slim down docker container, doing everything in prepare.yml

molecule/generic_files/Dockerfile.j2

@@ -1,14 +1,10 @@
 # Molecule managed
 
-{% if item.registry is defined %}
-FROM {{ item.registry.url }}/{{ item.image }}
-{% else %}
 FROM {{ item.image }}
-{% endif %}
 
-RUN if [ $(command -v apt-get) ]; then apt-get update && apt-get install -y python sudo bash ca-certificates cron iputils-ping openssh-client openssh-server && apt-get clean; \
+RUN if [ $(command -v apt-get) ]; then apt-get update && apt-get install -y python sudo bash ca-certificates && apt-get clean; \
     elif [ $(command -v dnf) ]; then dnf makecache && dnf --assumeyes install python sudo python-devel python2-dnf bash && dnf clean all; \
-    elif [ $(command -v yum) ]; then yum makecache fast && yum install -y python sudo yum-plugin-ovl bash anacron iputils openssh-clients openssh-server && sed -i 's/plugins=0/plugins=1/g' /etc/yum.conf && yum clean all; \
+    elif [ $(command -v yum) ]; then yum makecache fast && yum install -y python sudo yum-plugin-ovl bash && sed -i 's/plugins=0/plugins=1/g' /etc/yum.conf && yum clean all; \
     elif [ $(command -v zypper) ]; then zypper refresh && zypper install -y python sudo bash python-xml && zypper clean -a; \
     elif [ $(command -v apk) ]; then apk update && apk add --no-cache python sudo bash ca-certificates; \
     elif [ $(command -v xbps-install) ]; then xbps-install -Syu && xbps-install -y python sudo bash ca-certificates && xbps-remove -O; fi

molecule/generic_files/prepare.yml

@@ -1,17 +1,41 @@
 ---
-- name: prepare servers - Debian only
+- name: prepare debian-based systems
-  hosts: borgbackup_servers
+  hosts: all:!centos
-  gather_facts: true
+  gather_facts: false
   tasks:
+    - name: install required packages
+      apt:
+        name:
+          - bash
+          - ca-certificates
+          - cron
+          - iputils-ping
+          - openssh-client
+
+- name: prepare centos-based systems
+  hosts: centos
+  gather_facts: false
+  tasks:
+    - name: install required packages
+      yum:
+        name:
+          - anacron
+          - iputils
+          - openssh-clients
+
+- name: prepare debian-based backupservers
+  hosts: borgbackup_servers
+  gather_facts: false
+  tasks:
+    - name: install required packages
+      apt:
+        name:
+          - openssh-server
     - name: start ssh - Debian Server
       command: service ssh start
-# note: https://forums.docker.com/t/any-simple-and-safe-way-to-start-services-on-centos7-systemd/5695/8
-# needs to be implemented
-#   - name: start sshd
-#     command: service sshd start
 
-- name: prepare all
+- name: prepare lamp
-  hosts: all:!borgbackup_servers:!centos
+  hosts: lamp
   tasks:
     - name: Install required packages
       apt: