profile, if no singularity image are available, one will be downloaded from dockerhub, and converted to a Singularity image before execution of the pipeline.
+
+It is also possible to specify the singularity profile:
+
+Example: `nextflow run -profile munin,singularity`
+
+### Docker
 
 It is also possible to execute the pipeline using Docker.
 
+Using this profile, if no docker image are available, one will be downloaded from dockerhub before execution of the pipeline.
+
 Example: `nextflow run -profile munin,docker`
 
 ## Below are non-mandatory information on iGenomes specific configuration