Add virt-builder source

Add implementation for virt-builder source which aims to create
container root file system from VM image build with virt-builder.

Usage examples:
    $ virt-bootstrap virt-builder://fedora-25 /tmp/foo
    $ virt-bootstrap virt-builder://ubuntu-16.04 /tmp/bar --root-password secret
    $ virt-bootstrap virt-builder://fedora-25 /tmp/foo -f qcow2 --idmap 0:1000:10
    $ sudo virt-bootstrap virt-builder://fedora-25 /tmp/foo --idmap 0:1000:10

Tests are also introduced along with the implementation. They cover
creation of root file system and UID/GID mapping for 'dir' and 'qcow2'
output format by mocking the build_image() method to avoid the time
consuming call to virt-builder which might also require network
connection with function which creates dummy disk image.
Setting root password is handled by virt-builder and hence the
introduced test only ensures that the password string is passed
correctly.

3 files changed, 156 insertions, 1 deletions

diff --git a/src/virtBootstrap/sources/__init__.py b/src/virtBootstrap/sources/__init__.py
index e891e9b..be6b25c 100644
--- a/src/virtBootstrap/sources/__init__.py
+++ b/src/virtBootstrap/sources/__init__.py
@@ -24,3 +24,4 @@ sources - Class definitions which process container image or
 
 from virtBootstrap.sources.file_source import FileSource
 from virtBootstrap.sources.docker_source import DockerSource
+from virtBootstrap.sources.virt_builder_source import VirtBuilderSource
diff --git a/src/virtBootstrap/sources/virt_builder_source.py b/src/virtBootstrap/sources/virt_builder_source.py
new file mode 100644
index 0000000..628544f
--- /dev/null
+++ b/src/virtBootstrap/sources/virt_builder_source.py
@@ -0,0 +1,154 @@
+# -*- coding: utf-8 -*-
+# Authors: Radostin Stoyanov <rstoyanov1@gmail.com>
+#
+# Copyright (C) 2017 Radostin Stoyanov
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU 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 General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+VirtBuilderSource aim is to extract the root file system from VM image
+build with virt-builder from template.
+"""
+
+import os
+import logging
+import subprocess
+import tempfile
+
+import guestfs
+from virtBootstrap import utils
+
+
+# pylint: disable=invalid-name
+# Create logger
+logger = logging.getLogger(__name__)
+
+
+class VirtBuilderSource(object):
+    """
+    Extract root file system from image build with virt-builder.
+    """
+    def __init__(self, **kwargs):
+        """
+        Create container rootfs by building VM from virt-builder template
+        and extract the rootfs.
+
+        @param uri: Template name
+        @param fmt: Format used to store the output [dir, qcow2]
+        @param uid_map: Mappings for UID of files in rootfs
+        @param gid_map: Mappings for GID of files in rootfs
+        @param root_password: Root password to set in rootfs
+        @param progress: Instance of the progress module
+        """
+        # Parsed URIs:
+        # - "virt-builder:///<template>"
+        # - "virt-builder://<template>"
+        # - "virt-builder:/<template>"
+        self.template = kwargs['uri'].netloc or kwargs['uri'].path[1:]
+        self.output_format = kwargs.get('fmt', utils.DEFAULT_OUTPUT_FORMAT)
+        self.uid_map = kwargs.get('uid_map', [])
+        self.gid_map = kwargs.get('gid_map', [])
+        self.root_password = kwargs.get('root_password', None)
+        self.progress = kwargs['progress'].update_progress
+
+    def build_image(self, output_file):
+        """
+        Build VM from virt-builder template
+        """
+        cmd = ['virt-builder', self.template,
+               '-o', output_file,
+               '--no-network',
+               '--delete', '/dev/*',
+               '--delete', '/boot/*',
+               # Comment out all lines in fstab
+               '--edit', '/etc/fstab:s/^/#/']
+        if self.root_password is not None:
+            cmd += ['--root-password', "password:%s" % self.root_password]
+        self.run_builder(cmd)
+
+    def run_builder(self, cmd):
+        """
+        Execute virt-builder command
+        """
+        subprocess.check_call(cmd)
+
+    def unpack(self, dest):
+        """
+        Build image and extract root file system
+
+        @param dest: Directory path where output files will be stored.
+        """
+
+        with tempfile.NamedTemporaryFile(prefix='bootstrap_') as tmp_file:
+            if self.output_format == 'dir':
+                self.progress("Building image", value=0, logger=logger)
+                self.build_image(tmp_file.name)
+                self.progress("Extracting rootfs", value=50, logger=logger)
+                g = guestfs.GuestFS(python_return_dict=True)
+                g.add_drive_opts(tmp_file.name, readonly=False, format='raw')
+                g.launch()
+
+                # Get the device with file system
+                root_dev = g.inspect_os()
+                if not root_dev:
+                    raise Exception("No file system was found")
+                g.mount(root_dev[0], '/')
+
+                # Extract file system to destination directory
+                g.copy_out('/', dest)
+
+                g.umount('/')
+                g.shutdown()
+
+                self.progress("Extraction completed successfully!",
+                              value=100, logger=logger)
+                logger.info("Files are stored in: %s", dest)
+
+            elif self.output_format == 'qcow2':
+                output_file = os.path.join(dest, 'layer-0.qcow2')
+
+                self.progress("Building image", value=0, logger=logger)
+                self.build_image(tmp_file.name)
+
+                self.progress("Extracting rootfs", value=50, logger=logger)
+                g = guestfs.GuestFS(python_return_dict=True)
+                g.add_drive_opts(tmp_file.name, readonly=True, format='raw')
+                # Create qcow2 disk image
+                g.disk_create(
+                    filename=output_file,
+                    format='qcow2',
+                    size=os.path.getsize(tmp_file.name)
+                )
+                g.add_drive_opts(output_file, readonly=False, format='qcow2')
+                g.launch()
+                # Get the device with file system
+                root_dev = g.inspect_os()
+                if not root_dev:
+                    raise Exception("No file system was found")
+                output_dev = g.list_devices()[1]
+                # Copy the file system to the new qcow2 disk
+                g.copy_device_to_device(root_dev[0], output_dev, sparse=True)
+                g.shutdown()
+
+                # UID/GID mapping
+                if self.uid_map or self.gid_map:
+                    logger.info("Mapping UID/GID")
+                    utils.map_id_in_image(1, dest, self.uid_map, self.gid_map)
+
+                self.progress("Extraction completed successfully!", value=100,
+                              logger=logger)
+                logger.info("Image is stored in: %s", output_file)
+
+            else:
+                raise Exception("Unknown format:" + self.output_format)
diff --git a/src/virtBootstrap/virt_bootstrap.py b/src/virtBootstrap/virt_bootstrap.py
index e387842..fe95f5e 100755
--- a/src/virtBootstrap/virt_bootstrap.py
+++ b/src/virtBootstrap/virt_bootstrap.py
@@ -62,7 +62,7 @@ def get_source(source_type):
     Get object which match the source type
     """
     try:
-        class_name = "%sSource" % source_type.capitalize()
+        class_name = "%sSource" % source_type.title().replace('-', '')
         clazz = getattr(sources, class_name)
         return clazz
     except Exception: