snapshot: New module for disk snapshots

- Create and list filesystem snapshots. Hide "current" snapshot.

- Allow deleting snapshots, except for default subvolume.

- Allow rollback to a snapshot.

actions/snapshot

@@ -0,0 +1,130 @@
+#!/usr/bin/python3
+#
+# This file is part of Plinth.
+#
+# 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/>.
+#
+
+"""
+Configuration helper for filesystem snapshots.
+"""
+
+import argparse
+import json
+import subprocess
+
+FSTAB = '/etc/fstab'
+
+
+def parse_arguments():
+    """Return parsed command line arguments as dictionary."""
+    parser = argparse.ArgumentParser()
+    subparsers = parser.add_subparsers(dest='subcommand', help='Sub command')
+
+    subparsers.add_parser('setup', help='Configure snapper')
+    subparsers.add_parser('list', help='List snapshots')
+    subparsers.add_parser('create', help='Create snapshot')
+
+    subparser = subparsers.add_parser('delete', help='Delete snapshot')
+    subparser.add_argument('number', help='Number of snapshot to delete')
+
+    subparser = subparsers.add_parser('rollback', help='Rollback to snapshot')
+    subparser.add_argument('number', help='Number of snapshot to rollback to')
+
+    return parser.parse_args()
+
+
+def subcommand_setup(_):
+    """Configure snapper."""
+    # Check if root config exists.
+    command = ['snapper', 'list-configs']
+    process = subprocess.run(command, stdout=subprocess.PIPE, check=True)
+    output = process.stdout.decode()
+
+    # Create root config if needed.
+    if 'root' not in output:
+        command = ['snapper', 'create-config', '/']
+        subprocess.run(command, check=True)
+
+    # Add mountpoint for subvolumes.
+    with open(FSTAB, 'r') as fstab:
+        lines = fstab.readlines()
+
+    spec = None
+    for line in lines:
+        if '.snapshots' in line:
+            return
+        if 'btrfs' in line:
+            spec = line.split(' ')[0]
+
+    if spec:
+        with open(FSTAB, 'a') as fstab:
+            fstab.write(spec + ' /.snapshots btrfs subvol=.snapshots 0 1\n')
+
+
+def subcommand_list(_):
+    """List snapshots."""
+    command = ['snapper', 'list']
+    process = subprocess.run(command, stdout=subprocess.PIPE, check=True)
+    lines = process.stdout.decode().splitlines()
+    keys = ('type', 'number', 'pre_number', 'date', 'user', 'cleanup',
+            'description')
+    snapshots = []
+    for line in lines[2:]:
+        parts = [part.strip() for part in line.split('|')]
+        snapshots.append(dict(zip(keys, parts)))
+
+    # Mark 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))
+
+
+def subcommand_create(_):
+    """Create snapshot."""
+    command = ['snapper', 'create', '--description', 'manually created']
+    subprocess.run(command, check=True)
+
+
+def subcommand_delete(arguments):
+    """Delete snapshot."""
+    command = ['snapper', 'delete', arguments.number]
+    subprocess.run(command, check=True)
+
+
+def subcommand_rollback(arguments):
+    """Rollback to snapshot."""
+    command = ['snapper', 'rollback', '--description', 'created by rollback',
+               arguments.number]
+    subprocess.run(command, check=True)
+
+
+def main():
+    """Parse arguments and perform all duties."""
+    arguments = parse_arguments()
+
+    subcommand = arguments.subcommand.replace('-', '_')
+    subcommand_method = globals()['subcommand_' + subcommand]
+    subcommand_method(arguments)
+
+
+if __name__ == '__main__':
+    main()

