snapshot: Improved messages and minor refactoring

- Make the default snapshot detection slightly more robust and refactor.

- Expand description to explain automatic snapshotting, etc.

- Show description even after setup.

- Show default snapshot as a bootstrap label.

- Message explaing how rollback can be undone.

- Minor updates to delete/rollback confirmation messages.

- Minor style refactoring

actions/snapshot

@@ -85,17 +85,27 @@ def subcommand_list(_):
         parts = [part.strip() for part in line.split('|')]
         snapshots.append(dict(zip(keys, parts)))
 
-    # Mark default subvolume.
+    default = _get_default_snapshot()
+    for snapshot in snapshots:
+        snapshot['is_default'] = (snapshot['number'] == default)
+
+    print(json.dumps(snapshots))
+
+
+def _get_default_snapshot():
+    """Return the default snapshot by looking at default subvolume."""
     command = ['btrfs', 'subvolume', 'get-default', '/']
     process = subprocess.run(command, stdout=subprocess.PIPE, check=True)
     output = process.stdout.decode()
-    default = None
-    if '.snapshots' in output:
-        default = output.split('/')[1]
-    for snapshot in snapshots:
-        snapshot['is_default'] = snapshot['number'] == default
 
-    print(json.dumps(snapshots))
+    output_parts = output.split()
+    if len(output_parts) >= 9:
+        path = output.split()[8]
+        path_parts = path.split('/')
+        if len(path_parts) == 3 and path_parts[0] == '.snapshots':
+            return path_parts[1]
+
+    return None
 
 
 def subcommand_create(_):

plinth/modules/snapshot/__init__.py

@@ -35,7 +35,16 @@ title = _('Snapshots')
 
 description = [
     _('Snapshots allows creating and managing filesystem snapshots. These can '
-      'be used to roll back the system to a previous state.')
+      'be used to roll back the system to a previously known good state in '
+      'case of unwanted changes to the system.'),
+
+    _('Automatic snapshots are taken every hour, day, month and year. Older '
+      'snapshots are automatically deleted keeping 10 of each kind and 50 in '
+      'total. Although snapshots are efficient and only store the '
+      'differences, they may be deleted to reclaim free space.  Individual '
+      'files from older snapshots can be accessed by visiting ".snapshots" '
+      'directory in the filesystem. Snapshots are not a replacement for '
+      'backups.')
 ]
 
 service = None

plinth/modules/snapshot/templates/snapshot.html

@@ -1,4 +1,4 @@
-{% extends "base.html" %}
+{% extends "simple_service.html" %}
 {% comment %}
 #
 # This file is part of Plinth.
@@ -21,55 +21,58 @@
 {% load bootstrap %}
 {% load i18n %}
 
-{% block content %}
+{% block configuration %}
-  <h2>{{ title }}</h2>
 
   <div class="row">
     <div class="col-lg-8">
       <table class="table table-bordered table-condensed table-striped">
-	<thead>
+        <thead>
-	  <th>{% trans "Number" %}</th>
+          <th>{% trans "Number" %}</th>
-	  <th>{% trans "Date" %}</th>
+          <th>{% trans "Date" %}</th>
-	  <th>{% trans "Description" %}</th>
+          <th>{% trans "Description" %}</th>
-	  <th>{% trans "Rollback" %}</th>
+          <th>{% trans "Rollback" %}</th>
-	  <th>{% trans "Delete" %}</th>
+          <th>{% trans "Delete" %}</th>
-	</thead>
+        </thead>
-	<tbody>
+        <tbody>
-	  {% for snapshot in snapshots %}
+          {% for snapshot in snapshots %}
-	    {% if snapshot.description != "current" %}
+            {% if snapshot.description != "current" %}
-	      <tr>
+              <tr>
-		<td>{{ snapshot.number }}</td>
+                <td>
-		<td>{{ snapshot.date }}</td>
+                  {{ snapshot.number }}
-		<td>
+                  {% if snapshot.is_default %}
-		  {% if snapshot.is_default %}
+                    <span class="label label-primary">
-	            {% trans "[default subvolume]" %}<br />
+                      {% trans "active" %}
-		  {% endif %}
+                    </span>
-		  {{ snapshot.description }}
+                  {% endif %}
-		</td>
+                </td>
-		<td>
+                <td>{{ snapshot.date }}</td>
-		  <a href="{% url 'snapshot:rollback' snapshot.number %}"
+                <td>{{ snapshot.description }}</td>
-		     class="btn btn-default btn-sm"
+                <td>
-		     role="button"
+                  <a href="{% url 'snapshot:rollback' snapshot.number %}"
-		     title="{% blocktrans with number=snapshot.number %}Rollback to snapshot #{{ number }}{% endblocktrans %}">
+                     class="btn btn-default btn-sm" role="button"
-		    <span class="glyphicon glyphicon-repeat"
+                     title="{% blocktrans trimmed with number=snapshot.number %}
-			  aria-hidden="true"></span>
+                              Rollback to snapshot #{{ number }}
-		  </a>
+                            {% endblocktrans %}">
-		</td>
+                    <span class="glyphicon glyphicon-repeat"
-		<td>
+                          aria-hidden="true"></span>
-		  {% if not snapshot.is_default %}
+                  </a>
-		  <a href="{% url 'snapshot:delete' snapshot.number %}"
+                </td>
-		     class="btn btn-default btn-sm"
+                <td>
-		     role="button"
+                  {% if not snapshot.is_default %}
-		     title="{% blocktrans with number=snapshot.number %}Delete snapshot #{{ number }}{% endblocktrans %}">
+                    <a href="{% url 'snapshot:delete' snapshot.number %}"
-		    <span class="glyphicon glyphicon-trash"
+                       class="btn btn-default btn-sm" role="button"
-			  aria-hidden="true"></span>
+                       title="{% blocktrans trimmed with number=snapshot.number %}
-		  </a>
+                                Delete snapshot #{{ number }}
-		  {% endif %}
+                              {% endblocktrans %}">
-		</td>
+                      <span class="glyphicon glyphicon-trash"
-	      </tr>
+                            aria-hidden="true"></span>
-	    {% endif %}
+                    </a>
-	  {% endfor %}
+                  {% endif %}
-	</tbody>
+                </td>
+              </tr>
+            {% endif %}
+          {% endfor %}
+        </tbody>
       </table>
     </div>
   </div>
@@ -79,7 +82,8 @@
       {% csrf_token %}
 
