snapshots: Handle installation on non-btrfs filesystems

Fixes #1147

Signed-off-by: Joseph Nuthalapati <njoseph@thoughtworks.com>
Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

plinth/modules/snapshot/__init__.py

@@ -18,13 +18,14 @@
 FreedomBox app to manage filesystem snapshots.
 """
 
-import augeas
 import json
 
+import augeas
 from django.utils.translation import ugettext_lazy as _
 
 from plinth import actions
 from plinth.menu import main_menu
+from plinth.modules import storage
 
 from .manifest import backup
 
@@ -54,6 +55,8 @@ manual_page = 'Snapshots'
 
 DEFAULT_FILE = '/etc/default/snapper'
 
+fs_types_supported = ['btrfs']
+
 
 def init():
     """Initialize the module."""
@@ -61,12 +64,19 @@ def init():
     menu.add_urlname(name, 'glyphicon-film', 'snapshot:index')
 
 
+def is_supported():
+    """Return whether snapshots are support on current setup."""
+    fs_type = storage.get_filesystem_type()
+    return fs_type in fs_types_supported
+
+
 def setup(helper, old_version=None):
     """Install and configure the module."""
     helper.install(managed_packages)
-    helper.call(
-        'post', actions.superuser_run, 'snapshot',
-        ['setup', '--old-version', str(old_version)])
+    if is_supported():
+        helper.call('post', actions.superuser_run, 'snapshot',
+                    ['setup', '--old-version',
+                     str(old_version)])
 
 
 def load_augeas():

plinth/modules/snapshot/templates/snapshot_not_supported.html

@@ -0,0 +1,32 @@
+{% extends "service-subsubmenu.html" %}
+{% comment %}
+#
+# This file is part of FreedomBox.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+{% endcomment %}
+
+{% load bootstrap %}
+{% load i18n %}
+
+{% block configuration %}
+  <div class="alert alert-danger">
+    {% blocktrans trimmed with fs_types_supported|join:', ' as types_supported %}
+      Your have a filesystem of type <strong>{{ fs_type }}</strong>. Snapshots
+      are currently only available on <strong>{{ types_supported }}</strong>
+      filesystems.
+    {% endblocktrans %}
+  </div>
+{% endblock %}

plinth/modules/snapshot/views.py

@@ -30,6 +30,7 @@ from django.utils.translation import ugettext_lazy
 from plinth import actions
 from plinth.errors import ActionError
 from plinth.modules import snapshot as snapshot_module
+from plinth.modules import storage
 
 from . import get_configuration
 from .forms import SnapshotForm
@@ -43,8 +44,24 @@ subsubmenu = [{
 }]
 
 
+def not_supported_view(request):
+    """Show that snapshots are not supported on the system."""
+    template_data = {
+        'title': snapshot_module.name,
+        'description': snapshot_module.description,
+        'fs_type': storage.get_filesystem_type(),
+        'fs_types_supported': snapshot_module.fs_types_supported,
+        'manual_page': snapshot_module.manual_page,
+    }
+    return TemplateResponse(request, 'snapshot_not_supported.html',
+                            template_data)
+
+
 def index(request):
     """Show snapshot list."""
+    if not snapshot_module.is_supported():
+        return not_supported_view(request)
+
     status = get_configuration()
     if request.method == 'POST':
         form = SnapshotForm(request.POST)
@@ -66,6 +83,9 @@ def index(request):
 
 def manage(request):
     """Show snapshot list."""
+    if not snapshot_module.is_supported():
+        return not_supported_view(request)
+
     if request.method == 'POST':
         if 'create' in request.POST:
             actions.superuser_run('snapshot', ['create'])
@@ -128,10 +148,10 @@ def update_configuration(request, old_status, new_status):
 
         messages.success(request, _('Storage snapshots configuration updated'))
     except ActionError as exception:
-        messages.error(request,
-                       _('Action error: {0} [{1}] [{2}]').format(
-                           exception.args[0], exception.args[1],
-                           exception.args[2]))
+        messages.error(
+            request,
+            _('Action error: {0} [{1}] [{2}]').format(
+                exception.args[0], exception.args[1], exception.args[2]))
 
 
 def delete_selected(request):

plinth/modules/storage/__init__.py

@@ -21,10 +21,11 @@ import json
 import logging
 import subprocess
 
+import psutil
 from django.utils.translation import ugettext_lazy as _
 
-from plinth import service as service_module
 from plinth import action_utils, actions, cfg
+from plinth import service as service_module
 from plinth.errors import PlinthError
 from plinth.menu import main_menu
 from plinth.utils import format_lazy, import_from_gi, is_user_admin
@@ -132,6 +133,15 @@ def _get_disks_from_lsblk():
     return disks
 
 
+def get_filesystem_type(mount_point='/'):
+    """Returns the type of the filesystem mounted at mountpoint."""
+    for partition in psutil.disk_partitions():
+        if partition.mountpoint == mount_point:
+            return partition.fstype
+
+    raise ValueError('No such mount point')
+
+
 def get_disk_info(mountpoint, request):
     """Get information about the free space of a drive"""
     if not is_user_admin(request, cached=True):