data/etc/plinth/modules-enabled/snapshot

@@ -0,0 +1 @@
+plinth.modules.snapshot

plinth/modules/snapshot/__init__.py

@@ -0,0 +1,53 @@
+#
+# This file is part of Plinth.
+#
+# 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/>.
+#
+
+"""
+Plinth module to manage filesystem snapshots.
+"""
+
+from django.utils.translation import ugettext_lazy as _
+
+from plinth import actions
+from plinth import cfg
+
+
+version = 1
+
+depends = ['system']
+
+managed_packages = ['snapper']
+
+title = _('Snapshots')
+
+description = [
+    _('Snapshots allows creating and managing filesystem snapshots. These can '
+      'be used to roll back the system to a previous state.')
+]
+
+service = None
+
+
+def init():
+    """Initialize the module."""
+    menu = cfg.main_menu.get('system:index')
+    menu.add_urlname(title, 'glyphicon-film', 'snapshot:index')
+
+
+def setup(helper, old_version=None):
+    """Install and configure the module."""
+    helper.install(managed_packages)
+    helper.call('post', actions.superuser_run, 'snapshot', ['setup'])

plinth/modules/snapshot/templates/snapshot.html

@@ -0,0 +1,85 @@
+{% extends "base.html" %}
+{% comment %}
+#
+# This file is part of Plinth.
+#
+# 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 content %}
+  <h2>{{ title }}</h2>
+
+  <div class="row">
+    <div class="col-lg-8">
+      <table class="table table-bordered table-condensed table-striped">
+	<thead>
+	  <th>{% trans "Number" %}</th>
+	  <th>{% trans "Date" %}</th>
+	  <th>{% trans "Description" %}</th>
+	  <th>{% trans "Rollback" %}</th>
+	  <th>{% trans "Delete" %}</th>
+	</thead>
+	<tbody>
+	  {% for snapshot in snapshots %}
+	    {% if snapshot.description != "current" %}
+	      <tr>
+		<td>{{ snapshot.number }}</td>
+		<td>{{ snapshot.date }}</td>
+		<td>
+		  {% if snapshot.is_default %}
+	            {% trans "[default subvolume]" %}<br />
+		  {% endif %}
+		  {{ snapshot.description }}
+		</td>
+		<td>
+		  <a href="{% url 'snapshot:rollback' snapshot.number %}"
+		     class="btn btn-default btn-sm"
+		     role="button"
+		     title="{% blocktrans with number=snapshot.number %}Rollback to snapshot #{{ number }}{% endblocktrans %}">
+		    <span class="glyphicon glyphicon-repeat"
+			  aria-hidden="true"></span>
+		  </a>
+		</td>
+		<td>
+		  {% if not snapshot.is_default %}
+		  <a href="{% url 'snapshot:delete' snapshot.number %}"
+		     class="btn btn-default btn-sm"
+		     role="button"
+		     title="{% blocktrans with number=snapshot.number %}Delete snapshot #{{ number }}{% endblocktrans %}">
+		    <span class="glyphicon glyphicon-trash"
+			  aria-hidden="true"></span>
+		  </a>
+		  {% endif %}
+		</td>
+	      </tr>
+	    {% endif %}
+	  {% endfor %}
+	</tbody>
+      </table>
+    </div>
+  </div>
+
+  <p>
+    <form class="form" method="post">
+      {% csrf_token %}
+
+      <input type="submit" class="btn btn-primary"
+	     value="{% trans "Create Snapshot" %}"/>
+    </form>
+  </p>
+{% endblock %}

plinth/modules/snapshot/templates/snapshot_delete.html

@@ -0,0 +1,61 @@
+{% extends "base.html" %}
+{% comment %}
+#
+# This file is part of Plinth.
+#
+# 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 content %}
+  <h2>{{ title }}</h2>
+
+  <p>
+    {% blocktrans trimmed %}
+    The snapshot will be permanently deleted. Please confirm.
+    {% endblocktrans %}
+  </p>
+
+  <div class="row">
+    <div class="col-lg-8">
+      <table class="table table-bordered table-condensed table-striped">
+	<thead>
+	  <th>{% trans "Number" %}</th>
+	  <th>{% trans "Date" %}</th>
+	  <th>{% trans "Description" %}</th>
+	</thead>
+	<tbody>
+	  <tr>
+	    <td>{{ snapshot.number }}</td>
+	    <td>{{ snapshot.date }}</td>
+	    <td>{{ snapshot.description }}</td>
+	  </tr>
+	</tbody>
+      </table>
+    </div>
+  </div>
+
+  <p>
+    <form class="form" method="post">
+      {% csrf_token %}
+
+      <input type="submit" class="btn btn-primary"
+             value="{% blocktrans with number=snapshot.number %}Delete Snapshot #{{ number }}{% endblocktrans %}"/>
+    </form>
+  </p>
+
+{% endblock %}