       <input type="submit" class="btn btn-primary"
-	     value="{% trans "Create Snapshot" %}"/>
+             value="{% trans "Create Snapshot" %}"/>
     </form>
   </p>
+
 {% endblock %}

plinth/modules/snapshot/templates/snapshot_delete.html

@@ -24,11 +24,7 @@
 {% block content %}
   <h2>{{ title }}</h2>
 
-  <p>
+  <p>{% trans "Delete this snapshot permanently?" %}</p>
-    {% blocktrans trimmed %}
-    The snapshot will be permanently deleted. Please confirm.
-    {% endblocktrans %}
-  </p>
 
   <div class="row">
     <div class="col-lg-8">
@@ -54,7 +50,9 @@
       {% csrf_token %}
 
       <input type="submit" class="btn btn-primary"
-             value="{% blocktrans with number=snapshot.number %}Delete Snapshot #{{ number }}{% endblocktrans %}"/>
+             value="{% blocktrans trimmed with number=snapshot.number %}
+                      Delete Snapshot #{{ number }}
+                    {% endblocktrans %}"/>
     </form>
   </p>
 

plinth/modules/snapshot/templates/snapshot_rollback.html

@@ -24,9 +24,13 @@
 {% block content %}
   <h2>{{ title }}</h2>
 
+  <p>{% trans "Roll back the system to this snapshot?" %}</p>
+
   <p>
     {% blocktrans trimmed %}
-    The system will be rolled back to the selected snapshot. Please confirm.
+      A new snapshot with the current state of the file system will be
+      automatically created. You will be able to undo a rollback by
+      reverting to the newly created snapshot.
     {% endblocktrans %}
   </p>
 
@@ -54,7 +58,9 @@
       {% csrf_token %}
 
       <input type="submit" class="btn btn-primary"
-             value="{% blocktrans with number=snapshot.number %}Rollback to Snapshot #{{ number }}{% endblocktrans %}"/>
+             value="{% blocktrans trimmed with number=snapshot.number %}
+                      Rollback to Snapshot #{{ number }}
+                    {% endblocktrans %}"/>
     </form>
   </p>
 

plinth/modules/snapshot/views.py

@@ -41,6 +41,7 @@ def index(request):
 
     return TemplateResponse(request, 'snapshot.html',
                             {'title': snapshot_module.title,
+                             'description': snapshot_module.description,
                              'snapshots': snapshots})
 
 
@@ -48,16 +49,17 @@ def delete(request, number):
     """Show confirmation to delete a snapshot."""
     if request.method == 'POST':
         actions.superuser_run('snapshot', ['delete', number])
-        messages.success(request, _('Deleted snapshot.'))
+        messages.success(
+            request, _('Deleted snapshot #{number}.').format(number=number))
         return redirect(reverse('snapshot:index'))
 
     output = actions.superuser_run('snapshot', ['list'])
     snapshots = json.loads(output)
 
     snapshot = None
-    for s in snapshots:
+    for current_snapshot in snapshots:
-        if s['number'] == number:
+        if current_snapshot['number'] == number:
-            snapshot = s
+            snapshot = current_snapshot
 
     return TemplateResponse(request, 'snapshot_delete.html',
                             {'title': _('Delete Snapshot'),
@@ -68,7 +70,9 @@ def rollback(request, number):
     """Show confirmation to rollback to a snapshot."""
     if request.method == 'POST':
         actions.superuser_run('snapshot', ['rollback', number])
-        messages.success(request, _('Set default subvolume for rollback.'))
+        messages.success(
+            request,
+            _('Rolled back to snapshot #{number}.').format(number=number))
         messages.warning(
             request,
             _('The system must be restarted to complete the rollback.'))
@@ -78,9 +82,9 @@ def rollback(request, number):
     snapshots = json.loads(output)
 
     snapshot = None
-    for s in snapshots:
+    for current_snapshot in snapshots:
-        if s['number'] == number:
+        if current_snapshot['number'] == number:
-            snapshot = s
+            snapshot = current_snapshot
 
     return TemplateResponse(request, 'snapshot_rollback.html',
                             {'title': _('Rollback to Snapshot'),