diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f17cd1c..17340e8 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,20 +1,54 @@
+.build_docker:
+
+  image: 'docker:19.03.11'
+  services:
+    - docker:19.03.11-dind
+  variables:
+    # Use TLS https://docs.gitlab.com/ee/ci/docker/using_docker_build.html#tls-enabled
+    DOCKER_HOST: tcp://docker:2376
+    DOCKER_TLS_CERTDIR: "/certs"
+  stage: .pre
+  before_script:
+  - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
+  script:
+    - echo ${DOCKERFILE}
+    - cd ${DOCKERFILE}
+    - docker build -t ${DOCKERREPO} .
+    - docker push ${DOCKERREPO}
+  
+  when: manual
+
+
+docker build:debian_bullseye:
+  extends: .build_docker
+  variables:
+   DOCKERFILE: dockerfiles/debian:bullseye/
+   DOCKERREPO: registry.gitlab.com/ganciaux/slides:debian_bullseye
+
+docker build:ubuntu_20_04:
+  extends: .build_docker
+  variables:
+   DOCKERFILE: dockerfiles/ubuntu:20.04/
+   DOCKERREPO: registry.gitlab.com/ganciaux/slides:ubuntu_20_04
+
+
 .tests:
   stage: test
 
   script:
     - python3 setup.py install
     - cd tests
     - pytest --junitxml=report.xml
   artifacts:
     reports:
       junit: tests/report.xml
 
-test:ubuntu_18_04:
-  image: registry.gitlab.com/ganciaux/slides:ubuntu_18_04
-  extends:
-    - .tests
+# test:ubuntu_20_04:
+#   image: registry.gitlab.com/ganciaux/slides:ubuntu_20_04
+#   extends:
+#     - .tests
 
-test:ubuntu_19_10:
-  image: registry.gitlab.com/ganciaux/slides:ubuntu_19_10
+test:debian_bullseye:
+  image: registry.gitlab.com/ganciaux/slides:debian_bullseye
   extends:
     - .tests
diff --git a/dockerfiles/ubuntu:18.04/Dockerfile b/dockerfiles/debian:bullseye/Dockerfile
similarity index 96%
rename from dockerfiles/ubuntu:18.04/Dockerfile
rename to dockerfiles/debian:bullseye/Dockerfile
index 87b1891..e702462 100644
--- a/dockerfiles/ubuntu:18.04/Dockerfile
+++ b/dockerfiles/debian:bullseye/Dockerfile
@@ -1,18 +1,18 @@
-FROM ubuntu:18.04
+FROM debian:bullseye
 MAINTAINER Guillaume Anciaux <guillaume.anciaux@epfl.ch>
 
 
 ENV LANG C.UTF-8
 ENV LC_ALL C.UTF-8
 
 ## for apt to be noninteractive
 ENV DEBIAN_FRONTEND noninteractive
 ENV DEBCONF_NONINTERACTIVE_SEEN true
 
 # minimal dependencies
 RUN apt-get -qq update && apt-get install -y python3-pip texlive-latex-extra clang-format libmagickwand-dev dvipng && rm -rf /var/lib/apt/lists/*
 RUN pip3 install jupyter sympy pypdf2 matplotlib wand dill jupyter_contrib_nbextensions pyparsing>=2.3.0
 
 # for testing 
 RUN apt-get -qq update && apt-get install -y python3-pep8  && rm -rf /var/lib/apt/lists/*
 RUN pip3 install pytest
diff --git a/dockerfiles/ubuntu:19.10/Dockerfile b/dockerfiles/ubuntu:20.04/Dockerfile
similarity index 59%
rename from dockerfiles/ubuntu:19.10/Dockerfile
rename to dockerfiles/ubuntu:20.04/Dockerfile
index 67f629b..bba54a5 100644
--- a/dockerfiles/ubuntu:19.10/Dockerfile
+++ b/dockerfiles/ubuntu:20.04/Dockerfile
@@ -1,18 +1,18 @@
-FROM ubuntu:19.10
+FROM ubuntu:20.04
 MAINTAINER Guillaume Anciaux <guillaume.anciaux@epfl.ch>
 
 
 ENV LANG C.UTF-8
 ENV LC_ALL C.UTF-8
 
 ## for apt to be noninteractive
 ENV DEBIAN_FRONTEND noninteractive
 ENV DEBCONF_NONINTERACTIVE_SEEN true
 
 # minimal dependencies
-RUN apt-get -qq update && apt-get install -y python3-pip texlive-latex-extra clang-format libmagickwand-dev dvipng && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt install -y python3-pip texlive-latex-extra clang-format libmagickwand-dev dvipng && rm -rf /var/lib/apt/lists/*
 RUN pip3 install jupyter sympy pypdf2 matplotlib wand dill jupyter_contrib_nbextensions pyparsing>=2.3.0
 
 # for testing 
-RUN apt-get -qq update && apt-get install -y python3-pep8  && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install -y python3-pep8  && rm -rf /var/lib/apt/lists/*
 RUN pip3 install pytest