diff --git a/03-gitlab-CI.md b/03-gitlab-CI.md
index a02c90a0600365b9841e1449e51ec485c4638a7f..5367b0567d551d36cbd086f67979905c493a8b7c 100644
--- a/03-gitlab-CI.md
+++ b/03-gitlab-CI.md
@@ -34,6 +34,48 @@ build:
 - tags added: latest, YYYY-MM-DD-hhmm, short-hash, long-hash
 - `singularity build my.sif docker://registry-gitlab.pasteur.fr/tru/conda-container-howto:latest`
 - https://gitlab.pasteur.fr/tru/conda-container-howto/container_registry
+  copy the tag you want (`registry-gitlab.pasteur.fr/tru/conda-container-howto:2021-09-23-1139` for instance)
+```
+[tru@maestro-submit ~]$ module add singularity
+[tru@maestro-submit ~]$ singularity build /tmp/a.sif docker://registry-gitlab.pasteur.fr/tru/conda-container-howto:2021-09-23-1139
+INFO:    Starting build...
+Getting image source signatures
+Copying blob 2d473b07cdd5 skipped: already exists  
+Copying blob 1a591a021b37 done  
+Copying blob c0c3ff4ea0d5 done  
+Copying blob f475f673d1f0 done  
+Copying blob 1d12568db87c done  
+Copying blob 8cffb3effd95 done  
+Copying config 5df04f53b9 done  
+Writing manifest to image destination
+Storing signatures
+2021/09/23 13:54:05  info unpack layer: sha256:2d473b07cdd5f0912cd6f1a703352c82b512407db6b05b43f2553732b55df3bc
+2021/09/23 13:54:05  warn rootless{usr/bin/newgidmap} ignoring (usually) harmless EPERM on setxattr "security.capability"
+2021/09/23 13:54:05  warn rootless{usr/bin/newuidmap} ignoring (usually) harmless EPERM on setxattr "security.capability"
+2021/09/23 13:54:05  warn rootless{usr/bin/ping} ignoring (usually) harmless EPERM on setxattr "security.capability"
+2021/09/23 13:54:06  warn rootless{usr/sbin/arping} ignoring (usually) harmless EPERM on setxattr "security.capability"
+2021/09/23 13:54:06  warn rootless{usr/sbin/clockdiff} ignoring (usually) harmless EPERM on setxattr "security.capability"
+2021/09/23 13:54:07  info unpack layer: sha256:1a591a021b375badfbf07a5fbc46f8f3728b288d4751d6462642d8ef970617a6
+2021/09/23 13:54:09  info unpack layer: sha256:c0c3ff4ea0d56b1bb372924a319e38dd84d9d67b5546d654879389695e6e9d49
+2021/09/23 13:54:12  info unpack layer: sha256:f475f673d1f0e77984309c350c33441362a867c129b93a6ca20f03f7c70d8155
+2021/09/23 13:54:14  info unpack layer: sha256:1d12568db87cb741f1e918e9c4ac49eaeeb3a8fc98e6c71247ba778e9d2dad3d
+2021/09/23 13:54:14  info unpack layer: sha256:8cffb3effd95583812204a146f5aeaad07d3911c5e1c30a9280d182d501baff3
+INFO:    Creating SIF file...
+INFO:    Build complete: /tmp/a.sif
+[tru@maestro-submit ~]$ /tmp/a.sif
+Singularity> eval "$(/opt/miniconda3/bin/conda shell.bash hook)"
+(base) Singularity> conda env list
+# conda environments:
+#
+base                  *  /opt/miniconda3
+pythonnet                /opt/miniconda3/envs/pythonnet
+
+(base) Singularity> conda activate pythonnet
+(pythonnet) Singularity> python -c 'import clr'
+(pythonnet) Singularity> type python
+python is hashed (/opt/miniconda3/envs/pythonnet/bin/python)
+<...>
+```
 
 ## Caveats
 - docker registry is rate limited