diff --git a/Renv/environment.yml b/Renv/environment.yml
index eef32e1..9b09145 100644
--- a/Renv/environment.yml
+++ b/Renv/environment.yml
@@ -1,6 +1,6 @@
 name: "base"
 channels:
-  - defaults
+  - conda-forge
 # dependencies:
 # - add packages here
 # - one per line
diff --git a/aiida/Dockerfile b/aiida/Dockerfile
index 3170eae..b0259c7 100644
--- a/aiida/Dockerfile
+++ b/aiida/Dockerfile
@@ -18,7 +18,7 @@ USER ${NB_USER}
 
 # install the python dependencies
 COPY requirements.txt environment.yml /tmp/
-RUN conda env update -q -f /tmp/environment.yml
+RUN mamba env update -q -f /tmp/environment.yml
 
 # get around pyyaml upgrade error ("Cannot uninstall 'PyYAML'. It is a distutils installed project...")
 RUN /opt/conda/bin/pip install --upgrade --force-reinstall pip==9.0.3 && \
diff --git a/aiida/environment.yml b/aiida/environment.yml
index 616700c..bf9817e 100644
--- a/aiida/environment.yml
+++ b/aiida/environment.yml
@@ -1,7 +1,6 @@
 name: "base"
 channels:
   - conda-forge
-  - defaults
   - cjs14
 dependencies:
 # - aiida-core
diff --git a/desktop/Dockerfile b/desktop/Dockerfile
index 64faf24..f4acf60 100644
--- a/desktop/Dockerfile
+++ b/desktop/Dockerfile
@@ -18,7 +18,7 @@ FROM renku/renkulab-vnc:0.20.0
 
 # install the python dependencies
 COPY requirements.txt environment.yml /tmp/
-RUN conda env update -q -f /tmp/environment.yml && \
+RUN mamba env update -q -f /tmp/environment.yml && \
     /opt/conda/bin/pip install -r /tmp/requirements.txt && \
     conda clean -y --all && \
     conda env export -n "root"
diff --git a/desktop/environment.yml b/desktop/environment.yml
index a3ed1dd..71f41c5 100644
--- a/desktop/environment.yml
+++ b/desktop/environment.yml
@@ -1,6 +1,6 @@
 name: "base"
 channels:
-  - defaults
+  - conda-forge
 # dependencies:
 # - add packages here
 # - one per line
diff --git a/matlab/Dockerfile b/matlab/Dockerfile
index d2ed344..82ef472 100644
--- a/matlab/Dockerfile
+++ b/matlab/Dockerfile
@@ -18,7 +18,7 @@ FROM renku/renkulab-matlab:0.20.0
 
 # install the python dependencies
 COPY requirements.txt environment.yml /tmp/
-RUN conda env update -q -f /tmp/environment.yml && \
+RUN mamba env update -q -f /tmp/environment.yml && \
     /opt/conda/bin/pip install -r /tmp/requirements.txt && \
     conda clean -y --all && \
     conda env export -n "root"
diff --git a/matlab/environment.yml b/matlab/environment.yml
index a3ed1dd..71f41c5 100644
--- a/matlab/environment.yml
+++ b/matlab/environment.yml
@@ -1,6 +1,6 @@
 name: "base"
 channels:
-  - defaults
+  - conda-forge
 # dependencies:
 # - add packages here
 # - one per line
diff --git a/python-minimal-streamlit/Dockerfile b/python-minimal-streamlit/Dockerfile
index 0559ca5..0e3aa94 100644
--- a/python-minimal-streamlit/Dockerfile
+++ b/python-minimal-streamlit/Dockerfile
@@ -18,7 +18,7 @@ FROM renku/renkulab-py:3.10-0.20.0
 
 # install the python dependencies
 COPY requirements.txt environment.yml /tmp/
-RUN conda env update -q -f /tmp/environment.yml && \
+RUN mamba env update -q -f /tmp/environment.yml && \
     /opt/conda/bin/pip install -r /tmp/requirements.txt && \
     conda clean -y --all && \
     conda env export -n "root"
@@ -26,7 +26,7 @@ RUN conda env update -q -f /tmp/environment.yml && \
 # RENKU_VERSION determines the version of the renku CLI
 # that will be used in this image. To find the latest version,
 # visit https://pypi.org/project/renku/#history.
-ARG RENKU_VERSION={{ __renku_version__ | default("1.2.4") }}
+ARG RENKU_VERSION={{ __renku_version__ | default("2.6.2") }}
 
 # to run streamlit
 COPY jupyter_notebook_config.py ${HOME}/.jupyter/
diff --git a/python-minimal-streamlit/environment.yml b/python-minimal-streamlit/environment.yml
index 7ed80ba..582e9b1 100644
--- a/python-minimal-streamlit/environment.yml
+++ b/python-minimal-streamlit/environment.yml
@@ -1,6 +1,5 @@
 name: "base"
 channels:
-  - defaults
   - conda-forge
 dependencies:
   - pip
diff --git a/qgis/Dockerfile b/qgis/Dockerfile
index b27b471..2388e4b 100644
--- a/qgis/Dockerfile
+++ b/qgis/Dockerfile
@@ -18,7 +18,7 @@ FROM renku/renkulab-qgis:0.20.0
 
 # install the python dependencies
 COPY requirements.txt environment.yml /tmp/
-RUN conda env update -q -f /tmp/environment.yml && \
+RUN mamba env update -q -f /tmp/environment.yml && \
     /opt/conda/bin/pip install -r /tmp/requirements.txt && \
     conda clean -y --all && \
     conda env export -n "root"
diff --git a/qgis/environment.yml b/qgis/environment.yml
index a3ed1dd..71f41c5 100644
--- a/qgis/environment.yml
+++ b/qgis/environment.yml
@@ -1,6 +1,6 @@
 name: "base"
 channels:
-  - defaults
+  - conda-forge
 # dependencies:
 # - add packages here
 # - one per line