plinth/modules/snapshot/templates/snapshot_rollback.html

@@ -0,0 +1,61 @@
+{% extends "base.html" %}
+{% comment %}
+#
+# This file is part of Plinth.
+#
+# 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 content %}
+  <h2>{{ title }}</h2>
+
+  <p>
+    {% blocktrans trimmed %}
+    The system will be rolled back to the selected snapshot. Please confirm.
+    {% endblocktrans %}
+  </p>
+
+  <div class="row">
+    <div class="col-lg-8">
+      <table class="table table-bordered table-condensed table-striped">
+	<thead>
+	  <th>{% trans "Number" %}</th>
+	  <th>{% trans "Date" %}</th>
+	  <th>{% trans "Description" %}</th>
+	</thead>
+	<tbody>
+	  <tr>
+	    <td>{{ snapshot.number }}</td>
+	    <td>{{ snapshot.date }}</td>
+	    <td>{{ snapshot.description }}</td>
+	  </tr>
+	</tbody>
+      </table>
+    </div>
+  </div>
+
+  <p>
+    <form class="form" method="post">
+      {% csrf_token %}
+
+      <input type="submit" class="btn btn-primary"
+             value="{% blocktrans with number=snapshot.number %}Rollback to Snapshot #{{ number }}{% endblocktrans %}"/>
+    </form>
+  </p>
+
+{% endblock %}

plinth/modules/snapshot/urls.py

@@ -0,0 +1,32 @@
+#
+# This file is part of Plinth.
+#
+# 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/>.
+#
+
+"""
+URLs for the snapshot module.
+"""
+
+from django.conf.urls import url
+
+from . import views
+
+
+urlpatterns = [
+    url(r'^sys/snapshot/$', views.index, name='index'),
+    url(r'^sys/snapshot/(?P<number>\d+)/delete$', views.delete, name='delete'),
+    url(r'^sys/snapshot/(?P<number>\d+)/rollback$', views.rollback,
+        name='rollback'),
+]

plinth/modules/snapshot/views.py

@@ -0,0 +1,87 @@
+#
+# This file is part of Plinth.
+#
+# 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/>.
+#
+
+"""
+Views for snapshot module.
+"""
+
+from django.contrib import messages
+from django.core.urlresolvers import reverse
+from django.shortcuts import redirect
+from django.template.response import TemplateResponse
+from django.utils.translation import ugettext as _
+import json
+
+from plinth import actions
+from plinth.modules import snapshot as snapshot_module
+
+
+def index(request):
+    """Show snapshot list."""
+    if request.method == 'POST':
+        actions.superuser_run('snapshot', ['create'])
+        messages.success(request, _('Created snapshot.'))
+
+    output = actions.superuser_run('snapshot', ['list'])
+    snapshots = json.loads(output)
+
+    return TemplateResponse(request, 'snapshot.html',
+                            {'title': snapshot_module.title,
+                             'snapshots': snapshots})
+
+
+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.'))
+        return redirect(reverse('snapshot:index'))
+
+    output = actions.superuser_run('snapshot', ['list'])
+    snapshots = json.loads(output)
+
+    snapshot = None
+    for s in snapshots:
+        if s['number'] == number:
+            snapshot = s
+
+    return TemplateResponse(request, 'snapshot_delete.html',
+                            {'title': _('Delete Snapshot'),
+                             'snapshot': snapshot})
+
+
+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.warning(
+            request,
+            _('The system must be restarted to complete the rollback.'))
+        return redirect(reverse('power:restart'))
+
+    output = actions.superuser_run('snapshot', ['list'])
+    snapshots = json.loads(output)
+
+    snapshot = None
+    for s in snapshots:
+        if s['number'] == number:
+            snapshot = s
+
+    return TemplateResponse(request, 'snapshot_rollback.html',
+                            {'title': _('Rollback to Snapshot'),
+                             'snapshot': snapshot})