[debops.docker] Drop custom 'docker.service' unit

The 'debops.docker' role will not maintain its own custom
'docker.service' systemd unit file anymore, to avoid rapid changes in
the Docker upstream. Instead, required changes will be configured using
the unit override files.

ansible/roles/debops.docker/tasks/main.yml

@@ -20,25 +20,14 @@
     update_cache: True
   when: docker__upstream|d() | bool
 
-- name: Make sure that systemd directory exists
-  file:
-    path: '/etc/systemd/system'
-    state: 'directory'
-    owner: 'root'
-    group: 'root'
-    mode: '0755'
-  when: ansible_service_mgr == 'systemd'
-  tags: [ 'role::docker:config' ]
-
-- name: Make sure that docker.service.d directory exists
+- name: Make sure that docker.service.d override directory exists
   file:
     path: '/etc/systemd/system/docker.service.d'
     state: 'directory'
     owner: 'root'
     group: 'root'
     mode: '0755'
-  when: (ansible_service_mgr == 'systemd' and
-        (docker__env_http_proxy is defined or docker__env_https_proxy is defined))
+  when: ansible_service_mgr == 'systemd'
   tags: [ 'role::docker:config' ]
 
 - name: Remove other version if upstream is modified
@@ -156,41 +145,24 @@
   tags: [ 'role::docker:config' ]
   when: (ansible_service_mgr == 'systemd' and docker__register_version.stdout is version_compare('1.10', '>='))
 
-- name: Install Debian systemd service unit
+- name: Configure Docker systemd overrides
   template:
-    src: 'etc/systemd/system/docker.service.j2'
-    dest: '/etc/systemd/system/docker.service'
+    src: 'etc/systemd/system/docker.service.d/{{ item }}.j2'
+    dest: '/etc/systemd/system/docker.service.d/{{ item }}'
     owner: 'root'
     group: 'root'
     mode: '0644'
-  register: docker__register_systemd_service
+  loop: [ 'execstart-override.conf', 'http-proxy.conf' ]
+  register: docker__register_systemd_overrides
   notify: ['Restart docker' ]
   when: ansible_service_mgr == 'systemd'
   tags: [ 'role::docker:config' ]
 
-- name: Configure Docker proxy
-  template:
-    src: 'etc/systemd/system/docker.service.d/http-proxy.conf.j2'
-    dest: '/etc/systemd/system/docker.service.d/http-proxy.conf'
-    owner: 'root'
-    group: 'root'
-    mode: '0644'
-  register: docker__register_systemd_proxy_present
-  notify: ['Restart docker' ]
-  when: (ansible_service_mgr == 'systemd' and
-        (docker__env_http_proxy is defined or docker__env_https_proxy is defined))
-  tags: [ 'role::docker:config' ]
-
 - name: Reload systemd daemons
   systemd:
     daemon_reload: True
   when: (ansible_service_mgr == 'systemd' and
-         ((docker__register_systemd_service|d() and
-         docker__register_systemd_service is changed) or
-         (docker__register_systemd_proxy_present|d() and
-         docker__register_systemd_proxy_present is changed) or
-         (docker__register_systemd_proxy_absent|d() and
-         docker__register_systemd_proxy_absent is changed)))
+         docker__register_systemd_overrides is changed)
   tags: [ 'role::docker:config' ]
 
 - name: Add specified users to 'docker' group

ansible/roles/debops.docker/templates/etc/systemd/system/docker.service.d/execstart-override.conf.j2

@@ -0,0 +1,8 @@
+# {{ ansible_managed }}
+
+# Override the default ExecStart= option that comes with the upstream Docker
+# systemd unit. The socket configuration is specified in the 'daemon.json'
+# configuration file.
+[Service]
+ExecStart=
+ExecStart=/usr/bin/dockerd